Hydraulic Cylinder Honing {7562} Caterpillar

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Introduction

Table 1

Revision	Summary of Changes in REHS2689
29	Updated Effectivity
28	Minor edits and updated surface finish specifications Added new Notice above Reference section
27	Updated Effectivity
26	Updated Effectivity

© 2018 Caterpillar All Rights Reserved. This guideline is for the use of Caterpillar Dealers only. Unauthorized use of this document or the proprietary processes therein without permission may be violation of intellectual property law. Information contained in this document is considered Caterpillar: Confidential Yellow.

This guideline enables dealers and dealer customers to benefit from cost reductions made possible through an established parts reusability and salvage program. Every effort has been made to provide the most current information known to Caterpillar Inc. Since the company makes ongoing product changes and product improvements, this guideline must be used with the latest technical information. Using the latest technical information available from Caterpillar ensures that such changes and improvements are incorporated where applicable.

For questions or additional information concerning this guideline, submit a feedback form in the Service Information System web site. to address an urgent need, use the following to forward your request to Caterpillar Repair Process Engineering:

• Cat Dealer Technical Communicator

• Global Dealer Solution Network

• Cat Technical Representative

• Knowledge Network

Canceled Part Numbers and Replaced Part Numbers

This document may not include canceled part numbers and replaced part numbers. Use NPR on SIS for information about canceled part numbers and replaced part numbers. NPR will provide the current part numbers for replaced parts.

Summary

This guideline will discuss general procedures and practices for hydraulic cylinder honing. The hones shown in this document are no longer available from Caterpillar. Always refer to the correct tool operating manual for the hone that you are using.

During a cylinder repair honing the cylinder is important. Honing ensures that the proper surface finish is achieved on the cylinder walls. Honing creates the proper sealing surface for new seals.

Hydraulic cylinders are honed to ensure that the proper surface finish is restored on the cylinder walls. Honing also brings the cylinder bore back to the correct size and roundness. Another purpose of hydraulic cylinder honing is refinishing the bore that has been in previous service.

Refinishing involves the removal of scratches and/or rust that is on the cylinder walls. An improper surface finish will prevent new seals from providing a good seal on the cylinder wall. The cylinder may leak and unexpected performance might occur. The surface roughness needs to be within a specified range. If the surface is too rough, the seal will not last for the intended life. If the surface is too smooth, proper oil retention on the cylinder walls will be inadequate. The seal may get hot due to friction which is a cause of premature failure.

Honing is used to scuff a smooth or glazed cylinder surface. Honing gives the cylinder a texture that will hold oil. Honing also provides lubrication for the piston seal and the wear ring. Honing will also correct noticeable distortion in cylinder bores such as out of round, bell mouth, barrel, taper, and minor dents.

All cylinders that are honed in accordance with this guideline should meet the specifications of the manufacturer. The cylinders that are properly honed should function correctly until the next overhaul. Do not reuse a cylinder if Special Instruction, SEBF8072, "Inspection and Salvage of Hydraulic Cylinder Components" indicates otherwise. If a cylinder fails due to abnormal wear, the problem should be fixed prior to honing. A cylinder that is deemed unusable by this guideline should not be salvaged.

Important Safety Information

Illustration 1	g02139237

Most accidents that involve product operation, maintenance, and repair are caused by failure to observe basic safety rules or precautions. An accident can often be avoided by recognizing potentially hazardous situations before an accident occurs. A person must be alert to potential hazards. This person should also have the necessary training, skills, and tools to perform these functions properly.

Improper operation, lubrication, maintenance, or repair of this product can be dangerous resulting in possible injury or death.

Do not operate or perform any lubrication, maintenance, or repair on this product until you have read the operation, lubrication, maintenance, and repair information. Safety precautions and warnings are provided in this manual and on the product. If these hazard warnings are not heeded, bodily injury or death could occur to you or to other persons.

The hazards are identified by a safety alert symbol. Safety alert symbols are followed by a signal word such as "Warning" that is shown below.

Illustration 2	g01179590

The following is the meaning of this safety alert symbol:

• Pay Attention!

• Become Alert!

• Your Safety is Involved.

The message that appears under the warning explains the hazard. The message will be written or pictorially shown.

Operations that may cause product damage are identified by "NOTICE" labels on the product and in this publication.

Caterpillar cannot anticipate every possible circumstance that might involve a potential hazard. The warnings in this publication and on the product are not all inclusive. Only use tools, procedures, work methods, or operating techniques that are recommended by Caterpillar. The safety of the product and operator must be ensured during all operations, lubrication, maintenance, or repair procedures.

The information, specifications, and illustrations in this publication are based on information that was available at the time of publication. The specifications, torque, pressures, measurements, adjustments, illustrations, and other items can change at any time. These changes can affect the service that is given to the product. Contact your Caterpillar dealer to obtain current and complete information before you start any job.

Safety

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Do not operate or work on this machine unless you have read and understand the instructions and warnings in the Operation and Maintenance Manuals. Failure to follow the instructions or heed the warnings could result in injury or death. Contact your Cat dealer for replacement manuals. Proper care is your responsibility.

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Personal injury can result from hydraulic oil pressure and hot oil. Hydraulic oil pressure can remain in the hydraulic system after the engine has been stopped. Serious injury can be caused if this pressure is not released before any service is done on the hydraulic system. Make sure all of the work tools have been lowered to the ground, and the oil is cool before removing any components or lines. Remove the oil filler cap only when the engine is stopped, and the filler cap is cool enough to touch with your bare hand.

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Personal injury or death can result from escaping fluid under pressure. Escaping fluid under pressure, even a very small pin-hole size leak, can penetrate body tissue and cause serious injury and possible death. If fluid is injected into your skin, it must be treated immediately by a doctor familiar with this type of injury. Always use a board or cardboard when checking for a leak.

Notice

For purposes of this document and work instruction, the default surface roughness parameter is Ra, roughness average. It is recognized that some suppliers of cylinder piston seals may use other parameters in addition to Ra, but satisfactory results have been obtained with Ra alone. Profilometers shall meet the requirements of ANSI/ASME B46.1 and ISO 3274, and preferably have a stylus tip radius of 2 microns. Measurements shall use an assessment length of at least 4.0 mm and cutoff length of 0.8mm.

References

Table 2

Caterpillar References
Media Number	Title
PERJ1017	"Dealer Service Tool Catalog"
SEHS9538	"Using the 9U-6463 Hone Group and Attachments"
NEHS0627	"1U-9001 and 1U-9002 Automatic Hone Tooling" (This tooling provides the 9U-6462 Manual Hone with some features of a semi-automatic hone.)
NEHS0901	"223-2225 Automatic Hydraulic Cylinder Hone" (223-2225 is a semi-automatic hone.)
SEBF8072	"Inspection and Salvage of Hydraulic Cylinder Components"
PEKP1020	"Hydraulic Cylinder & Seal Reference Guide"
NEHS0927	"Procedures for Using the 250-6597 Cylinder Washer Tank Group"
SEHS9031	"Storage Procedures for Caterpillar Products"
SEBF9238	"Fundamentals of Arc Spray for Reconditioning Components"
SEBF9240	"Fundamentals of Flame Spray for Reconditioning Components"
SEBF9236	"Fundamentals of High Velocity Oxygen Fuel (HVOF) Spray for Reconditioning Components"
Non-Caterpillar References
Source	Title
Dealer.cat.com or www.sunnen.com	Find under Product Support > Service Operations > Sunnen Products Company or Sunnen "II-HTA-240: HTA2000/4000-Series Tube Hones - IOM Instructions" (search with "HTA Operating Instructions")
www.sunnen.com	"Sunnen Honing Techniques - "Obtaining Specified Finishes by Honing"" (search under Literature)

Tooling

Table 3

Required Tools
Part Number	Part Description
1U-8809	Rust Preventative
4C-4804	Penetrating Oil
4C-4805	Developer
222-3121	Rust Preventative
185-4125	Rust Preventative
1P-3537	Dial Bore Gauge Gp
179-7056	Work Light
9U-6463	Hone Gp
5P-8615	Honing Oil
9U-6484	Honing Oil
250-6597	Cylinder Washer Gp
4C-6794	Oil
448-3697	Profilometer
448-3698	Profilometer

Cleaning and Preparation

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Personal injury can result from air pressure. Personal injury can result without following proper procedure. When using pressurized air, wear a protective face shield and protective clothing. Maximum air pressure at the nozzle must be less than 205 kPa (30 psi) for cleaning purposes.

Wash all dirt, grease, oil, and contaminants from the cylinder assembly. If the cylinder is dirty, a high-pressure washer may be required to remove all the unwanted material. Cleaning the inside and outside of the cylinder is important. To achieve an accurate inspection, the cylinder must be cleaned properly. Proper cleaning also prevents outside contamination from entering the hone oil supply.

If the cylinder is not going to be honed within two days of disassembly and cleaning, apply a generous coat of 222-3121 Rust Preventive or 1U-8809 Caterpillar 450 Rust Preventative Oil. In EAME, order 185-4125 Caterpillar 450 Rust Preventative Oil. The rust preventative prevents rust from forming on the unfinished portion of the cylinder walls.

Inspection

Perform an inspection on the cylinder before significant time is spent on the honing process. Following the proper inspection process eliminates unnecessary cylinder repairs. Inspect cylinders thoroughly to aid in the decision of future action. These actions may include having the cylinder retubed or purchasing a remanufactured cylinder from Caterpillar.

External Inspection

First, conduct an inspection of the outside of the hydraulic cylinder housing.

• Check for areas on the cylinder that have been welded by someone other than the Original Equipment Manufacturer. The tube must be removed from the cylinder assembly when an unwanted weld is present.

• Check for cracks that extend through the cylinder wall. A crack may only become visible under pressure. When this type of crack is suspected, use Caterpillar 4C-4804 Penetrant and 4C-4805 Developer to check for cracks. When a crack is present, the cylinder must be retubed or replaced.

• Check for overall condition of the cylinder tube. Inspect the outside of the cylinders for gouges. Inspect the outside of the cylinders for excessive rust pitting. Also, check for any bulges in the cylinder. When a cylinder tube has any of these conditions, the cylinder must be retubed or replaced.

• Check the condition of the port boss or flange face. Check for gouges and the overall condition of the port. If there is excessive wear or any other type of defect, the port boss or flange must be replaced.

Internal Inspection

Proper inspection of the cylinder bore is important. Proper inspection will help determine the time that is required for repair of the cylinder. This inspection will allow the total cost of the cylinder rebuild to be estimated. A determination can then be made if the cylinder is economically feasible to hone. Another alternative may be the best option to restore machine operation.

• The inside of the cylinder should be clean and free from all dirt and contaminants. Some cylinders may require cleaning prior to inspections due to excessive dirt buildup.

• On gland-type cylinders the condition of the gland and gland threads should be checked. The threads should be in good condition. A thread chaser should be used to clean the threads. A tap may also be used to clean the threads. These items can be found in the Dealer Service Tool Catalog, NENG2500.

• Use a 1P-3537 Dial Bore Gauge or an inside micrometer to determine whether the cylinder is out of round or has other bore distortions. An inside micrometer such as Starrett part number 823CZ with a 4 - 24 inch range or Starrett part number 823MEZ with a 100 - 1000 mm range can be used. A measurement will also determine if the cylinder has already been honed beyond the diameter to allow for honing. Compare the actual bore against the dimension given in the Specifications Manual for the specific machine you are working on. Depending on the diameter size over the nominal size, the tube may accommodate oversize honing. Refer to "Oversized Honing" later in this document for more instructions. Take multiple measurements around the cylinder. When there is more than 0.51 mm (0.020 inch) difference in the measurements, the cylinder is out of round and must be retubed or replaced. If the difference is less than 0.51 mm (0.020 inch), honing the tube might be possible.

Illustration 3	g01178390
Types of bore distortions.

• Check for bore distortions in the cylinder. If the cylinder has any bore distortions, proper piston to cylinder wall fit will not be adequate. Therefore the cylinder will drift and not perform correctly. There are many different types of bore distortions that can occur due to general wear and cylinder application. Refer to Illustration 3.

• Use a surface reconditioning flex-hone, also known as a ball hone, on the inside diameter of the cylinder tube. Use a hand drill and run the hone through the cylinder bore approximately 2-3 times. A hand drill will remove any buffing marks that may be on the cylinder and emphasis the actual longitudinal scratches and imperfections.

• Extreme caution must be used when using the surface reconditioning flex-hone. The proper size hone MUST be used to prevent the formation of new scratches in the cylinder bore. The hone must be operated parallel to the cylinder bore. This step prevents the hone from cutting in on one side and causing new circular scratches to be formed. Do not allow the hone to become bound up in the cylinder. The various sized ball hones are available from the Dealer Service Tool Catalog, NENG2500.

• Use a 179-7056 Inspection Light when inspecting the inside surface of a hydraulic cylinder tube.

Note: The use of a standard light or flashlight will not produce an accurate view of the cylinder tube surface. The inspection light will prevent light from bouncing off the cylinder walls and causing an inaccurate view of the actual scratch. Using an inspection light will allow for a more accurate time and cost estimate for rebuilding the cylinder.

• Inspect the inside of the cylinder wall for defects in the tube. Check for gouges, scratches, cracks, pitting, or any other type of defect that may be in the cylinder wall. The most common problem to be encountered with the cylinder will be scratches that were caused by some foreign material that entered the cylinder. The contamination can lodge between the piston and the cylinder wall. These scratches in the cylinder will be longitudinal.

• Determine the depth of the scratch. There are different methods used to determine the depth of the scratch in a hydraulic cylinder.

1. Use a profilometer. A profilometer will give you a digital readout of the surface roughness of the cylinder. A profilometer will also give you the depth of the scratch in the cylinder surface.

2. A second method of determining the severity of a scratch is to use your fingernail. If a scratch is noticeably felt with a fingernail, recondition the cylinder. If the scratch is not noticeably felt with a fingernail, reconditioning should not be required.

Note: This process is not an exact method of determining scratch depth. This process is just a guide that will approximately gauge the need for reconditioning of the cylinder. Cylinder inspection accuracy is something a person will gain with experience. Over time, most experienced technicians can determine the approximate scratch depth with a visual inspection. To get an exact measurement, a profilometer must be used. An exact measurement is not required to determine cylinder condition.

• Check the condition of the snubber. The snubber is located at the closed end of the cylinder. The snubber slows the speed of the cylinder at the end of stroke. Check for cracks, mushrooming, or deformation of the snubber. The fit between the snubber and the cylinder bore is precise. Be sure the mating surface on the piston and the snubber bore mate together smoothly. Using a spotlight may be necessary to see the end of the cylinder where the snubber bore is located. If the snubber is damaged in any way that would prevent the snubber from functioning properly, the cylinder eye casting must be repaired or replaced.

• Refer to Special Instruction, SEBF8072, "Inspection and Salvage of Hydraulic Cylinder Components" for further information on cylinder inspection and retubing.

Table 4

Seal Selection
Pressure	Piston Seals						Head Seals			Rod Seal
	0-20 600 kPa (0-3000 psi)			Over 20 600 kPa (3000 psi)			All Pressures
Maximum Bore Size	Std	0.25 mm (0.010 inch) o/s	0.76 mm (0.030 inch) o/s	Std	0.25 mm (0.010 inch) o/s	0.76 mm (0.030 inch) o/s	Std.	0.25 mm (0.010 inch) o/s	0.76 mm (0.030 inch) o/s
Threaded Gland	Std	Std.	0.76 mm (0.030 inch)	Std.(1)	Std.	0.76 mm (0.030 inch)	O-ring & backup	O-ring & backup	O-ring & backup	Std.
Threaded Crown	Std	Std.	0.76 mm (0.030 inch)	(1)	(1)	(1)	O-ring & backup	O-ring & backup	Oval Seal	Std.
Bolted	Std	Std.	0.76 mm (0.030 inch)	Std	Std.	0.76 mm (0.030 inch)	O-ring & backup(2)	O-ring & backup(2)	Face O-ring seal	Std.

(1)	Threaded crown cylinders are not used in applications with pressures in excess of 20 600 kPa (3000 psi).
(2)	Excavator cylinders use an oval head seal in addition to the O-ring and the backup ring.

Oversized Honing

Current advances in cylinder seal technology the salvaging of cylinder assemblies by oversized honing possible. Usual bore refinishing (glaze removal) increases the ID (inside diameter) of the cylinder assembly less than 0.030 mm (0.001 inch). Oversized honing increases the bore size 0.25 to 0.76 mm (0.010 to 0.030 inch) oversize.

Cylinders that are honed and the inside diameter is not greater than 0.25 mm (0.010 inch) over nominal size, can be resealed using standard bore size seals, regardless of operating pressure. Any bore oversized past 0.25 mm (0.010 inch) using standard seals may cause seal extrusion.

Cylinders that operate at pressures up to 20 700 kPa (3000 psi) can be honed to 0.76 mm (0.030 inch) oversize and resealed using 0.76 mm (0.030 inch) oversize seals. For cylinders bored 0.76 to 1 mm (0.030 to 0.040 inch) oversized, the 0.76 mm (0.030 inch) oversized seals can be used. Any bore oversized past 1 mm (0.040 inch) using 0.76 mm (0.030 inch) oversize seals may cause seal extrusion.

Cylinders that operate over 20 700 kPa (3000 psi) are not recommended for oversize honing.

Depending on the operating pressure, if the bore scratches cannot be removed by honing 0.76 mm (0.030 inch) oversize, the cylinder must be salvaged by retubing. Refer to Table 4 to aid in selecting the correct seal.

Before honing a cylinder assembly oversize, check the availability of oversize seals for the cylinder being repaired. See the latest seal kit IRM (Information Release Memo), PSK (Parts Sales Kit), or the Hydraulic Cylinder & Seal Catalog, PEKP1020.

Honing Equipment

Caterpillar honing equipment for hydraulic cylinder bore refinishing can be classified into three main types: manual, manual hone upgrade, and semi-automatic hones. Caterpillar does not offer a fully automatic hone or a production hone.

Manual Hone

• Is stroked manually.

• Uses manually expanded honing head.

• Is powered by a portable drill motor.

Dealer Service Tools (DST) offers the 9U-6463 Manual Hone. Manual honing tooling is described in the Tool Operating Manual, SEHS9538, "Using the 9U6463 Hone Group and Attachments", which includes a drill, a support stand, a barrel cradle stand, a honing oil tank, honing head, drill motors, and shaft extensions. Honing consumables, such as stones and honing oil, are available separately from DST.

Manual honing equipment is most effective when the job requires removal of light scratches 0.025 mm (0.001 inch) and cylinder glazing. Manual honing is not recommended for removal of large amounts of material. Manual honing tools can be used to hone oversized dimensions, but technician fatigue and available time inhibit this type of activity. Manual honing takes considerably longer to hone a cylinder and to remove large amounts of material.

Manual hones require consistent monitoring of the process by the operator. Manual honing requires the operator to expand the stones manually and considerable physical effort to manually stroke the hone.

Manual Hone Upgrade

• Uses manually expanded hone head.

• Has powered system for honing head, rotation, and stroke.

Caterpillar no longer offers the 1U-9001 and 1U-9002 Automatic Tooling upgrade. The tooling is described in the Tool Operating Manual, NEHS0627, "1U-9001 and 1U9002 Automatic Hone Tooling". Manual hone upgrades are moderate production tools and should be used when moderate quantities of cylinders require work. A manual hone upgrade has automatic feed, which requires an operator to be present at all times to expand the hone head manually.

Note: The information on the 1U-9001 and 1U-9002 Automatic Tooling is retained in this document to support those dealers who still use this tooling.

Manual hone upgrades are effective when cylinder glazing and light to moderate scratches need to be removed. The hone can be used more efficiently than a manual hone because there is not as much reliance on physical labor.

Semi-Automatic Hone - CE Compliant

• Uses an automatically expanded honing head.

• Has powered systems for hone head stroking and hone head rotation.

Illustration 4	g01178541
233-2225 Semi-automatic Hone

The 233-2225 Semi-automatic Hone is no longer available from Dealer Service Tools (DST). The tooling is described in the Tool Operating Manual, NEHS0901, "233-2225 Automatic Hydraulic Cylinder Hone".

Note: The information on the 233-2225 Semi-automatic Hone is retained in this document to support those dealers who still use this tooling.

Once the machine is set, the hone will run until the cycle is complete.

Some features that are on the 233-2225 Semi-automatic Hone include:

• A variable-speed hydraulic-powered carriage to stroke the honing head.

• A hydraulic power pack.

• A load sensing system that automatically expands the honing stones as the stones wear.

• A control panel with a timer for automatic operation.

• More safety shields and switches for safer machine operation.

The semi-automatic hone is fully capable of removing moderate amounts of material in a timely manner. The semi-automatic hone has the capability of removing up to 0.25 mm (0.010 inch) in a reasonable amount of time depending on the size of the cylinder bore.

Semi-automatic hones are essentially the same as a manual hone upgrade. The main difference is the semi-automatic hone uses electronic load sensors to monitor the load from the hone head. The semi-automatic hones automatically expands the stones to keep a consistent load on the stones. A semi-automatic hone will operate continuously expanding the stones until stopped by the operator or until the cycle times out. The operator will usually set the control timer. The hone will automatically stop at the open end of the cylinder at the end of the timed cycle.

Catepillar now offers two hones made by Sunnen Products Company. These two models are the HTA-2100 hone and HTA-4100 hone. Refer to the Sunnen Products Company website for information on the setup and operation of these two hones.

Other Honing Equipment

In addition to a supply of rough and finish stones, various holders, guides, stone/guard supports, and shaft extensions are needed. A bore gauge or an inside micrometer is necessary to measure the cylinder bore.

For large cylinders, if the bore of the cylinder is larger than or equal to the length of the stone used on the honing head, use a longer stone set (a double stone/guide holder). When using a double stone holder, two sets of stones and guides will need to be used. Use the double stone holder to prevent the honing head from cocking sideways in the cylinder and causing inconsistent or out of round cylinder bores.

Marking the stones, guides, and holder is critical when using two sets of stones on a double stone holder. Number all components "1" through "8" so the components can be put back in the exact locations for use later on a different cylinder. The stones will wear on a slight angle, therefore, the stones must be put back in the same position. This wear is normal.

Illustration 5	g01178550
Double stone holder

Honing Operations

Surface Finish

The final surface on the cylinder wall is important. The surface of the cylinder bore must not be too smooth nor too rough. If the bore is too smooth, the lubricating layer of oil between the piston seal and the cylinder wall will be too thin. If the bore is too smooth, the lubricating layer may not even exist. The piston seal may overheat due to excessive friction, may momentarily stick to the cylinder wall, or may cause a high pitched noise.

Bores that are too rough will cause the seal to be ground or cut. A cut seal causes small passages to be created across the face of the piston seal. Hydraulic pressure then forces fluid past the seal. The cylinder will drift and give slow response time.

A surface finish of 0.10 to 0.40 µm (4 to 16 microinches) is necessary for proper sealing and cylinder performance. Surfaces rougher than 0.40 micron may cause seal wear and leakage on some seal designs.. A profilometer is the most accurate method to measure surface finish.

Multiple measurements should be taken. The measurement values should be consistent. If the measurement values vary by a large amount, the cylinder has not reached a consistent surface finish and more honing is necessary.

If the cylinder is put back into service with an incorrect surface finish, the effects may not be immediately detected. A cylinder that is a little too rough or too smooth may pass the pressure test, but the seal life will be reduced. Earlier seal replacement may be required than if the cylinder bore had been honed to the proper surface finish when new seals were installed.

Crosshatch

The hone must be stroked along the length of the bore to finish the inside diameter uniformly. The feed rate in and the feed rate out should take the same amount of time. Varying stroke times will cause accelerated and uneven stone and guide wear. A stroke speed that is too slow will cause the stones to wear more in one area than in another and cause inconsistent bore sizes. Localized honing should be avoided unless the intent is to enlarge a tight (undersized) area.

A proper feed rate will produce a crosshatch pattern. The diagonal scratches of the pattern will be formed at an included angle of 105 to 125 degrees as viewed from the open cylinder end. The crosshatch pattern is determined by a combination of spindle speed and feed rate. In general, a larger bore requires both slower speed and feed. A smaller bore requires a faster speed and feed.

Illustration 6	g01271011
Crosshatch Patterns (A) Not enough crosshatch (B) Too much crosshatch (C) Correct amount of crosshatch

Spindle Speed

The hone must operate at a specific rpm for the stones to cut properly, not wear too quickly, or load with metal particles. In general, the larger the cylinder diameter, the slower the spindle speed. Use the following formula for quick reference to determine an approximate spindle speed.

For all Caterpillar manual and semi-automatic hone systems divide the bore size in millimeters into 20,000 (or the bore size in inches into 800). Example: 20,000 ÷ 101.6 mm (bore) = 197 rpm (800 ÷ 4.00 inches (bore) = 200 rpm. The following spindle speeds are a guideline to get started. These are only starting speeds. Adjust the speeds as needed to control on squeaking, chattering, or stone glazing.

• 320-250 rpm for 64-101 mm (2.5-4 inch) cylinders

• 250-130 rpm for 101-152 mm (4-6 inch) cylinders

• 130-80 rpm for 152-254 mm (6-10 inch) cylinders

• 80 rpm for cylinders over 254 mm (10 inch)

If chattering occurs, check the condition of the stones and wipers. Second, reduce the spindle speed and increase the feed rate. Third, decrease the stone tension.

Feed Rate

The hone must be stroked the full length of the bore to refinish the inside diameter of the cylinder uniformly. The correct stroke speed is important to achieve the correct surface finish. The feed rate must work with the spindle speed to produce the correct finish. The following feed rates are a guideline to get started. These are only starting speeds. Adjust speeds as needed to control on squeaking, chattering, or stone glazing.

• 5-6 cm per second (10-12 feet per minute) for 64-152 mm (2.5-6 inch)

• 4-5 cm per second (8-10 feet per minute) for 152-254 mm (6-10 inch)

• 3 cm per second (6 feet per minute) for cylinders over 254 mm (10 inch)

This starting feed rate is recommended. From the starting feed rate you can stroke faster for a long cylinder and slower for a short cylinder. This speed will allow the stones to wear evenly. A feed rate that is too slow will cause stones to wear more in one area than another and cause inconsistent bore sizes. Localized honing should be avoided unless the intent is to enlarge a tight fit (undersized area). In general, a large bore requires slower spindle speed and a slower feed rate. A smaller bore can handle a higher feed rate and higher rpm.

If chattering occurs, check the condition of the stones and wipers. Second, reduce the spindle speed and increase feed rate. Third, decrease the stone tension.

If stones wear rapidly, reduce the feed rate or use harder stones.

Use care at both ends of the strokes. The stones should not extend more than 25.4 mm (1 inch) past the open end of the cylinder. Do not allow the stones to contact the closed end of the cylinder or damage to the stones may result. Manually push the hone head into the cylinder. When the head contacts the end of the cylinder, pull back 25.4 mm (1 inch) and place the "Left Limit" switch against the hone head at this location.

Illustration 7	g01178813
Do not allow the hone head to extend more than 25.4 mm (1 inch) past the end of the cylinder.

Stone Pressure

Stone pressure exerted on the cylinder wall is also important. If the bore is rough, the pressure should be set low. The low pressure will prevent stone damage. When stock removal is occurring, the stone pressure against the surface of the cylinder can be high. The high pressure will allow for the most efficient stock removal. Too high stone pressure can damage the stones. Parts of the stone can break off.

When the final surface is being placed on the cylinder wall, the pressure should be low. This low pressure will provide the best final surface finish for the cylinder. If stone pressure is too low, the stone can glaze. The stone pressure needs to be high enough to peel back the flat stone granules to expose new sharp granules underneath. If stone glazing occurs, 9U-6748 Dressing Stone can be used to resurface the hone stone.

Note: Cylinder hones use different types of readouts to measure stone pressure. Hones typically use an amp gauge or a pressure gauge. For complete instructions, consult the Tool Operators Manual for your specific hone.

Hone Time

Predicting the exact amount of time to hone a cylinder is difficult. There are many variables to consider. If a cylinder is glazed (too smooth) and has no scratches, the hone time is easier to predict. With proper stone pressure, a proper surface finish can be achieved in a short amount of time. Using a 150 grit stone first then a 400 grit stone is recommended. Use the following times as a starting point for the 150 grit stone.

• 62.5-127 mm (2.5-5 inch) run for 5 minutes

• 127-178 mm (5-7 inch) run for 7 minutes

• 178-254 mm (7-10 inch) run for 10 minutes

• 254-381 mm (10-15 inch) run for 15 minutes

Following the 150 grit stone, use the 400 grit stone for the following times.

• 62.5-127 mm (2.5-5 inch) run for 1 minute

• 127-178 mm (5-7 inch) run for 2 minutes

• 178-254 mm (7-10 inch) run for 3 minutes

• 254-381 mm (10-15 inch) run for 4 minutes

Stone Selection

Proper stone selection is critical to achieve the proper material removal rate and the proper surface finish. Refer to the chart below for recommended stone use. Use the lowest number grit (most course stone) when there is a large amount of material to be removed. Use the middle grit stone when there is moderate material to be removed. Use the fine stones last to achieve the final surface finish.

For deep scratches or pitting from .05 mm (.002 inch) to .13 mm (.005 inch) deep, use the 80 grit stone. For lighter scratches from .025 mm (.001 inch) to .05 mm (.002 inch) deep, use the 150 grit stones. Use the 400 grit stones only after all cylinder bore imperfections are removed.

Note: Remember a 0.13 mm (.005 inch) deep scratch will result in a 0.25 mm (.010 inch) oversize bore. Refer to the "Oversized Honing" section in this document.

Refer to charts below for further information on stone selection and part numbers.

Table 5

Stone Selection, Master Holder, and Stone Support by Bore Diameter
Bore mm (inch)	Cat Part Number	Sunnen Part Number	Stone Grit	Master Holder Cat Part Number (Sunnen Part Number)	Stone Support Cat Part Number (Sunnen Part Number)	Potential Surface Finish micrometer (microinch)
64-69 (2.5-2.7)	208-3596	G25-A25	80 (rough)	None	None	1.905 (75)
	9U-6746	G25-A45	150 (rough)			.890 (35)
	6V-7866	G25-J87	400 (finish)			.178 (7)
69-104 (2.7-4.1)	207-7595	M27-A25	80 (rough)	None	None	1.905 (75)
	9U-6483	M27-A45	150 (rough)			.890 (35)
	6V-7865	M27-J87	400 (finish)			.178 (7)
89-140 (3.5-5.5)	207-7598	N37-A25	80 (rough)	None	None	1.905 (75)
	9U-6480	N37-A45	150 (rough)			.890 (35)
	9U-6481	N37-J87	400 (finish)			.178 (7)
119-178 (4.7-7.0)	207-7597	W47-A25	80 (rough)	9U-6471 (AN355)	None	1.905 (75)
	9U-6479	W47-A45	150 (rough)			.890 (35)
	9U-6478	W47-J87	400 (finish)			.178 (7)
152-229 (6.0-9.0)	207-7597	W47-A25	80 (rough)	246-6040 (AN865)	9U-6473 (AN260)	1.905 (75)
	9U-6479	W47-A45	150 (rough)			.890 (35)
	9U-6478	W47-J87	400 (finish)			.178 (7)
203-305 (8.0-12.0)	207-7597	W47-A25	80 (rough)	9U-6749 (AN875)	9U-6475 (AN280)	1.905 (75)
	9U-6479	W47-A45	150 (rough)			.890 (35)
	9U-6478	W47-J87	400 (finish)			.178 (7)
279-381 (11.0-15.0)	207-7597	W47-A25	80 (rough)	246-6041 (AN885)	246-6193 (AN290)	1.905 (75)
	9U-6479	W47-A45	150 (rough)			.890 (35)
	9U-6478	W47-J87	400 (finish)			.178 (7)

Note: All the bore diameter ranges overlap. If the hone is not already set up from a previous cylinder, choose the largest bore diameter range tooling. Use the stone support if there is an option. Use the double stone holders if there is an option.

Note: For all 400 grit finish stones, a surface finish of 0.178 µm (7 microinches) is achievable. A surface finish of 0.10 - 0.40 µm (4 - 16 microinches) is ideal. This surface finish can be achieved by adjusting the hone finish time.

Table 6

Sunnen Stone
Part Number Example
N3-7A45
N37	A	4	5
-	-	-	-
Series	Abrasive Type	Grit Size	Hardness

Table 7

Grit Size
1-70	5-220	9-500
2-80	6-280	0-600
3-100	7-320	00-1200
4-150	8-400

Table 8

Abrasive Types
A	Aluminum Oxide (for general-purpose roughing and fast stock removal)
J	Silicon Carbide (for fine finishing)
DM, DR, DV	Diamond
NM, NR, NV	CBN Borazon

Table 9

Hardness
1- Soft	9-
3-	11-
5-	13-
7-	15- Hard

Note: Micrometer (µm) or microinch are the units of measurement for the surface finish placed on a cylinder wall. If the honing stones, speeds, and feeds given in this guideline are used, the surface finish shown can be achieved. To check the surface finish of the cylinder tube, use a profilometer.

Caterpillar offers tooling for the honing of a tube that contains a key way. Use double wide stones sets to bridge across the key way. Double wide stones will not become lodged as the stones travel over the keyway. Using double wide stone sets allows the Caterpillar cylinder hone to be a more versatile and useful machine.

Illustration 8	g01178843
Stones for honing a tube with a keyway.

Stones and guides need to be kept as a set. Keep the stones and guides together so all the parts wear evenly to produce a quality final product. Keeping as a set will also help with stone and guide life. Now all the stones and guides will provide equal pressure and cutting force on the cylinder wall. Marking the stones, guides, and holders when using two sets of stones on a double stone holder is critical.

Number all components "1" through "8" so the components can be put back in the exact locations. This step is important if the components are later used on a different cylinder. The stones will wear on a slight angle, therefore the components must be put back in the same position. This wear is normal.

Note: Uneven stone wear may occur that is not preventable. The drive u-joint may cause the head to tilt slightly and cause uneven wear to the stones and guides. A worn out U-joint will maximize this problem.

Illustrations 9 and 10 should be used as a guide to show when a stone and guide need to be replaced.

Illustration 9	g01178847
Worn Guide vs. New Guide

Illustration 10	g01178846
Damaged/worn stone vs. New stone.

The stone on the left is worn. The stone was not used in ideal conditions. The stone pressure could have been lowered to prevent the stone from breaking down. Also, the oil supply should be filtered to prevent other metal particles from entering the cylinder when honing is being completed.

Honing Oil

Honing oil is specially formulated to perform in the demanding conditions set fourth by the hydraulic cylinder honing. Some reasons for using proper honing oil include:

• Minimize galling and chatter.

• Provide lubrication to stones and guides.

• Extend the life of the hone tooling.

• Reduce operating costs.

• Increase the quality of the finished product by cooling and carrying away the honing process residue as intended.

Do not dilute the honing oil. Do not use lubricating oil, cutting oil, or water-soluble oil. Consistent results cannot be expected unless the recommended full strength honing oil is used. Use of the wrong oil or not enough oil volume can cause steel to embed in the stone. When embedding happens, the stone is bad and should be replaced.

9U-6484 Honing Oil, with the proper formulation and viscosity, is available from Dealer Service Tools in 18.9 L (5 US gal) containers. 9U-6484 Honing Oil is formulated for honing steel hydraulic cylinder tubes.

Manually run the hone oil into the cylinder, as shown in the Tool Operating Manual. Perform this action until oil is flowing out of the open end of the cylinder into the top of the hone oil tank. Observe the diameter of hone oil as the oil falls from the cylinder. To start out with, the diameter of the hone oil stream should be about the size of a pencil or slightly larger, approximately 8-10 mm (0.31-0.39 inch). The hone oil flow should be enough to allow proper lubrication and chip removal. However, too much flow can contribute to an excessive amount of oil to be thrown off the hone head and out of the open end of the cylinder.

Note: The main ingredient in the honing oil is animal fat, which may solidify at cold temperatures. This solidification will not harm the system and the oil will dissolve once the honing oil is warm.

Do not use 5P-8615 Honing Oil when honing steel hydraulic components. 5P-8615 Honing Oil is formulated for honing cast iron parts.

Oil should be filtered before pumping into the hone head. Contaminated oil is a large reason for poor hone performance. If the honing oil is contaminated, the oil will introduce more unwanted, abrasive particles into the honing system. These particles can cause scratches and gouges in the cylinder tube surface. The particles can become lodged between the stone or holder and the cylinder bore. A scratch can occur as the particles travel around with the hone head.

One reason customers do not purchase the correct oil is the cost. In the end, the cost of oil is less than 0.1% of the total honing process. Use the correct oil to increase the life of the hone tooling. The correct honing oil decreases the time and labor that is needed to complete the honing process.

The Caterpillar hone oil tank incorporates a roll of filter media that should be rolled to expose clean filter media every few cylinders. Once the entire roll of filter media is used, inspect and possibly change the hone oil. Check for sludge at the bottom of the tank. Use a piece of wood or steel as a dipstick to check for solids at the bottom of the tank. If necessary, completely drain and clean the tank. Fill the tank with new hone oil.

Cleaning

The honing process creates a large quantity of abrasive particles that must be cleaned from the cylinder before the cylinder is resealed. The abrasives are either stone particles, the binder used to hold the stone particles together, guide material, or metal shavings from the cylinder bore. Abrasives can cause accelerated wear to hydraulic cylinder seals and other components in the hydraulic system if not properly removed from the cylinder bore.

After honing, allow the honing oil to drain from the cylinder assembly. Properly wash the cylinder assembly inside diameter using the 250-6597 Cylinder Washer available from Dealer Service Tools, or equivalent. Reference the Tool Operating Manual, NEHS0927, "Procedures for Using the 250-6597 Cylinder Washer Tank Group" for operating and repair instructions.

Illustration 11	g01179117
250-6597 Cylinder Washer

The cylinder washer is used to:

• Clean honing oil and metal particles from inside reconditioned cylinders (provides quick and efficient cleaning method).

• Cleans cylinders ranging from 101 to 343 mm (4.0 to 13.5 inch) diameter and 1.9 to 3.6 m (6 to 12 ft) in length.

• Unit can be positioned at end of manual or semi-automatic hone group (allows cylinders to remain clamped in hone group during cleaning process).

• Washer uses an air-powered drill to rotate cleaning brushes while a pump supplies cleaning solvent to the brush head.

• Uses a disposable bag filter to capture contaminants (keeps wash solvent clean as well as making cleanup and disposal much easier).

• Unit is shipped with 110-volt capability, but can easily be converted to 220-volts (no additional parts are required for the conversion).

Hydrosolv 4165, a soap product available from the Dealer Service Tools, is suited for parts cleaning applications. Hydrosolv 4165 contains agents that provide rust protection for up to two days, and is available in 18.95 L (5.000 US gal)( 1U-5490 Cleaner/Degreaser which replaced the following canceled item: 185-4619 Cleaner/Degreaser EAME).

After the cylinder is washed, elevate the capped end of the cylinder to allow the cylinder to drain. Allow approximately 10 minutes.

If the cylinder will not be assembled for several weeks, coat all exposed metal surfaces with clean hydraulic oil. All openings must be capped and plugged. If the cylinder tube will not be assembled for up to a year, 4C-6794 V.C.I. Oil should be used. Refer to Special Instruction, SEHS9031, "Storage Procedure for Caterpillar Products" for general storage recommendations.

The storage times given are approximate. Ambient temperature and humidity level will greatly affect the storage time. Both types of oil can be applied with a spray wand. The wand should be long enough to reach the bottom of the cylinder. The tube opening must have a protective covering after the oil is applied.

Honing Economics

Hydraulic cylinder honing can be an excellent process to gain a second or third service life from a hydraulic cylinder. However, if the cylinder tube is beyond repair, the best alternative may be to purchase a remanufactured cylinder or to retube the cylinder. This decision must take into account the size and cost of the cylinder, estimated honing time, labor rate, and required turn around time.

Since the hone heads on a manual hone and semi-automatic hone are the same, a manual hone should be able to correct any imperfections in the cylinder. However, the amount of pressure that can be applied with the manual hone is much less than the semi-automatic hone. Less pressure lessens the rate of stock removal, and increases the honing time and repair cost when using a manual hone. Use the following equations to get an approximate honing time. This time can then be used to estimate the amount of labor that must be put in to the cylinder for the rebuild.

Manual Hone Time Equation

This equation should be used to estimate the operation time while using a manual hone. The equation does not take into account operator breaks or the different operators ability to physically stroke the hone. To get a more consistent honing time, a remote hydraulic feed power unit hone should be used. The following equations should be used to determine the actual honing time required to remove the stock on a cylinder.

• Millimeters:

Length x Diameter x Required Stock Removal x 0.00076 = Honing Time in Minutes

Example: 1220 mm x 101.6 mm x 0.254 mm x 0.00076 = 24 Minutes Honing Time

• Inches:

Length x Diameter x Required Stock Removal x 12.5 = Honing Time in Minutes

Example: 48" x 4" x 0.010" x 12.5 = 24 Minutes Honing Time

Semi-Automatic Hone Time Equation

This method of estimating cycle time is most accurate when using the Caterpillar semi-automatic hydraulic cylinder hone, part number 223-2225. This equation gives the actual time that the hone needs to operate, and does not take into account setup and preparation time.

Honing Time Equation

• Millimeters:

Length x Diameter x Required Stock Removal x 0.0003 = Honing Time in Minutes

Example: 1200 mm x 100 mm x 0.28 mm x 0.0003 = 10 Minutes Honing Time

• Inches:

Length x Diameter x Required Stock Removal x 5 = Honing Time in Minutes

Example: 48" x 4" x 0.010" x 5 = 10 Minutes Honing Time

Stone Life

Another important factor, essential for efficient honing, is estimating the number of work pieces that can be completed with a set of stones. This number is important when calculating the cost of honing and will ensure that enough stones are available to complete the job.

• Millimeters:

(Final Diameter²-Starting Diameter²) x Length x 0.00000183 = Sets of Stones Per Job

Example: (101.6² mm-101.35² mm) x 1219 x .00000183 = 0.11 Sets of Stones Per Job

1.0 set of stones ÷ 0.11 = 9 Parts Per Stone Set

• Inches:

(Final Diameter²-Starting Diameter²) x Length x 0.03 = Sets of Stones Per Job

Example: (4.0"²-3.990"²) x 48" x 0.03 =0 .11 Sets of Stones Per Job

1.0 set of stones ÷ 0.11 = 9 Parts Per Stone Set

Manual Honing Procedure

For additional information on manual honing, refer to, Tool Operating Manual, SEHS9538, "Using the 9U-6463 Hone Group and Attachments".

1. Clean all grease, hydraulic oil, and dirt from the cylinder assembly before the cylinder assembly is loaded on the hone. This cleaning will prevent contaminating the honing oil.

2. Place the honing head in the end of the cylinder assembly.

3. Set travel stop for rear carriage movement so the stones do not extend more than 25.4 cm (1.0 inch) past the end of the cylinder assembly. When possible, set a travel stop for forward carriage movement so the stones do not contact the closed end of the cylinder assembly.

4. Expand the stones in the bore by turning the hand wheel counterclockwise (viewed from behind the drill motor) until the stones contact the bore. Check to see that the stones are tight against the bore and that the guides are loose. If the guides are not loose, file up to 1.00 mm (0.039 inch) from each guide to relieve guide pressure and speed up stock removal. Turn the hand wheel 1/4 to 1/2 turn clockwise.

5. Start the honing oil supply pump.

6. After a stream of oil flows from the cylinder assembly, start the hone rotating in a clockwise direction (viewed from behind the drill motor).

7. Slowly stroke the hone into and out of the bore. Be alert for changes in the bore diameter. The diameter may vary along the length of the bore due to damage or different amounts of wear throughout the cylinder.

8. Initially, the stones will be loose in the bore causing the stones to rattle. To expand the stones, apply a slight stopping pressure to the hand wheel (or turn the hand wheel counterclockwise) while the hone is rotating.

9. Increase the stroke speed to 76 to 102 mm per second (3 to 4 inches per second).

10. As the bore gets larger and the stones wear, the stones will begin to rattle again. The head will become loose inside the bore. Expand the stones by turning the hand wheel counter clockwise. Overly aggressive expansion of the stones may cause the stones to grab and result in a broken stone and/or drive mechanism. The stones will be cutting efficiently when considerable force strokes the hone at a rate of approximately 76 to 102 mm per second (3 to 4 inches per second). When honing, the time to stroke in and to stroke out should be the same. Varying stroke times will cause accelerated and uneven stone and guide wear.

11. If tight spots are felt during stroking, dwell at those areas until the bore becomes larger. Do not dwell at either end of the stroke unless the intent is to enlarge a tight spot at the end. Gradually lengthen the stroke as the bore becomes straighter. To prevent excessive heat buildup, do not hone in one area for an extended period.

12. Stop honing at regular intervals to inspect the bore and determine if all damage to the bore has been removed. To avoid creating unnecessary, longitudinal bore scratches, plan to stop honing so that the honing head is at the open end of the cylinder assembly on the outward stroke.

13. When the roughing stones have removed all damage and reconditioned the complete length of the bore, switch to finishing stones.

14. Use the finishing stones and hone the complete length of the bore to get a surface finish of 0.10 to 0.40 µm (4 to 16 microinches).

15. Allow the honing oil to drain from the cylinder.

16. Clean the cylinder assembly as described in the "Honing Operations" section of this guideline.

Note: For detailed instruction, refer to the Tool Operating Manual, SEHS9538, "Using the 9U6463 Hone Group and Attachments" for the manual hone.

Honing Procedure for Manual Hone Upgrade

Note: This description is just an overview of the manual hone upgrade setup and operation. For complete detailed instructions and pictures, see Caterpillar Tool Operating Manual, NEHS0627, "1U-9001 and 1U-9002 Automatic Hone Tooling".

1. Clean all grease, hydraulic oil, dirt, and so on, from the cylinder assembly before the cylinder assembly is loaded on the hone. This cleaning will prevent contaminating the honing oil.

2. Jog the work piece carriage forward and place the honing head in the end of the cylinder assembly.

3. Expand the stones inside the bore by turning the hand wheel counterclockwise (viewed from behind the rotation motor) until the stones lightly contact the bore. Back off the hand wheel with a 1/4 to 1/2 turn clockwise.

4. Set the rear stop for the stroke limit switch so that no more than 25.4 mm (1 inch) of the stones extend from the end of the cylinder assembly. Jog the carriage forward to bottom the hone head gently against the cylinder end cap. Then, back the hone head away approximately 2.5 mm (0.10 inch). Set and lock the forward stop for the stroke limit switch.

5. Retract the work piece carriage to the rear stop.

6. Ensure all of the guards and shields are in place.

7. Start the honing oil supply pump. Adjust the flow so that a pencil-sized stream of oil drains from the end of the cylinder assembly.

8. Start the hone rotating in a clockwise direction (viewed from behind the rotation motor).

9. Start the feed system and slowly stroke the hone in to and out of the bore. Be alert for damage or changes in the bore diameter. The diameter will vary along the length of the bore due to different amounts of wear.

10. If the stones are not cutting, apply light stopping pressure to the hand wheel to expand the honing head. Use caution when expanding the stones, the stones may grab and transmit excessive torque back through the drive shaft into the rotation motor. Repeat the procedure as the bore gets larger and the stones wear.

11. If tight spots are noticed during stroking, manually activate the limit switches to cause the hone to dwell at those areas. As the bore gets larger in tight areas, gradually lengthen the stroke. Do not hone in one area for an extended period to prevent excessive heat buildup.

12. Stop honing at regular intervals. Measure and inspect the bore to see if all the damage has been removed. To avoid creating unnecessary, longitudinal scratches, continue to feed the hone while the head is rotating. Plan to stop honing last stroke of the hone, so that the head is at the open end of the cylinder assembly.

13. When honing is complete, final honing with finish stones will add approximately 0.025 mm (0.001 inch). This issue must be considered when approaching the 0.25 mm and 0.76 mm (0.010 inch and 0.030 inch) over size restrictions.

14. Hone the complete length of the bore to get a surface finish of 0.10 to 0.40 µm (4 to 16 microinches).

15. Allow the honing oil to drain from the cylinder assembly.

16. Clean the cylinder assembly as described in the cylinder cleaning section of this guideline.

Semi-Automatic Honing Procedure

Note: This description is just an overview of the hone setup and operation. For complete detailed instructions and pictures, see Caterpillar Tool Operating Manual, NEHS0901, "223-2225 Automatic Hydraulic Cylinder Hone".

1. Clean all grease, hydraulic oil, dirt, and so on, from the cylinder assembly before the cylinder assembly is loaded on the hone. This cleaning will prevent contaminating the honing oil. Be sure that the cylinder is tipped forward to allow the honing oil to drain out of the tube. Securely fasten the cylinder in the V block with the provided ratchet style straps.

2. Rotate and pull out the two "Emergency Stop" switches located on the operator control stand and in the front of the hone.

3. Press the "Power Control" button on.

4. From the "Main Menu Screen":

   • Turn the "Dwell Timer ON" or "OFF".

   • Turn the "Stone Tension" switch "ON" or "OFF".

   • Set the dwell time.

   • Press the "Master Control Screen" touch pad.

5. Select the bore size of the cylinder on the "Master Control Screen". The selected bore will be highlighted in green.

6. Select the appropriate surface texture. The switch will toggle between "Rough and Finish".

7. Set the cycle time by touching the "Set Hone Timer" touch pad.

8. Press the "Setup" touch pad and follow the directions given in the message boxes. After each step is complete, press the "Next" touch pad.

9. Assemble the hone head tooling. Refer to Tool Operating Manual, NEHS0901, "233-2225 Automatic Hydraulic Cylinder Hone" page 7, tooling set up, for detailed instructions. Carefully push the head into the cylinder until the stones stick out of the cylinder 25.4 mm (1.0 inch).
   Show/hide table

   Illustration 12	g01179326
   Arrows indicate how far hone head should protrude from the cylinder tube before reversing direction. "Right Limit" switch should be set to this point.

10. Slide the "Right Limit" switch against the hone head until the limit switch is activated and the "Right Cylinder" stop screen light is on.

    Note: The set screw that is attached to the carriage and activates the limit switch should be adjusted for maximum length. The set screw that is attached to the sliding mechanism that holds the limit switch should not be used at all. The set screw should be adjusted to minimum length or removed completely. Often times, this set screw is incorrectly used as a mechanical stop. The carriage should never hit the set screw. This adjustment applies for both the right and left limit switches.

    Show/hide table

    Illustration 13	g01179328
    "Right Limit" switch in position against the hone head.

11. Loosen the bar knobs and align the hone tooling shaft vertically by moving the hone head up or down. The shaft should be level or on a decline as the shaft goes from the hydraulic motor to the hone head. This step prevents honing oil from flowing down the shaft, dripping hone oil on the hone bed, and throwing oil on the operator.
    Show/hide table

    Illustration 14	g01179329
    Align hone tooling so shaft is level or on a decline from right to left.

12. Push the hone head inward to the bottom of the cylinder. Then pull head out 25.4 mm (1.0 inch) to allow for travel overrun. Position the "Left Limit" switch against the hone head until the left cylinder stop light comes on. Tighten the stop in place.

13. Turn the feed assembly hand wheel counterclockwise to expand the stones until the stones slightly contact the bore. When the "Stone Tension" touch switch is "ON", the stones will automatically expand.

14. While retracting the hone head out of the cylinder, adjust the hone head diameter with the adjustment hand wheel to the smallest diameter of the cylinder bore. Use the friction of the stones and guides against the cylinder wall to identify any tight spots (undersized bore areas). Tight spots might damage the hone during the initial start-up.

15. From the "Main Menu" screen, touch the "Hone Oil" touch pad and change to auto. This action will start the oil supply.

16. Push the "Hone Rotation Start Button" to begin the automatic honing process. The hone head will not start rotating immediately.
    Show/hide table

    Illustration 15	g01179333
    "Hone Rotation Start Button". Pressing this button will start the hone operation.

17. Set the speed (rpm) of the hone head and the traverse feed using the two control valves on the hydraulic power supply. Turn the knob on the pump control valve counterclockwise to increase the speed and clockwise to decrease the stroking speed.

18. If tight spots are noticed during stroking, manually activate the limit switches to cause the hone to dwell at those areas. As the bore gets larger in tight areas, gradually lengthen the stroke. Do not hone in one area for an extended period to prevent excessive heat buildup.
    Show/hide table

    Illustration 16	g01179336
    Control valves for feed and speed.

19. Stop the hone at regular intervals to measure the new bore size and determine whether all bore damage has been removed. Plan to stop the honing head and stones at the open end of the cylinder. This action avoids scratching the bore as the honing head is withdrawn from the bore.

20. Rotate the hand wheel clockwise until the stones are compressed. Move the right cylinder stop to facilitate honing head removal.

21. If all scratches have been removed, or if the bore is within 0.025 to 0.051 mm (0.001 to 0.002 inch) of the final bore size, no further rough honing is needed.

22. Change to finishing stones and repeat the honing process.

23. Hone the bore with finishing stones until the desired bore size is reached and the surface finish is 0.10 to 0.40 µm (4 to 16 microinches).

Troubleshooting

Note: Items to check include the stones, mandrel, oil, pressure, and speed.

• Stones - be sure that the proper stones are being used. Be sure that the stones are not too hard or too soft and are the proper grit for the application.

• Mandrel - make sure that the Mandrel is of the correct size, alignment, design. The mandrel should be straight and true.

• Oil - Oil should have the correct lubricity and be clean, free of all foreign debris.

• Pressure - be sure that the pressure is set correctly. Make sure that the pressure is not set too high so that the stones are being crushed or too soft so that the stones are loose in the cylinder bore.

• Speed - vary the speed to find the best speed for your particular application.

Also see reference chart for troubleshooting information.

Table 10

Honing Troubleshooting Guide
Condition to be Corrected		Step 1	Step 2	Step 3	Step 4	Step 5
Slow stock removal		Increase the spindle speed	Increase the cutting pressure	Use only 9U-6484 Honing Oil(1)	Use softer stones	Use coarser grit stones
Stones not cutting	Stones are glazed (stone surface looks clean but cutting grains are dulled)	Sharpen A or J stones with a 9U-6748 Dressing Stick	Increase the cutting pressure	Increase the stroking speed	Use softer stones (one with a lower hardness number)	Make sure that 9U-6484 Honing Oil is being used(1)
	Stones are loaded (stone surface looks smeared and clogged with chips)	Clean the stones with a 9U-6748 Dressing Stick.	Increase the stroking speed.	Use softer stones (one with a lower hardness number).	Use coarser grit stones (one with a lower grit number).
Poor stone life		Decrease the cutting pressure	Use a faster spindle speed	Use harder stones (one with a higher hardness number)	Use coarser grit stones (one with a lower grit number)
Chatter		Vary the rpm and stroke rate	Relieve the guides 1.00 mm (0.039 inch)	Reduce the cutting pressure	Switch to guideless stones unless the bore has a keyway or is larger than 203 mm (8.0 inch)
Bell mouth		Decrease the amount of overstroke	Use softer stones	Caution: over-correction of bell mouth will lead to a barrel condition
Barrel		Increase the amount of overstroke. Do not overstroke more than 1/3 the stone length		Use finer grit stones	Caution: over-correction will lead to a bell mouth condition
Taper at the open end of the bore		Short stroke (dwell) at the tight end of the bore
Taper at the closed end of the bore		Provide adequate oil flow at the bottom of the bore to wash out the shavings	Short stroke at the closed end of the bore	If the bore has insufficient or no relief at the bottom of the bore, use a hard-tip stone set	Provide additional relief at the bottom of the bore
Cylinder bore is out-of-round		Ensure that the honing tool is the recommended size for the diameter to be honed		If honing a thin wall part, decrease the cutting pressure	If the stones stop cutting at decreased pressure, use softer stones (one with a lower hardness number)
Surface waviness		Use honing tools with sufficient stone length to bridge waviness (or ports in a bore)
Surface finish is too rough		Decrease the cutting pressure	Use finer grit stones (one with higher grit number)	Use only 9U-6484 Honing Oil(1)
Random scratches in the bore		Decrease the cutting pressure	Use finer grit stones (one with higher grit number)	Use softer stones (one with a lower hardness number)	Use only 9U-6484 Honing Oil(1)

(1)

Many honing problems, such as poor cutting action, poor stone life, and rough finish, are caused by the wrong honing oil, insufficient honing oil, dirty oil, or contaminated honing oil. Use only clean, full-strength, 9U-6484 Honing Oil. Ensure that the oil is not diluted or cut with other oils. Keep solvents and cleaning fluids away from the hone. The information in the chart must be considered general in nature. Contact the machine manufacturer for specific information.

Hydraulic Cylinder Hone Suppliers

Refer to the following for a list of approved suppliers.

Sunnen Products Company
7910 Manchester Road
St. Louis, MO 63143
www.sunnen.com
(314) 781-2100