Use Of 6V7898 Dial Bore Gauge Group{0761} Caterpillar

The 6V7898 Dial Bore Gauge Group permits measurements to be taken in diameter ranges of 50.0 to 200.0 mm in increments of 0.002 mm. The gauge has a depth range of 13 to 300 mm. This high degree of accuracy is needed, especially in applications such as the measurement of connecting rod bores.

Components Of 6V7898 Dial Bore Gauge Group

1. Dial Bore Gauge.

2. Storage Box.

3. Gauge Points with Locknuts.

4. Gauge Point Extensions.

5. Hex Wrenches.

6. Indicator Finger Ball Tool.

7. Gauge Point Ball Tool.

8. Wrench.

How To Use The 6V7898 Dial Bore Gauge Group

(1) Find the correct gauge point, using the table below. For example, if the bore to be measured has a diameter of 114 mm, use gauge point no. 7 + 2.

(2) Install the correct gauge point (1) in the dial bore gauge. Carefully put gauge group (2), with gauge point, into the size setting fixture. See Form SMHS8254 for adjustment procedure. Adjust spindle (3) until it reads the exact size being set.

(3) Adjust gauge point (1) until indicator hand (4) is at the 12 o'clock (straight up) position, and counter hand (5) is at "0" position. Use wrench (6) to tighten locking nut (7) to hold gauge point (1) in the adjusted position.

(4) Again put the dial bore gauge into the size setting fixture. To zero the dial indicator, loosen bezel screw (8). Move the indicator back and forth as shown, until the minimum reading is obtained. Reset zero as necessary by turning bezel (9), then tighten bezel screw (8).

(5) Put the dial bore gauge into the bore that is to be measured and work the gauge back and forth to get the minimum measurement. Any reading other than zero, is the amount of deviation, plus (+) or minus (-), from the size for which the gauge was originally set.

Adjustment Of Centralizer Points

(1) For maximum accuracy, the centralizer points must be in firm contact with the wall of the bore being measured.

(2) Put 1.98 mm hex wrench (1) in centralizer stop adjustment (2), and turn the stop adjustment with the wrench to adjust centralizer points (3) so they are firmly in contact with the wall of the bore being checked.

(3) Slide the gauge head IN and OUT of the bore several times to check the adjustment. The more near the centralizer points are set to the actual bore size being checked, the easier it will be to put the gauge into the bore. The centralizer points must always make contact with the sides of the bore.

Adjustment Of Worn Centralizer Points

When the centralizer points (1) become worn, they must be adjusted to keep accuracy. Always adjust both points at the same time. Do this by putting the long leg of 2.38 mm hex wrench (2) through both centralizer points, and turning both points at the same time, until new wear surfaces are in contact with the wall of the bore.

Changing The Position Of The Indicator Housing

(1) If necessary, the indicator housing can be turned up to 90° in relation to the gauge head using the following procedure. Put the 2.38 mm wrench (1) into access hole (A) for the locking screw. Loosen the locking screw 1/2 no more than turn (180°).

(2) Turn the indicator housing to the position desired. Hold indicator housing (2) in one hand and the gauge head in the other, then slide the indicator housing slightly away from the extension sleeve (3). The indicator hand will move to the 9 o'clock position (its maximum counterclockwise position).

NOTE: The revolution counter hand must be at "0" when the indicator hand is at "0".

(3) Slightly twist the indicator housing and extension sleeve assembly from side to side and push (slide) them together until the indicator hand just begins to move clockwise. Now reverse the direction, pulling the indicator housing away from the extension sleeve, until the indicator hand stops between 9 o'clock and 10 o'clock. Use wrench (1) to tighten the indicator locking screw.

Rotation Of Gauge Point Ball

If the gauge point ball becomes flat or worn, rotate (turn) the ball to give it a new contact position, according to the procedure that follows. Put a clean cloth under the gauge point ball during this procedure.

(1) Put gauge point ball tool (1) in position in the slot in gauge point (2), under gauge point ball (3). Put your thumb over the ball and slowly pry up with tool (1) until the ball comes out.

(2) Turn the ball so an unworn part will face out of the gauge point, and use gauge point ball tool (1) to press the ball into the gauge point. Press the gauge point ball against a hard surface to make sure it is fully seated in the gauge point.

Rotation Of Indicator Finger Ball

(1) If indicator ball (1) becomes flat or worn, use indicator finger ball tool (2) to remove the ball so it can be turned to give it a new contact position, according to the procedure that follows. Put a clean cloth under the gauge point ball during this procedure.

(2) Push the blade of ball tool (2) into the slot under ball (1) in the indicator finger which intersects the ball socket. Pry up to remove ball (1). Ball (1) will be held in position in tool (2).

(3) Turn ball (1) in ball tool (2), to change the location of the flat spot.

(4) Push down on centralizer point (3) and insert gauge point ball tool (4) under ball socket (5). This is done to aid in installation of ball (1) and to prevent damage to the gauge when ball (1) is again installed in the ball socket.

(5) Use indicator finger ball tool (2) to install ball (1) in position in ball socket (5), then remove tool (2). Make sure the ball is fully in the socket by pushing firmly against the ball with the back of ball tool (2).

(6) Remove gauge point ball tool (4). Check the calibration of the gauge.

Repair Of The 6V7898 Dial Bore Gauge Group

The dial bore gauge group should be sent to the manufacturer for service. A letter should be with the returned gauge group, giving a description of the problem and the date of purchase from Caterpillar. Gauge groups less than one year old will be repaired under warranty, except for abuse. Cost of out-of-warranty repairs will be charged to the owner. The gauge group should be sent to the following repair center.