CASE & FRAME GP 9W1070 - Caterpillar

A slight amount of wear on a gauge will cause an incorrect measurement and may cause rejection of some reusable pistons. Wear on a gauge is extremely difficult to measure. It is recommended an extra new gauge group be kept as a master set. A procedure should then be established to periodically compare measurements of all gauges in use to the master set. A gauge is worn out and should be discarded if it shows a piston as not reusable and the master gauge shows the piston ring groove as reusable.
As a Keystone piston ring gauge group wears, fewer and fewer pistons will measure reusable. Correct usage of this type of tool can be found in Service Magazine, June 1, 1981, Page 4, "Correct Usage Of Keystone Ring Groove Gauges" and Service Training videotapes, "Use of Piston Ring Groove Gauges", 3/4" U-matic Form SEVV9164 and 1/2" VHS SEVV8164.