TM 9-4910-638-14&P
1 - Before inserting micrometer spindle in boring head, clean hole with bristle brush furnished.
2 - Insert the tool holder in the boring head. Turn guard ring on micrometer to the left (to protect tool bit and micrometer),
insert the micrometer spindle in boring head and push it in until it clicks into place.
3 - Turn the tool bit guard ring back to the right, allowing the tool bit point to gently contact the micrometer face. DO NOT
rotate micrometer while tool is in contact with the face; scratches will affect setting size.
4 - Lock the tool holder in place, remove micrometer.
NOTE
For best uniformity of tool setting, use the same part of the mike face in contact with the tool bit
for all settings. This is easily done by keeping the micrometer lockscrew in the same position
each time.
CAUTION
When removing the tool holder from the boring head, have one hand on the tool to prevent its
flying out.
The finishing tool is set in the boring head in exactly the same way, after resetting the micrometer
for the desired finished size.
IMPORTANT
Be sure the setting of the boring machine micrometer corresponds with the inside micrometer used in measuring the
cylinders. If necessary to reset the tool setting micrometer, proceed in the following manner:
First set the boring tool with the tool setting micrometer to take a light cut and lock the knurled thumbscrew to retain the
micrometer setting. Bore about an inch down, then measure the hole with the inside micrometer.
Second, loosen the setscrew in the hub of the thimble of the tool setting mike, the thimble to correspond with the
measured size of the hole, and lock the setscrew.
Third after thus adjusting the micrometer thimble, set the micrometer to a size 5 or 10 thousandths larger, bore again and
recheck.
If further adjustment is necessary, reset the thimble and check again. Repeat the two micrometers read alike.
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