Bowers Group XTA Analogue Bore Gauge - Manual (Page 2)

NOMENCLATURE & SETTING INSTRUCTIONS (METRIC)
HOW TO READ...
All metric micrometers are graduated in 0.005mm divisions. The
sleeve has a datum line, and the thimble is graduated as illustrated
below. The sleeve is graduated in 0.5mm divisions and one complete
revolution of the thimble is equal to 0.5mm. To read the instrument,
read the size on the sleeve to obtain the nearest half millimetre and
to obtain hundredths and microns read the number on the thimble
which lines up with the datum line on the sleeve.
An example is illustrated below.
RESETTING PROCEDURE...
Should the gauge start to lose accuracy due to wear etc., it may be
reset as follows :-
1) Insert the instrument into the setting ring gauge and set at the
correct tightness using the ratchet controller.
2) Lock the spindle with the locking screw located through the
hole in the grip-ring.
3) Loosen the ratchet controller by inserting the allen-key provided
into the screw located in the end of the controller and unlock
the screw.
4) The thimble will now be free and can be rotated and set to the
size on the setting ring.
5) Re-tighten the controller screw and slacken off the spindle
locking screw. The micrometer is now reset.
6) Recheck the gauge in the setting ring. Gauge reading should be
the same as the setting ring calibrated value.
A KEY IS PROVIDED TO MAKE ADJUSTMENTS OF THE MICROMETER
NUT IN THE EVENT OF WEAR.
PROCEDURE:–
1) Remove the thimble and spindle assembly from the micrometer
by completely winding the thimble off the sleeve.
2) Locate the key in the slots of the brass nut.
3) Make adjustments in very small increments. A clockwise rotation
of the brass nut will close the nut to compensate for wear.
4) Replace the thimble assembly and recalibrate the gauge as per
resetting procedure above.
In the illustration above the micrometer reading would be
16.015mm.
EXTENSIONS: When extensions are used for deep hole
measurement it will be necessary to reset the instrument as per the
resetting instructions below.
IMPORTANT NOTE : The anvils have a fixed amount of travel. DO
NOT remove anvils from the measuring head.