Page 280 - Mechanical Engineer's Data Handbook

268 MECHANICAL ENGINEER’S DATA HANDBOOK

7. I .4 Vernier calliper gauge

This is used for internal and external measurement. It
Micrometer head has a long flat scale with a fixed jaw and a sliding jaw,
with a scale, or cursor, sliding along the fixed scale and
read in conjunction with it. Two scales are provided to
allow measurement inside or outside of the jaws.

Large outside miaumeter with extension rod
Part of vernier

Vernier calliper guage
Reading a vernier calliper gauge
Inside micrometer
1-mm and 0.5-mm divisions screwed with a 0.5mm Reading shown:
pitch thread and a ‘thimble’ graduated around its Reading on main scale=43.5 mm
circumference with 5W.01 mm divisions. Reading on cursor = 0.18 mm
An ‘inside micrometer’ has the fixed anvil projecting Total reading = 43.68 mm
from the thimble; extensions may be attached. A
‘micrometer head’ is available consisting of the barrel Main scale
and thimble assembly for use in any precision measur-
ing device.

Reading a micrometer Cursor
1.1.5 Dial test indicator (dial gauge)
Reading shown:
Reading on barrel = 5.5 mm
Reading on thimble = 0.28 mm
Total reading = 5.78 mm

Thimble

The linear movement of a spring-loaded plunger is
magnified by gears and displayed on a dial. Various
sensitivities are available and a smaller scale shows
complete revolutions of the main pointer. A typical
indicator has a scale with 1OO-O.01 mm divisions and a
0.01 -mm divisions small dial reading up to 25 revolutions of the pointer,
Micrometer Le. a total range of 25 mm.