This document discusses screw metrology and measurements. It describes measuring the major diameter, minor diameter, pitch diameter, pitch, included angle, and thread form of screws. Errors in major and minor diameters can cause interference or a reduction in flank contact between mating threads. Methods for inspecting screw threads include ring screw gauges, plug screw gauges, thread caliper gauges, and pitch measuring machines. Ring screw gauges are used to check external threads while plug screw gauges check internal threads.
3. CRESAT
ROOT
MAJOR DIAMETER
MINOR DIIAMETER
PITCH
LEAD
DEAPTH
6. measurements
(i) Major diameter,
(ii) Minor diameter,
(iii) Pitch diameter,
(iv) Pitch,
(v) Included angle,
(vi) Thread form,
(vii) Thread flank angle, etc.
7. Errors in Major and Minor
Diameters
This error is due to improper machine
setting. Errors on major and minor
diameter will cause.
(a) Interference between mating threads,
preventing engagement between mating
bolt and nut.
(b) Reduction in flank contact, if the
error is in the other direction. It may
lead to and excessive weakening of the
threads and too much slackness
between the mating parts
11. Ring Screw Gauge
The Ring screw gauge has similar principle
to a plain ring gauge, except that screw
threads are cut on the inner surface of the
ring screw gauge.
Ring screw gauge in used to check screw
threads on outside of cylindrical objects like
bolts and shafts. They may be Go and
Not-Go types.