Sunday, 24 May 2020
MECHANICAL INSTRUMENTS

Types of Thread Gauges

The thread gauges are essential used for measuring screw threads.The types of screw threads are. 

  1. Caliper gauge
  2. Ring screw gauge
  3. Plug screw gauge

Caliper gauge

The caliper gauges are similar to gap gauges with threads provided on anvils. The front anvils with full thread form acts as GO gauge, to check the threads below the size limit.

The screw with exact effective diameter  and pitch errors will not passing through GO anvils, Whereas eliminating pitch error by reduction ineffective diameter enables the screw to pass through GO as well as NO GO anvils. This leads to rejection of screw threads.

Ring screw gauge

The ring screw gauges are used for gauging bolts during production. It is provided with a system of limits to check the dimensions of the part. A thread ring gauge may be used to check the pitch diameter, major diameter, etc.

Ring screw gauge
Ring screw gauge

By using ring gauges, the lead errors of thread can be easily determined. A special precaution must be taken to avoid excessive pressure on gauge, while checking five or more threads.

Plug Screw Gauges

The plug gauges are used for gauging internal threads. It is made to the minimum dimensions of internal threads, to ensure accurate inspection. The different elements of threads such as major diameter, minor diameter, effective diameter, etc., being checked, define the form of thread, angle and pitch.

Generally, NO GO gauge is used is for gauging major, minor and effective diameter. For gauging parallel internal screw threads, different gauges are used.

Go gauge to check the tolerance on minor diameter and minimum effective diameter, whereas the NO GO gauge to check the tolerance and maximum effective diameter, these gauges are generally made up of special steel followed by hardening.