Cylindrical plug gages, sometimes referred to as pin gages or plain
plug gages, are used to check a drilled hole or the minor diameter
of a threaded hole. There are three (3) basic styles of cylindrical
Reversible Pin size range: 0.015" to 1.010"
Taperlock Plug size range 0.240" to 1.510"
Trilock Plug size range 0.760" to 4.510"
The attraction of the reversible is that it affords the end user
the opportunity to double the wear-life of the gage by simply turning
the gage around and using the other end, resulting in lower gage
cost. The reversible cylindrical pin gage is designed for size ranges
of 0.015" to 1.010".
The taperlock design is held in the handle by means of a tapered
shank which provides added holding strength necessary for intermediate
size ranges of 0.240" to 1.510".
The trilock design may be used like a reversible by simply turning
the members around. A bolt fastening system is used because of size
and weight. The trilock is designed for size ranges 0.760" to
Double end pin and plug gages are supplied with ( + ) plus tolerance
on the GO member and ( - ) minus tolerance on the NOGO member. Cylindrical
plug gages may be furnished in four (4) tolerance classes, as follows:
Class XX - Very close tolerance and typically used for master gages.
Class X - Close tolerance for products requiring the highest grade
of precision (most commonly used).
Class Y - Larger tolerance than class X and used as working gages.
Class Z - Used as working gages for more liberal product tolerances.
When selecting gage tolerance it is a good practice to not exceed
10% of the product tolerance, half for the GO and half for the NOGO.
Following are examples of tolerance comparisons for cylindrical
This page is a modified page extracted from Dynamics of Gaging published by Regal-Beloit Corporation.The data is provided for general information only. The intention is to provide accurate information; regardless; errors may exist in the supplied information. If accuracy is critical, base your final decisions on the data provided in the root documents: ANSI/ASME B1.20.1; ANSI B1.20.5;and ANSI SAE AS71051 which are copyrighted documents. To purchase copies visit an Authorized Reseller.
Original Posting: 5/4/2005
Last Revision: 5/5/2016
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