The standardization of screw threads has been a historical endeavor involving several organizations. However, the ASME B1 Screw Thread Committee has emerged as the primary organization responsible for holding, updating, and curating these standards.

Gage accuracy depends on product info. Thread form plating changes pitch diameter. Compensate for buildup to make correct pre-plate allowances. 60° UN threads change pitch diameter by 4x plating thickness.

One of the more frequent questions we receive is: I am tapping a ¼-20 UNC 2B internal thread with an “H13” tap, what gage do I need to inspect the threaded holes in my parts after tapping?

Taper Pipe Threads are one of the more challenging threads to produce and measure. The ASME B1.20.1-2013 Pipe Threads, General Purpose (Inch) is the current standard that covers both the part thread specifications and the gages for NPT, NPSC, NPTR, NPSM and NPSL threads.

In my last column I listed some basic equipment requirements for the calibration of thread plug gages so I thought it would be helpful to give mating gages the same treatment. 

Screw thread inserts (STI) require the threaded hole to be inspected prior to inserting the threaded insert or coil. The dimensions and tolerances for the gages used to inspect these threads have been a bit confusing over the past 30 years. 

Thread classes for product threads, and by extension the gages used to inspect them, can become a bit of alphabet soup. Some find the requirements confusing.

Gage Assembly marks 65 years manufacturing special and standard thread gages with size capabilities run from 000-120 threads per inch to 15 ½ inch diameter and one thread per inch. 

Anyone in the fastener or screw machine business producing screw threads is familiar with ‘pitch’ micrometers. These relatively simple devices are often used to set up production equipment and monitor their output, but there are many misconceptions about them which can call their usefulness into question. 

The term “backlight” has two common meanings. One is a lighting product which is a planar uniform light source; the other is as a silhouetting lighting solution that may use that type of light source.