Articles Tagged with ''thread inspection''

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.

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.

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. 

Screw threads are one of those important elements of mechanical design that are often taken for granted but find usage in critically important applications.

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.

Pick up any shaft or threaded fastener. How are you going to check it? An outside micrometer is most often the go-to tool for measuring diameters. A height gage or drop indicator could be used to check dimensions between part features, while an optical comparator is a good way to inspect thread forms or measure a groove width.

The basic concept of a thread plug is to provide a quick inspection for machinists and quality inspectors to verify that the threads are within the accepted tolerance so that it interacts with the mating part correctly. 

How do you measure an internal thread on a part? How do you decide what you need?