The Basics of Thread Ring Gauges

Many of us know what gauges are. But, for those who are new to this term, here is a brief idea to understand the concept of gauges. We use a lot of hardware to set up an instrument, don’t we? For example, we use nuts, bolts, screws, etc when we are making up a machine. These gauges are used to measure and help us identify the correct tools for our job. So, thread gauges are nothing but tools that enable us to measure the pitch of the screws and other threaded instruments.

Thread gauges are basically categorized into two groups. They are thread ring gauge and thread plug gauge. The ring gauges are used for measuring the pitch of the external threads. The plug gauges are used for measuring the pitch of the internal threads. The thread ring gauges are available in three styles. They are:

  • ACME
  • Straight Pipe and
  • Taper Pipe

ACME Thread Ring Gauges:

ACME Threads are used for translation motion in machine tools like lead screws where quick movement is required or in screw jacks, where the load to be shared is more. There exists a complete line of standard and special General Purpose ACME GO/NO GO thread ring gauges in compliance with ASME B1.5 - 1997. Acme thread gauges are used to gauge an externally threaded product. There are three classes of fit for ACME General Purpose thread gauges; 2G, 3G, and 4G.

Straight Pipe Thread Ring Gauges:

Straight pipe thread ring gauges are manufactured per ANSI/ASME B1.20.1. The threads are designed for free fitting mechanical joints. Straight pipe thread gauges include NPSM, NPSF, NPSC, NPSL, NPSI, NPSH, and NH sizes.

Taper Pipe Thread Ring Gauges:

Taper pipe Thread Ring Gauges are used in the application of pipe assembly, NPT L1 taper pipe ring gauges are used to check externally threaded parts. NPT L1 rings inspect the functional size or hand tight engagement of the pipe or male threads. NPTF L1 ring gauges are used to check externally threaded parts. NPTF L1 ring gauges inspect the functional size or hand tight engagement of the pipe, nipple or male threads.

Thread ring gauges are available as solid thread ring gauges. Solid rings are very dimensionally accurate as they measure the pitch diameter and minor diameter. They are designed generally in such a way that if they are dropped, they won’t need re-calibration assuming the threads have not been damaged. Since they are used to measure accurately, it must be used with excessive care and caution. A careless drop may affect the usage of the gauge negatively. Also, keep your ACME thread gauges clean and use a coat of an anti-rust solution. If it gets damaged, there will be no use for the instrument. Never force or gag it to anything. It can lose its integrity.