Thread gauges and metric thread gauges

If you are new to screws and gauges, you need to know everything about them before you start on your project. Screw and nut inspections use a wide variety of gauge types, which can be confusing to someone who is unfamiliar with threaded part inspection and metrology. Language and significance can be difficult to grasp. Here, we'll go over this in a clear and concise manner.

No-go and go-no-go snap gauges are used to quickly inspect cylindrical parts in a production shop, such as shafts or holes, for passing inspection (for checking holes). They are simple and straightforward in their application.

Thread gauges are used in production shops to quickly check "screws" (externally threaded parts) or "nuts" (internally threaded parts) for inspection and approval. Thread gauge terminology and application can be confusing to a novice metrologist when looking at the metrology of the threaded parts as a whole. There are several different thread gauge types.

This includes the major and minor diameters of the thread as well as the pitch, pitch diameter, pitch (in metric terms) or threads per inch (in SAE terms), the flank angle, and more. In most cases, a GO/NO-GO type of threaded gauge will examine a threaded part primarily based on the pitch diameter. Until a GO gauge is answered and a NO-GO gauge is not answered, the threaded part is deemed acceptable and will pass the inspection. GO/NOGO gauges (like those used for measuring cylindrical parts) may also be used in some cases where the thread's major diameter (for screws) or minor diameter (for nuts) is critical to the acceptance of a threaded part.

The acceptance of a "nut" is checked using metric thread gauges (an internally threaded part). When working with small threaded parts, the gauge will be double-ended, with the GO gauge on one end and the NOGO gauge on the other end. It's possible to have separate pieces for larger parts. Using a thread plug gauge, you are able to measure the diameter of a thread's pitch. An inspection and acceptance of the part require that the GO gauge passes through all of the nut's length without the use of excessive rotational force. Using the NOGO gauge, the nut can only be entered over a maximum of two turns.

Understanding the factors that influence the use and actions of different gauges will help you get the right things for your project.