A Brief Introduction to Thread Gauges


When we think about durability, what comes to mind? Maybe Quality. Quality matters everywhere. Good quality ensures longer durability and less trouble. The function is measured with the help of a read gauge. A device that cross-checks the internal or external threaded portion or, in simpler terms, checks the thread. Tolerance, strength, durability, and reliability will decide the overall quality.

There are various thread gauges available. One of them is API 7-1, a widely accepted tool for measuring. Further, in this article, we will briefly understand the types available and how their usage differs from one another. So, without further delay, let’s begin the journey of knowledge and understanding. Here we go!

Understanding Thread Gauges Cutwel Ltd

Thread gage?

Before we delve into the types, let us have a bit more understanding of what exactly is a thread gage. These are used for measuring and inspecting the dimension of a specific pitch diameter or angle of an external or internal thread of an instrument. API 5B Thread Gauge is a specialized form of gauge used for inspecting the thread of an instrument inside out.

Each gauge type consists of two parts, one being a Go Gague, the other NO GO Gauge. For an external purpose, both types are needed. A GO gauge must screw into the internal thread for a restricted or internal inspection.

The types are…

  • Thread plug gauge

Master Metrology Thread Plug Gauge, M8x1.25-6H : Amazon.in: Industrial &  Scientific

This type of gauge is used to check the condition of the internally threaded part. The correctness of the pitch diameter is checked with the help of this gauge. The Go gage must pass through the but without any external force to be accepted.

  • Thread gage ring

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The gage ring consists of two thread rings, solid and adjustable. The tread depth and pitch diameter are corrected using this kind of gauge. A solid thread ring or screw is used to measure the externally threaded part. The Go gage must pass smoothly without any external force.

  • Thread caliper gauges

Matrix Adjustable Thread Caliper Gauge 5/16" BSF 18405 – The Vintage Tool  Shop, The Old Dairy, Carters Barn Farm, Piddlehinton, Dorchester DT2 7TH

This is used similarly for checking the externally threaded part, but to be honest, these are not much precise when it comes to measurement. A thread caliper is created with a familiar roller GO element which would help in sliding the element with the help of gravity. Plugs are required for the complete inspection of the size.

  • Thread pitch gauge

Screw Gauge Set SAE Whitworth 55 Degree & Metric 60 Degree Grip Whitworth  Screw Thread Pitch Gauge Measuring Gauging Tools|Gauges| - AliExpressTo begin with, this is not a typical acceptance gag. It does not decide the acceptance of the threaded part. Instead, a thread pitch gauge is used for visual inspection only. Usually available in a set of Slim plates with dedicated teeth specially created to given thread pitch. The teeth must match up closely with the part to be measured, with no gap; the pitch size becomes visible.


A good quality gauge will ensure that the acceptance of both internal and external threaded parts are done properly, and the quality is measured with utmost accuracy. There are various gauges available in the market, and one must choose according to the requirements.