Pin Gauges & Plain Plug Gauges

What is a pin gauge and how are they used?

Pin gauges check holes or features are the correct diameter, in some cases up to 3 decimal places. It has a cylindrical body machined so a very specific diameter. Each pin gauge has a set length of 50mm. A distinction to make is that pin gauges should only be used to accurately measure diameter and not length.

A pin gauge can be used in isolation to gauge or inspect a hole diameter, or in tandem with a pin gauge handle to make a go/no-go gauge. In most situations, the actual diameter will be the smaller sized ‘go’ gauge and the ‘no-go’ gauge will be a size slightly larger than the ‘go’ gauge. Pin gauges are also available in sets for where various sized holes need to be checked.

What different types of pin gauge are available?

As standard, pin gauges are made from a hardened alloy steel (hardened to HRc62-65). These pin gauges can be made to any size with up to 3 decimal places of accuracy from as small as 0.2mm up to 30mm. Hardened steel pin gauges conform to a grade 1 standard, making them ideal for both workshop and inspection-grade applications.

Besides steel pin gauges, ceramic pin gauges are also available. Ceramic pin gauges have the advantage of being extremely wear resistant, corrosion resistant and have superior dimensional stability. ceramic pin gauges are also used where steel gauges cannot be used (such as in food produce, medical and aerospace industries) due to the conductivity of metals. However, ceramic pin gauges can only be made to 2 decimal places of accuracy. In most general applications, alloy steel pin gauges will suffice and the extra cost of ceramic pin gauges would be unnecessary.

Both steel and ceramic pin gauges can be supplied either individually or as sets with pre-determined sizes. Each set will contain a range of sizes and steps (could be either 0.1mm or 0.01mm steps depending on accuracy required). Pin gauge sets can be supplied in either 31, 41, 51 & 101 piece sets which will each cover a different diameter range. Standalone wooden boxes are also available should bespoke sized sets be required.

Furthermore, each pin gauge is supplied with a manufacturer’s inspection certificate which will detail the internal testing completed by the manufacturer. It will contain the actual measurements of that specific gauge and the tolerance with which it falls into. However, this is not equal to a UKAS standard of calibration, which will need to be completed separately. For more information on calibrating your pin gauge, please contact Cutwel today.

What is a plain plug gauge and how are they used?

Aesthetically, plain plug gauges look strikingly similar to thread plug gauges. However, plain plug gauges are designed for gauging the hole size of an unthreaded hole. A plain plug gauge would typically be used to check the fitment of a pin or dowel to a given tolerance. In most applications, a plain plug gauge would be used to verify the size of a hole (or minor diameter of a bore) before it is threaded. A thread plug gauge would then verify the thread size of the same hole.

Up to 50mm diameter, plain plug gauges are double ended, meaning one end is a ‘go’ gauge (the gauge that should fit inside a hole) and the other a ‘no-go’ gauge (the gauge that should not fit inside a hole). Above 50mm, the gauge will consist of two separate bodies; one body containing the ‘go’ gauge and the other the ‘no-go’ gauge. Both the ‘go’ and ‘no-go’ gauge will be made of a hardened steel substrate (HRc60-62) and will typically be to a H7 tolerance.

Custom gauges are available on request. This includes different tolerance classes for very specific or tight-fitting parts (e.g. H8, H9), as well as diameters to 3 decimal places of accuracy (e.g. 19.003mm) and different lengths.

Furthermore, each plain plug gauge is supplied with a manufacturer’s inspection certificate which will detail the internal testing completed by the manufacturer. It will contain the actual measurements of that specific gauge and the tolerance with which it falls into. However, this is not equal to a UKAS standard of calibration, which will need to be completed separately. For more information on calibrating your plain plug gauge, please contact Cutwel today.