Variable 3-disc indicating gages (circumferential backlash measuring instruments) VD measure the actual circumferential backlash in relation to the tolerance limit max. effective. For that reason circumferential backlash measuring instruments are fully toothed. The instrument is adjusted using a setting plug.
There is no standard method of inspecting the circumferential backlash – it is specified in the standards ANSI B92.1 and ISO 4156 as a special inspection method.

Fully toothed no-go gauges are the basis for circumferential backlash. They are listed in these two standards as special inspection methods „Alternate A“ and „Alternate B“. Circumferential backlash measuring instruments can be used instead of fully toothed no-go gauges.