Tapered Plug Gage

Plug gages have been used in industry for many generations to inspect circular components during and after production. Plug gages are used to compare hole dimensions or locations to specific tolerances. Go and no-go gages limit gages based on plus or minus tolerances from a specified dimension. Tapered Plug Gages use essentially the same process as regular plug gages except that regular plug gages are measuring a flat hole and tapered plug gages measured a tapered hole.

The tapered plug gage is often used for measuring high precision hole or slot dimensions. Tapered devices have a conical form. Plug gages with ball-shaped ends gage spherical cavities and tapered holes. Reversible gages allow both ends of the gage to be used for measurement. Some gages have plastic coated handles to absorb excess heat.

Application example:
Tapered bearings use the tapered plug gage to measure the cup component of the bearing assembly. Tapered ring gages are used to measure the cone component of the same bearing assembly.

Go / No-go:
“Go gage” dimensions are based on the minimum inside diameter (ID) of the component to be inspected. “No-go” gauge dimensions are based on the minimum outside diameter (OD) of the inspected part. Master rings (or ring masters) are used to calibrate and set up the tapered plug gage.

Tapered Plug Gage Types:
Pneumatic systems (or air gages) measure the change in pressure in air nozzles inside the tapered plugs.
Electronic gages use electronic probes to sense displacement of a stylus.
Mechanical gages compare physical movement of a gage spindle to determine part features and dimensions.

Specifying Tapered Plug Gages:
Attributes of the tapered plug gage that must be specified include the plug diameter, set range and set increments. Specify measurements in metric or imperial dimensions.

Tolerance by Class:
Class XX Gages = .001” – 0.08250” (tolerance no more than 0.00002”)
Class X Gages = .001” – 0.08250” (tolerance no more than 0.00004”)
Class Y Gages = .001” – 0.08250” (tolerance no more than 0.00007”)
Class Z Gages = .001” – 0.8250” (tolerance no more than 0.0001”)