When using plug gauges for GO / NO-GO inspection, the GO member should fit into the work piece to indicate to the operator that the component meets the correct specifications. For this reason the GO gauge is usually selected close, but above the lower limit size of the component.
The NO-GO member should not fit into the work piece. If it does, this indicates to the operator that the component has been machined incorrectly and is out of specification. The NO-GO gauge is usually selected just under the high limit of the component, so as to stay within the part’s upper and lower tolerance.
Application Example: To check the center hole in the component for later mounting to center arbor for grinding.
Attribute to Check: Center hole bore diameter.
Center Hole Specification Limits: 0.235″ to 0.245″
The GO / NO-GO gauge is a quick, easy way to verify if this center hole is bigger than 0.235″ yet smaller than 0.245″.
In addition to the proper numeric size as illustrated above, the class of gauge also needs to be selected when ordering gauges. This selection process should be based on ANSI Standard B18.104.22.168-2001 (Plug Gage Tolerance Selection Guide) Our website offers a tolerance calculator to help with this selection of class such as ZZ, Z, X, XX. Gagemaker’s Tolerance Chart