Press Fit / Slip Fit Test Gage

A press fit between two objects prevents the two from separating without the need for adding E-clips or cotter pins or threaded nuts.. A slip fit allows a shaft to turn in a hole in the support structure without a need for adding a bearing.   

I was taught by my professor in school that the face offset for a press fit shaft in a hole was 0.2 mm and the face offset for a slip fit was 0.4 mm.  I found that these recommendations were somewhat generous and wanted to to find more precisely what the offset should be for each.

The plate mounts several shafts, each with a slightly different face offset from an 8 mm diameter.

I found that a slip fit required a face offset ofnegative 0.35 millimeters on the shaft and a pressfit required a face offset on the shaft of 0.15 mm. 

The gage includes an 8 mm inside diameter hole design on the flexible extension. This hole can be slipped over each of the shafts to determine which offset provides a press fit or slip fit.

The 8 mm hole measure actually 7.7 mm ID.

Note that a face offset of -0.15 mm provides a diameter change of -0.30 mm on a shaft or hole.