We make electrical connectors for aerospace customers. These connectors often use screw machine contacts. In other words, the contacts are made using CNC lathes.

My question is: What is the best way to dimension the contact to control its form, fit, and function?

I have seen TOP, Runout, Concentricity, as well as no GD&T specified on drawings in the past.

During manufacture, they obviously rotate on the lathe collet but in final application/function they are stationary inside connector insert blocks. Any comments or advice is appreaciated.

Position can be applied with material modifiers which allow a bonus tolerance and possibly a datum shift to come into play (extra tolerances).

Concentricity can NOT use a material modifier (less tolerance = more expensive parts) and is generally reserved for cases where part balance in essential.

Runnout also can NOT use a material modifier. Runout is ONLY used to control surfaces constructed around or perpendicular to datum axis.

Finally no GD&T is always the wrong answer. GD&T was created for the modern Engineering / manufacturing world, and allows larger tolerances as well as a clear interpritation of the design intent. Omiting the GD&T is like throwing money out the window.

That with a clear understanding of Rule Number 1, perfect form at MMC, along with how to refine the tolerance normally with regard to form or orientation and you can clearly define your need.

The many other tolerance callouts are still useful, but typically more expensive and often not really understood. So I suggest simplifying with the callouts above and limit any confusion in interpretation.

Using no GD&T? Then why use anything at all? You might as well just tell a supplier/manufacturer to do the best ya can.