A Set Fine Adjustment Screws of Bush and Screw

[october]

I am doubt about the fine thread (e.g M 6 x 0.25 pitch with 30 mm length) to match the bush (brass) and screw (stainless steel).

A set sample is given to do the prototype that no specification to guide. We do the reverse engineering to develop both bush and screw.

The problems as following:
- Bush is CNC turn with M6 x 0.25 pitch tapping and Screw is CNC turn with 0.25 pitch tool insert, I have no idea is it both method is correct? Any suggestion to improve?
- feeling loosing after matching both parts, tiny gap sense move up and down.
- feel stuck after lubrication apply and lubrication became dirty that screw thread in and out several times, seem like bush is wear off, tight a bit?
- Is it necessary to apply more lubrication to prevent loose sensing?
- Which method is best for inner diameter thread, tapping or inner thread insert?
- How to control both parts to fit together consistently?

I look forward the right method for suggestion improvement, even any suggestion how to inspect the fine thread bush and screw? Any resource support to do both fine pitch thread?

Hope I may get some info the standard specification (major dia., pitch dia. & minor dia.) of M6 x 0.25 pitch.

I look forward anyone to assist in this matter. Thanks.

Regards
October

[txcncman]

Machinery's Handbook for specifications is a good source.

Sounds like you are having problems with burrs on threads and they are being broken away when assembling the two parts together multiple times. For proper sizing, use GO and NOGO thread gages to check sizes after threads are well deburred/polished.

[fordav11]

the internal thread in the bush is set by the tap. it sounds like a custom thread (or possibly AF or BSF thread) so just cut the external thread to suit the tapped thread with a nice fit (i.e. not sloppy).
use a thread micrometer if you need more accuracy to measure the pitch diameter of the thread.