Tapping help needed!

[Tangoman]

Folks,

I have been trying to make a custom pen and have hit a few snags and need to pick your collective brains !

I have been making a section to suit a rollerball, I cut a tenon at 10.2 m&m for a 10 m&m thread, when I have finished it it measures out at 9.6 mm across the threads - is this normal or is my die too tight ? When I screw it onto a piece in the chuck to hold it which has a thread cut with the corresponding 10 mm tap it basically wobbles until it butts up against the holding piece. What's going wrong ?

The taps and dies are from a set bought from trade tools and have had no use other than this.

Also, is a ten mm thread too narrow to use to join a section to the body, should I be using 12 mm?

All help appreciated !

Cam

[Big Shed]

First off, 10mm is about right for a section to body thread, but it would depend on what cap to barrel thread size you are using. Remember that all these thread sizes are inter-related as you need to have enough wall thickness left. If you started with a 12mm section to barrel thread, you would finish up with quite a fat cap.

Not quite sure why you using an OD of 10.2mm to cut a male 10mm thread? If you start with 10.2mm you are forcing the die to cut the OD as well and it is probably cutting more than you need. If you are doing this in resin than especially so.

You should be using 10mm for a 10mm die.

It is quite normal for the male threads to measure smaller than the nominal size, just go and measure a few bolts you buy from the hardware store and you will see what I mean.

If when using the 10mm starting point your resulting male thread is still too "sloppy" then by all means open up your die a bit.

[Tangoman]

Big Shed,

Many thanks for that info ! I will keep working on this and see what happens.

Regards,
Cam