Extra Fine Threads or better.

[leeputman]

I am dealing with a frustrating project requiring super fine threads. OK, to be specific. I need to tap 1/4" plastic for a 22mm plug. The plug is supplied as is the tap M22 x 1.0mm. But the plugs fit too tight. I have been measuring and searching but no one sells this kind of stuff. I can find a tap once and awhile.

Instead of telling the whole story, I guess I am really looking for a machinist that really knows thread forms. No, not looking at some tables but really lives and eats thread forms.

Is there such a man? Or woman, wow, that would be my kind of woman.

thanks

PS the nature of the problem is that I am empowered to make my own plugs. But I would like to start with something. If I could buy all thread this fine or even machine bolts, the stupid plug is only 0.3" long. Then I could buy a tap to fit. I could then machine and fab. the plugs. I also need a supplier of items with this fine of thread. I am an instrument maker and my machinery is not up to the task.

[Geof]

I am dealing with a frustrating project requiring super fine threads. OK, to be specific. I need to tap 1/4" plastic for a 22mm plug. The plug is supplied as is the tap M22 x 1.0mm. But the plugs fit too tight....

I have no idea how likely it is you will find someone to make, or tell you how to make, an slightly oversize tap.

But here is an alternative: Cool every thing down, plastic and tap and tap it cold, below freezing, well below freezing if possible. The plastic will contract far more than the tap, of course, and also the plastic will be less flexible. A big problem tapping plastic is that it tends to flow around the cutting edge a bit so the threads do come out undersize. This will be reduced at a lower temperature.