How to make a hollow punch for making teflon washers

[OldMetallerParticipant @oldmetaller]

Gentlemen, I need to call upon your knowledge once more. A colleague is restoring a Class 50 diesel locomotive and he needs 180 teflon/ptfe/delrin or suchlike washers, 1mm thick by 34mm od and 18mm id. The ones he has priced are too expensive as he is on a budget, so I've said I'll make a punch for him to make his own washers from sheet material.

My question is, will mild steel suffice for this punch if he uses a soft cutting mat or something for the anvil, and is there anything I can do to the edges of the punch after I've turned it to shape to make it stay sharp for 180 punching operations?

Thank you,

John.

[OldMetallerParticipant @oldmetaller]

[David Clark 13Participant @davidclark13]

I would make a simple press tool. Two sheets of say 3mm steel with a 1mm + spacer. Bore the 18mm hole through both strips and make an 18mm diameter top hat punch from silver steel and harden it. Use a bench vice or similar to press the hole. Then put the embryo washers on an 18mm mandrel and turn the od.

[Clive HartlandParticipant @clivehartland94829]

I made a punch to make breathing holes in Bee Hive lids and turned a piece of EN8 and made 30 deg edge and then made a hollow rear set to match and threaded a hole through that and use a 10mm bolt to pull it through the 3mm ply. It cuts fine with no splintering at all. and it's been in use for about 10 years. I did not harden it.

For your needs I think you will need 2 punches, one for 18 mm and then a bigger punch with an 18 mandrel to guide the larger punch, again using the large vice as a pressing tool. A backing block to allow the 18 mandrel to go through as well. With 180 to make it's worthwhile making a decent punch tool.

Clive

[CirclipParticipant @circlip]

Think I'd be inclined to make a compound punch and die, OD and ID at one stroke. Punch – tube, 34 OD 18 bore, Die- 34OD plate with an 18dia centre slug mounted on a backing plate with pin ejectors.

If doing it the long way ie. separate P & D, punch the ID first.

Regards Ian

[OldMetallerParticipant @oldmetaller]

Thank you all for the ideas and suggestions. I'm going to attempt something to day, if it's not disastrous I'll post a picture!

Regards, John.

[Chris Evans 6Participant @chrisevans6]

Take a look at the Clark wad punch and copy the idea of a spring loaded centre. I am soon to make one for felt oil seals of similar dimensions.

[David Clark 13Participant @davidclark13]

You could possibly use a hole saw or two. Easy to cut the outside first then the bore and clean up on the lathe.

[KWILParticipant @kwil]

John,

You have a PM.

[Danny M2ZParticipant @dannym2z]

I recently made a punch using the info that I found here **LINK**.

Use the search function to find the article ' How To Make a Simple Gasket Punch ' , tick the box labelled 'Match all terms specified'

Another simple punch that I made a few years ago to cut discs worked much better by mounting it in a drill press and spinning it whilst gently pressing down (as opposed to just pressing it).

As for wear on the cutting edge, holding a sharpening stone against the side of the punch as it rotates works fine.

* Danny M *

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