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Haven't tried this yet but how does delrin react to heating and expanding with a Pimo tenon expander or the old heat and push against the wall technique? Anyone tried it?

It has a strong memory and tends to return to it's original shape/diameter with very little heat. It does the same when heated and bent.

Thanks for that. Appreciate it. Has anyone ever been able to expand a delrin tenon and get it to work?

I have. I do delrin tenons of 3/8 and turn them down to 1/4 for most of my pipes. I do this because I like the extra surface area that 3/8 gives for gluing. On a few occasions I have taken the extra pass on the tenon when reducing the size and in so doing made the tenon a tad loose in the mortice. When this happens I insert a plug gage one size larger than needed, which expands the tenon just a bit, heat the delrin with gun, cool in water, insert the next larger size plug gauge, heat and cool. After each size I try the fit. Usually after a couple of over sized plugs it will fit nice and tight. Don't think I have sold one of these yet but all my completed pipes have spent the summer in the trunk of a black car in Texas heat of over 100 degrees for the past two months. They are all still nice and snug. I can't imagine the heat from smoking at the mortice/tenon connection to be more than the heat generated in the car trunk in Texas this time of year. bob gilbert

Bob,

That's a great tip! Thanks for posting it!

Todd

I think the Texas car trunk heat is a pretty good test....

The delrin/acetal should not be trying to distort until you hit near 340F.

If you have any memory issues (not you, the delrin), it is probably because it did get hot enough when you expanded it. This MSDS sheet has a bunch of info (including the melting temp) on it if you are curious http://www.sdplastics.com/delrin/delrin%5B1%5D.pdf.

Keep in mind, I've never expanded a delrin tenon, but I've had a fair amount of experience with plastics, so that should be worth something.

If you are wanting to know more about Delrin it is actually made by DuPont. The more general name is acetal.

Let us know how it goes!

I've only tried to expand a delrin tenon once.... to no avail.

Thanks for the discussion and tips. I will give it a try and let you know how it goes for me.

I did expand a delrin tenon which I had turned just a hair too small. I used a scratch awl found at Ace Hardware. I warmed the tenon with an alcohol lamp then inserted the awl. Just kind of eyeballed it. Let it cool off. I think the tenon then contracted slightly. Had to do it one more time and let it cool again. Fortunately it worked. Granted, it does not respond like rubber but it can be done. Thanks again all.

Fantastic!