A brief procedure on the use of delrin tenons

[KurtHuhn]

First, decide on your tenon diameter. Most folks will use 5/16", but 3/8" and 1/4" are not uncommon.

Next, find a drill bit that's going to give you the right size hole for your delrin. As any machinist will tell you, 5/16" is not 5/16" from one drill bit or piece of stock to the next. In this case, you can count on the delrin being the same size, as these are manufactured to rather close tolerances. Like it or not, you're going to need to experiement on briar. other woods will not react the same as briar to drilling, and will not give you an accurate gauge of hole size. Scraps of briar are fine, as long as you can drill them using the same methods you intend to use when you make a pipe.

Have a selection of drill bits handy. Use bits from different manufacturers, as one manufacturer may have different tolerances than another. The design of the drill bits may also play a part in making a hole that's final size is different from other bits. Drill with these bits using the same methods of pipe manufacturing - the methods you use will be important in determining final hole size.

It's important to note that you MUST clear the wood chips frequently while drilling the mortis. If the wood chips build up, it will generate excess heat and pressure which will change the final hole size as those wood chips press against the sides of the mortis.

Once you have a drill bit that you know will provide a consistent hole size, you're ready to start using it. Be aware, that the bit that provides the right hole size for briar, may be to small for drilling a hole in vulcanite or acrylic. You'll need to be sure of your drill bits before you start.

My procedure is as follows:

Drill the briar:
- chuck the block in and line everything up along my construction lines for airway, mortis, and tobacco chamber. I drill the mortis/airway first.
- set the spindle speed for 500RPM or less.
- face the shank with a 1-1/4" precision Forstner bit. I take care not to use to heavy or aggressive a hand in this step. You want to avoid grain tearout.
- drill the mortis, about 3/4 of a turn of the tailstock at a time. This works out to about 1/12 or so of an inch for each advancement. After each advancement, I remove the bit completely from the hole, and clear all the dust and chips. The depth is roughly 1/2" inch when the mortis is completely drilled.
(at this point I continue on with the airway and tobacco chamber, that's not covered here)

Drill the stem:
- I chuck the rod stock and face with a 1-1/4" precision Forstner bit
- I drill the stock somewhat more aggressively than the briar. Vulcanite, Cumberland, and acrylic are more stable than briar under heat and pressure while drilling. Don't go too nuts here, because you can burn the mortis in the stem if you use too much pressure or speed.
- total hole depth in the stem material is about 1/4" to 1/2" depending on stem shape.
- I also use a bit that gives me a flat bottom in the stem mortis. This way the amount of epoxy in contact with the smoke is minimal, and the opportunity for a void at the end of the delrin is minimal.
- continue to drill the airway in the stem

Drill the airway in the delrin:
- Slice off a length of delrin approximately the length I need. I usually go about an 1/8" longer just to be sure I can bottom out the tenon in the mortis in the stummel.
- I set the spindle speed to about 1200 RPM to drill delrin. Delrin is extremely stable under heat and pressure, and is self-lubricating. This also mitigates any risk you might have of using too much forward pressure and setting the drill bit off-course.
- I do not face the delrin
- I use a short drill bit, or a jobber drill bit with most of it's length swallowed up in the chuck. This helps prevent the bit from wandering.
- after drilling, I use the tip of a skew chisel to cut 3 or 4 grooves in the delrin where it will be epoxied to the stem material. This is necessary, since delrin will not take adhesives very well.

Put the stem and delrin together:
- first, I take a triangle file and slightly deepen the grooves on at three points around the circumference. Do not depen the grooves all the way around. The goal is to get a slight triangle shape in the grooves so that the delrin will not rotate in the stem once the epoxy has cured. Just a couple swipes of the file in each groove at 120-degree intervals should be quite sufficient to hold it.
- mix up some epoxy (5-minute, 15-minute, 24-hour, whatever) with a toothpick
- use the toothpick to put a dollop of epoxy in the stem mortis
- spread epoxy all over the outside of the delrin. Be sure to get epoxy in the grooves and get all the big air bubbles out.
- insert the delrin tenon into the mortis. Epoxy will go everywhere, this is normal.
- at this point you can either wipe up the excess epoxy with a rag or paper towel, or you can wait a couple minutes and just peel it off when it becomes rubbery. Be sure to get it all, otherwise your stem won't fit right.
- after the epoxy has fully cured, you can remove the epoxy that got into the airway by carefully re-drilling the airway. I do this by hand, holding the stem and with a tapered drill bit turning on the lathe at 500RPM. BE CAREFUL!!
- now you can sand or file off whatever excess delrin there is so that you get a nice tight stem/shank meeting.

That's it in a nutshell. Sounds like a lot of work, but it goes rather quickly for me as I tend to batch most of that by doing 3-4 stems at a time. Way less time than trying to hand turn delrin on a wood lathe. I also prefer the buttery feel of delrin as a tenon over vulcanite - but that's primarily a personal preference.

[bvartist]

Thanks Kurt! I appreciate you taking the time to write out your procedure. Will be very helpful to those of us that are attempting to use delrin for the first time. I still think it will be a great time saver over turning tenons!

David

[alexanderfrese]

I often thought about putting together those sort of "interesting for everyone, but not so hot to discuss it all over again and again" themes to some stickies or in some subareas within the main themes. At some point it might be wise to distill some compendium od the forum's competences.

Kurt, go for pipepedia.com!

Just my thoughts…

[custom300]

Kurt,
Extremely helpful...Thanks a bunch.

[josh_ford]

Thank you so much Kurt, a whole lot easier than trying to tie together 20 different posts to figure it out!

[stevesriver]

Thank You, Thank You, Thank You.............

[LexKY_Pipe]

Thanks Kurt. Very helpful.

[JHowell]

Depending on the Forstner bit, I think it may be even more important to start the hole with a center drill. Some Forstners grab the block with the spurs and drag it around. Anyway, starting every hole with a good center drill is the most valuable tip I know.

JH

[custom300]

I purchased my first order of Delron last night http://www.onlinemetals.com. So, I'll let you know how it goes.

[KurtHuhn]

Depending on the Forstner bit, I think it may be even more important to start the hole with a center drill. Some Forstners grab the block with the spurs and drag it around. Anyway, starting every hole with a good center drill is the most valuable tip I know.

And that's very good advice. It prevents "bit flex" at initial bite, among other things.

The Forstner bits I use have a brad point, which makes it easy for them to stay centered, but useless where a small hole is desired in a perfectly flat face - like for facing the button end of rod stock.

[bvartist]

Just wanted to say thanks again to Kurt for writing out the procedure for using delrin tenons. Just completed my first stem using delrin. WHAT AN IMPROVEMENT. No cussing over my PIMO tenon tool and everything fit the first time!!!! And I absolutely love the feel of the fit of the tenon. Great stuff! I'll post a pic of the pipe when I get it shaped and sanded. But I'm a lot happier!

Thanks again Kurt, I really appreciate it.

David

[ArtGuy]

Depending on the Forstner bit, I think it may be even more important to start the hole with a center drill. Some Forstners grab the block with the spurs and drag it around. Anyway, starting every hole with a good center drill is the most valuable tip I know.

JH

By center drill are you meaning a hole started with a shorter drill bit to prevent the longer bit from wandering? Or is there a special bit called a center drill?

[munkey]

Special bits:

[Frank]

Also known as countersink pilot bits.

[bluesmk]

Kurt,
I agree, I prefer delrin's feel, but I also believe it's a value to the customer. What is probably the most performed pipe repair.....tenon splices!
Dan
Gabrieli Pipes

[giospro]

Thanks Kurt for the Info.
I just got my delrin a couple of days ago, so i'm going to try your method this week end.

Thanks

[MadTinker]

What kind of Epoxy is Used??

[KurtHuhn]

LocTite sells this stuff:
http://www.loctiteproducts.com/p/13/7/e ... Bonder.htm

It sets up in 7 minutes or so (longer for a full cure) and is designed for plastics. I stumbled on it by accident while looking for something else in the hardware store, and gave it a try. I won't use anything else now - it's damn near impossible to break the bond via mechanical means, and heating the stem hot enough to break the epoxy's bond would mean bad things overall for the pipe.

[GBMorris]

Please forgive me for reviving an old topic...

I am curious, why is delrin the preferred material for tenons?

Thanks,
Greg

[KurtHuhn]

Well, the preferred material is ebonite - as in an integral tenon made of the same material as the rest of your stem.

However, if you do not have the tooling to cut integral tenons, delrin is a great way to make professional looking tenons that fit every damn time without fuss.