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Tenon stuck in stem

Posted: Sat Apr 09, 2016 4:37 pm
by Ratimus
Hey, so I've got this delrin tenon. I cut a series of deep grooves in it around the circumference so it wouldn't come out of the stem once it was glued in. I glued it in. Stem is almost finished; during bending it got hot enough to break the bond with the epoxy. Now it rotates but is still mechanically held in place.

Hey, spinner stems for gangster pipes! Sure to be the next big thing. Next time I'll make sure and cut my grooves perpendicular to the ones I've already done. Lesson learned. Anyway if someone liked this stem but didn't particularly care for the new feature, how might one attempt to remove the tenon so he could glue in a new one (one with ridges cut both directions)?

Re: Tenon stuck in stem

Posted: Sat Apr 09, 2016 5:22 pm
by Ratimus
Okay, I solved this one by manually drilling out the tenon. I started with bit 1/64" larger than the airway and ended 1/64" smaller than the mortise, then I used a dental pick to peel away the ultra thin layer of delrin that was left and finally rammed out the leftover epoxy. I stuck a pipe cleaner into the stem from the button side to keep epoxy out of the airway, then glued the new, pre-drilled tenon in place, pulling the pipe cleaner through from the tenon side. I pulled another pipe cleaner through and it came out clean. In all, a much easier fix than I expected. Glad I didn't have top start over on that stem!

Re: Tenon stuck in stem

Posted: Sun Apr 10, 2016 5:56 am
by wdteipen
A good example of why you have to cut grooves both directions. FWIW, I've gone back to integral tenons.

Re: Tenon stuck in stem

Posted: Sun Apr 10, 2016 6:03 am
by caskwith
Threaded tenons FTW.

Re: Tenon stuck in stem

Posted: Sun Apr 10, 2016 6:43 am
by LatakiaLover
I've said this here many times: I get sent quite a few pipes with pulled-out Delrin tenons.

It is trickier---more demanding of proper technique & materials---to glue Delrin tenons in a bullet-proof way than many people think.

I recommend either doing what Wayne decided or put in the work to do Delrin right. Heavy, multidirectional scoring (or cross-hatched threads) on all surfaces that come in contact, completely filling the scoring with adhesive, and use a good brand of slow(er) curing epoxy, not the 1 or 5 minute quick set stuff.

Re: Tenon stuck in stem

Posted: Sun Apr 10, 2016 5:05 pm
by Ratimus
I use 30 minute epoxy. I usually score the delrin in multiple directions but I thought if I cut deep, angled grooves I might not need to do the every direction thing. Wrong. I'm just super glad it failed early and didn't leave the shop to become a blight on the world and my (nonexistent) reputation. :oops:

Re: Tenon stuck in stem

Posted: Sun Apr 10, 2016 5:55 pm
by Sasquatch
Nope you really need to waffle the tenon and try to score the mortise wall bad as well.

I use dental picks for the mortise, and little scrapey files, you could use a tiny dremel bit too... outside the tenon I manually cut grooves with a carving gouge, and sand the outside of the thing (on the gluey end only of course) with 100 grit just to sort of fuzz it up. If you have ever tiled on Schluter's "Ditra" cloth, that little fuzzy texture is enough to hold tiles, it's helpful to hold the tenon too!

But really you need a 100% multi-directional mechanically fixed bonding surface in there, and there's only one way to find out if what you have is working! :lol:

Re: Tenon stuck in stem

Posted: Sun Apr 10, 2016 6:18 pm
by LatakiaLover
Sasquatch wrote:Nope you really need to waffle the tenon and try to score the mortise wall bad as well.
This. ^^^^

Get after the walls of the "socket" the Delin tenon will be glued into AND the entire length of rod that will '"disappear" into the socket with one of these:

http://www.ottofrei.com/Store/High-Spee ... -10mm.html

or these:

http://www.ottofrei.com/Store/High-Spee ... -00mm.html

No need to be artistic, just make divots with it. Deep ones. Everywhere. Both pieces.

Then, when applying glue, be sure the divots are filled. Press in, scrape off. Think asphalt in potholes. Only then cover both components with a thin, overall coat and push them together.

Remove excess with whatever improvised tool you like, and then go after everywhere there was excess with a rag/paper towel/etc. that has been BARELY dampened with white distilled vinegar. (NOT wet with it---that will make the seam cloudy when the epoxy cures). Repeat with a pipe cleaner to clear the airway of excess.

Re: Tenon stuck in stem

Posted: Sun Apr 10, 2016 8:19 pm
by Sasquatch
I just re-drill the airway. Which is to say, I prepare a tenon, drill it out etc, and glue it into the rod with the rod chucked. Then after I can cut the tenon to lenght, chamfer it etc. Then I just re-drill the epoxy out and drill the airway into the stem. But this is a "set this up overnight so you can do it in the morning" method, not appropriate for every application.

Re: Tenon stuck in stem

Posted: Sun Apr 10, 2016 9:50 pm
by LatakiaLover
Sasquatch wrote:I just re-drill the airway. Which is to say, I prepare a tenon, drill it out etc, and glue it into the rod with the rod chucked. Then after I can cut the tenon to lenght, chamfer it etc. Then I just re-drill the epoxy out and drill the airway into the stem. But this is a "set this up overnight so you can do it in the morning" method, not appropriate for every application.
I used to do it that way until getting burned. A plug of epoxy broke free and stayed in front of the drill. Little bastard spun and slid but would not come out without triggering a half-hour's more work.

Now I use a cleaner as a prelim to guard against a sliding plug, then use a drill bit to clean up the airway walls after everything has cured.

Re: Tenon stuck in stem

Posted: Sun Apr 10, 2016 10:12 pm
by Sasquatch
LOL yeah that would suck.

All in all, I find Delrin so easy and "pretty" and the fit so nice that I've started using it a LOT more recently. One of the convincing features for me is the fail-point - okay, so the thing falls out. Well, no biggy, glue it back in. It makes repair a snap, but honestly I think the chance of a delrin tenon breaking is tiny. I use them particularly on tiny pipes, getting that ultra-smooth mortise fit so you don't feel like you are going to snap something.

Re: Tenon stuck in stem

Posted: Sun Apr 10, 2016 10:47 pm
by wdteipen
I actually had a customer return a pipe for repair with a broken Delrin tenon. It was the weirdest thing. It broke like acrylic. I have no idea how that is possible unless there was a hidden defect in the Delrin. Very strange.

Re: Tenon stuck in stem

Posted: Sun Apr 10, 2016 11:03 pm
by LatakiaLover
wdteipen wrote:I actually had a customer return a pipe for repair with a broken Delrin tenon. It was the weirdest thing. It broke like acrylic. I have no idea how that is possible unless there was a hidden defect in the Delrin. Very strange.
I'm going to speculate that one of the texturing scratches/cuts happened to exactly align with the face of the stem. Delrin will indeed break cleanly like glass when glass cutting techniques are used, just not reliably.

Re: Tenon stuck in stem

Posted: Mon Apr 11, 2016 9:08 am
by pipedreamer
I use a dremmel with carbide bits and J.B. Weld and mount on the lathe for a little pressure!!! Works for me,,,

Re: Tenon stuck in stem

Posted: Wed Apr 13, 2016 2:43 pm
by mightysmurf8201
I once had a mishap while drilling a stem that had the delrin already epoxied into it(pretty much same procedure as Todd's). I won't get into the particulars, suffice it to say that I didn't secure things as well as I should have on the lathe, and I ended up snapping the drill bit and shattering the tenon. There was also an airborne Jacob's chuck. The big take away, aside from ensuring your tools are properly set up, is that the part of the delrin that was epoxied into the stem, was still securely in place. This experience solidified my belief that when properly done with a mechanical bond, delrin is an awesome material that will hold up under normal use, and sometimes not so normal use.