Using Delrin Tenons: Difference between revisions

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.

- 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

- 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.

- 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.

The diameter of the Delrin used for the tenon will largely depend on the pipe's final stem and shank diameter. It is critical that your drills match the Delrin you're using, especially with regard to the fit of the tenon in the stummel mortise. Both drills and Delrin very slightly, so some experimentation with speed, feed rate, and different drills, even of the same marked size will result it the best fit. Once you find a good drill, make sure you keep track of it. It may be advantageous to  use a different drill for the stummel than the one used for the stem material.

===Preping the Delrin===

Now that our epoxy is fully curred we can fit the Delrin tenon to the mortise. First bevel the tenon so it will not damage the mortise in the stummel, then check the stummel and measure how much to trim off the tenon:

The draft hole can be sanded up though most of it's length by wrapping sandpaper around the 1/16" drill bit. The final 3/4" or so cannot be reached, but it will be carefully opened, filed, sanded, and buffed later. Steel wool does a nice job cleaning up the tenon end after the sanding.