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Hi Folks, I was wondering if I could please get some advice or comments on this stem. It's only my second try with acrylic. It has a delrin tenon.
Thank you in advance.

The internals need a bit of help. You have an hourglass inside the airway. This is common when you're getting started. Just take the slot tool and open it up a bit wider on the inside. I find a jigsaw blade (Needs to be ground down to fit) works great for that purpose. Acrylic tends to bend the slot tool a bit and makes it harder to get a good funnel deeper into the stem.

Then, to add comfort, flatten the sides of the stem so the stem is the same width from shank face to the button. Use a straight edge to see where the high spots are, then take them off with a pillar file or sandpaper fixed to a flat surface. While you're at it, take that same straight edge and make the top and bottom of the stem a straight line from the button to the shank face.

I can't quite tell whether those marks on the stem face are tooling/saw marks or whether that's a pattern in the acrylic. It looks like you could smooth that a bit better when you're inserting delrin. That will give you a bit better of a fit as well.

Thanks Jeremiah, I will work this lesson into the next stem project.

What are you cutting the stem face with?
One method is to use a forsner bit with a drill press, another is to use a lathe. The face should be finished before the Delrin is glued in.
Cylinders of wood or aluminum with pilots to fit the Delrin mortise and various grade discs of sandpaper glued to the face are helpful in smoothing both the shank face and the stem face in this case.
In addition to taking out the hour glass constriction, the internal slot need some TLC. Otto Frei has some nice needle files. The small round and small flat do a nice job with shaping and smoothing the inside of the slot.
In addition you can shape pieces of hacksaw blade to fit inside the slot and glue various grades sandpaper to smooth the slot internals. Round the straight edge of the piece of hack saw blade, fold the sand paper in a ‘U’ shape, glue it (I use CA glue), and you have 2 flat surfaces and a round edge for the corners of the slot. I use these wet.
DocAitch

Doc, I use my lathe to face the stem with an end mill and I also use my scraper. I always make sure the face is finished before I glue in the Delrin.
I have a few Kemper files I got from VFH that so far I have been using but as Jeremiah pointed out, I have found what he mentioned about the slot file and the acrylic to be true.
I am looking at the pillar files on the Otto Frei website. I'm lost as far as the numbers go and what they mean. Here is a screen cap pic of their pillar files.


Any suggestion as to size to buy?

I am referring to these needle files. They are tapered and will reach well into the funnel.
http://www.ottofrei.com/Glardon-Vallorb ... ustcol15=3
http://www.ottofrei.com/Glardon-Vallorb ... ustcol15=3
I recommend these in the 100-2 size - 100mm in length, number 2 cut. The higher the number, the finer the cut. The length is self explanatory, except to note that the thickness and width are proportionate to length.
Otto Frei also has wax saws which are slightly less aggressive than the funneling saw from VH, but which are longer. You can arrange your own handle to cut on the push or pull stroke.(I like the pull).
http://www.ottofrei.com/Mono-Tooth-Wax- ... de_size=20
I use the smallest -0.7mm diameter.
DocAitch

I guess the pattern on the stem face is the acrylic. If your lathe is a metal lathe, a facing cutter works well. If it is a wood turning lathe, I think there are folks on the forum who can tell you how to face the stem.
DocAitch

Thanks very much doc for the information. Now I have to try and absorb it all.

File length doesn't matter much. I use bastard files for roughing, then a scraper fashioned from a jigsaw blade. Then on to #2 and sometimes #4 pillar files on the stem. I use pippin and round files in #0 and #2 and a #2 round needle file on various other bits. A good file will last a very long time on wood and acrylic or ebonite. You can move to 320 grit from a good filing with a #2 file, and probably straight to 400 or 600 after the #4.

Thank you for the great help guys, I really appreciate it!

It's nice that this stem is translucent and I can see the slot and the funnel as it looks at the moment. I'm trying to work it down following the advice above. I took a picture and added some text to the pic. Was hoping y'all might be able to comment.
Thanks

I would aim to make the funnel as straight sided as possible, out to the end of the slot.
Yes, the constriction is the narrowest part, just below your arrow.
DocAitch

Gotchya man! Thanks Doc, I'm working on this still. Trying to at the very least make it clean up some.

The width of the slot should be determined by the funnel and vice versa. There's no point in having a slot if there's no funnel (sssh, don't tell Savinelli).