You can make a very high quality stem simply using delrin tenons.Bear wrote:without the pimo tool, better to buy stems?
1. Create some hardwood jaws for your vice that simply have a V-shaped notch in each jaw. Use some grit-tape on the jaws to help them grab the piece of rod stock a bit better.
2. Clamp the piece of rod stock in the jaws, and lock everything in place--the table, the press head, the vise jaws, etc. Make sure your table is low enough that you can remove drill bits without having to lower or move the table. This is very important.
3. Use a 1"-1 1/4" endmill or forstner bit with the center point ground off to square the face of the stem. Remove just enough material to face the rod stock. Remove the endmill and insert a 1/16" drill bit (or smaller if you can put hands on it). Drill into the rod stock about 1". Do this in several passes or the expansion of the compressed dust will enlarge the hole and burn its interior.
4. Remove the rod stock and flip it around in the vise. Repeat the squaring process with the end mill. Using a 5/16" drill bit, bore a mortise hole into the rod stock approximately 5/16"-3/8" deep. Be certain to do this in one single pass and preferably at about 1000-1200 rpm's.
5. Take a 1/8" drill bit approximately 8" long. A standard length bit typically won't be long enough for some of the stems you'll want to make. Take this bit and, using a standard bench grinder, grind each flute to a taper so that the bit tapers almost to a point. This will alleviate there being a "shoulder" where the 1/8" bit meets the 1/18" hole.
6. Using masking tape, mark your drill bit approximately 3/4" shorter than the total length of the stem. Using multiple passes, and frequently clearing the bore hole, drill your 1/8" hole, making sure it goes deep enough to intersect your 1/16" hole.
7. Cut a piece of 5/16" delrin about 1 1/4" long. Drill a 5/32" hole through the piece of delrin. If you have no way of drilling other than using your drill press, you'll want to prepare the piece of delrin *before* drilling your rod stock. After drilling the hole in your delrin, you'll want to chuck it GENTLY in your drill press chuck, and spin it at about 1000 rpm's. Using a file, square the end of the delrin and then put a chamfer on the end roughly equivalent to the angle of your drill bit tip. This is roughly 15 degrees. Using about a 16 TPI (teeth per inch) metal blade for a jigsaw, sawzall, or even a hacksaw, cut three to four grooves in the delrin about 1/8" apart. Turn the delrin around in the drill press chuck, and repeat the squaring/chamfering process. DO NOT cut grooves in this end of the tenon. Once the tenon is squared, remove it and set it aside.
8. Taking the same 16 TPI saw blade (you may need to grind it to a narrower profile) scrape some grooves in the 5/16" mortise that you drilled in the rod stock. At this point, you're ready to join the tenon and the rod stock.
9. Mix some clear 5-minute fast drying epoxy, and apply a generous amount to the grooved section of the tenon. DO NOT apply the epoxy to the mortise of the rod stock. If you do, the tenon will simply act as a plunger, pushing epoxy all the way through the 1/8" draft hole toward the bit end of the stem. When you insert the tenon into the rod stock, it should actually require the force of a small hammer or mallet to seat the tenon all the way in the mortise. You should get squeeze out on the face of the stem at this point. DO NOT TOUCH IT OR TRY TO CLEAN IT OFF.
10. At this point you need to go back to the mixing palate you used for your epoxy and basically poke at it for the next several minutes until it reaches a certain curing point. Once it turns glossy and will no longer pull a thread when the mixing tool is pushed into it (a bamboo skewer works well if you don't want to make a permanent tool), you've reached the beginning of your "magic minute." During the magic minute, you can take your mixing tool and pull up the edge of your ring of epoxy "squeeze out." It will come up cleanly, and you can simply peel it off the face of the stem. If necessary, just use the bamboo skewer to scrape away any small slivers of epoxy that hang on at the joint of tenon and stem face. Some denatured alcohol on a shop towel will remove any residue left by the epoxy.
11. At this point, insert a 5/32" tapered drill bit into your drill press and drill the draft hole out stopping about 1 1/2"-2" from the bit end. At this point, you can remove your rod stock from the vise.
12. Now you must cut the inlet or slot in the bit end of the stem. Using a small 3/8" round saw blade for your Dremel tool, cut a shallow slot in the bit end of the stem with the 1/16" hole right in its lateral center. This can be done on a drill press using the Dremel blade if you don't have a Dremel tool.
13. Now chuck the 1/16" drill bit in your drill press or Dremel tool. If you have a Dremel with an extension arm and pen grip, chuck the pen grip in your vise, and chuck the 1/16" bit into the Dremel. NOTE: If you do have the extension, you'll also need the "quick change" chuck otherwise you won't be able to tighten the chuck enough to squeeze the 1/16" bit. If you're using your drill press, you will want to run it at its very highest speed. With the 1/16" bit in the chuck turn the machine on and drill back into the same 1/16" hole that is already in the bit end of the stem. Tilt the stem toward you so that the bit cuts laterally. Slowly pull the stem downward as you apply lateral pressure. Doo this several times until you reach the outer edge of your slit. Turn the stem around and repeat on the other side. At this point, you will have a thin smooth tapered slit that will allow you to file the bit to a very thin comfortable profile.
14. Now it's just time to clean up the inlet with needle files and sandpaper. For the remainder of the process, you're on your own. There are lots of ways to shape the stem, but ultimately you will end up using files and sandpaper to achieve the final profile.
Good luck!
Todd