Step 1: What You'll Need
1/2-40 (NF) bottom tap and wrench
29/64" drill bit
13/32" drill bit
Half round file
Sand paper or cloth to finish/ polish (optional)
Rod (3/4" +) of whatever material you have and are comfortable machining.
For the material, I'm using aluminum. Delrin would certainly be easier, but I wanted something I could polish and make a little extra special.
You should probably check your dremel and make sure the threads are 1/2-40. Mine is threaded like that, but it's possible they've changed at some point.
Step 2: Start Cutting
The first few cuts are pretty basic.
First, face cut your material. Next, I cut the material down to.625" for the first 1/4", then cut an additional 1/2"(roughly) down to.750". The .625" is the same diameter as my flexi-shaft, and I figured the .750" would be a good size for the outer part of the cap.
Step 3: Shaping the Finger Side Contour
Step 4: Drill Main Through Hole
Step 5: Analyzing Flexi-shaft and Next Cuts
Next, cut the open end down to the right size.
After it's been cut, drill 29/64" for your tap. I drilled in .375" to give myself a little extra room for the threads that extend our from the shaft handle.
Step 6: Tap the Hole
I used a live center in the tail stock to hold everything centered, while I turned the tap with a crescent wrench (my small tap handle was too small, and my big one too big).
After you've tapped it, check the shaft handle and see if you need to counter bore the threads at all. I needed to a little, and bored out a 1/2" diameter .060" deep.
Step 7: Check to See If It Fits
Step 8: Shape the Tool End
Now rough the tool end of your piece to your desired shape, and follow with the file again.
Once you've completed this step, you're pretty much done unless you want to polish.
Step 9: Sand and Polish (optional)
I used 120 grit, then 320, then 400, then 600.
I followed this with polish and a soft cloth.
Because the tap presents a greater hazard while sanding and polishing, I covered the exposed parts with a few layers of painter's tape to keep it from suddenly grabbing the paper and cloth.