Original writeup from RobertSims at PBN
Level of Difficulty:
Medium (provided you don't loctite the wrong item
, everything can be reversed to stock, even after you are done)
-A clamping knob with female insert size 8-32
-Threaded rod size 8-32 (this is also called allthread). You should only need about 2 inches, but it's usually sold in 3 feet. Find a bunch of Mini friends and spread the wealth!
-Hacksaw with a metal cutting blade (You could use a Dremel with a cutting wheel, but it doesn't work as well - slow and easy wins the race)
-two wooden blocks
-(optional) tap and die set
1. Place the threaded rod in the vice between the wooden blocks. The blocks help prevent the threading from being damaged.
2. Using the hacksaw, cut the threaded rod down to approximately 1 1/4"
3. Disassemble your stock feedneck's screw, brass nut, and clamp.
4. Using the 1 1/4" long threaded rod you just cut, try to screw one end into the clamping knob, and screw the other into the stock brass nut that sits inside the clamp. If at any point it becomes hard to thread, use the tap and die set to correct the threading on the threaded rod.
5. Disassemble everything in step 4, then reassemble it on the feedneck. Test to see that the threaded rod is the correct size by testing the clamp's full range of motion and ensuring that the feedneck can be clamped down far enough. If needed, go back to step 1 to shorten the rod.
6. Disassemble everything again
7. Add A LITTLE red loctite to the hole in the clamping knob, or on the portion of the threaded rod that will screw into the clamping knob. Screw the clamping knob onto the threaded rod and let it dry overnight.
8. Assemble the new thumbscrew you have just made, the stock brass nut, and the clamp onto the feedneck.
-Your best friend is patience, a straight cut, and knowing that you can always make things shorter but not longer.
-With my personal project, my threaded rod extends just under 1" from the knob. You might decide longer or smaller is better
-On my first try, I decided that things would look better if I rounded the edges of the knob that would butt up against the feedneck so that the knob would have a better fit into the countersink of the feedneck. Unfortunately, with the knob I have, it just ended up looking bad because I wore the plastic down to the inner metal of the knob. Even if that had worked, getting back to a polished finish on the plastic is beyond my knowledge. Just leave the knob the way it looks, it's fine.