I don't have one of those forking banjos, either :
I was not sure how I was supposed to set these up, so I looked up the gearing for cutting an 18-pitch thread :
I needed a 32-tooth gear on the stud and a 72-tooth gear on the lead screw. I reversed the screw gear and bushing so it would line up with the large gear on the idler (the same one connecting to the stud gear). This turned it from a compound gearing to an idler gear.
Next, I chucked up a small chunk of cheap aluminum, because scoring from a tool cutter would show up easily, and it was soft enough I could rotate the chuck by hand. Then, I turned it a few times to get enough for a thread pitch gauge :
And measured it :
18 on the pitch! Success! Next, cut some actual threads. Again, I started with aluminum.
Next, I threw on my 25/64 bar I needed for a custom tap (yes, I had to learn all of this for a tap, which was for a stupid brass pen).
I removed it from the chuck and used a dremel to cut some relief in it (some of the reliefs I cut backwards, so beware if you make a tap), heated it up red-hot, and quenched it. I didn't care how hard it really was, because it had a single purpose - to cut some threads in a plastic insert to finish a brass pen :
For anyone who doesn't know about South Bend Juniors, that's how screw cutting is set up!
Next, I threw on my 25/64 bar I needed for a custom tap (yes, I had to learn all of this for a tap, which was for a stupid brass pen).
I removed it from the chuck and used a dremel to cut some relief in it (some of the reliefs I cut backwards, so beware if you make a tap), heated it up red-hot, and quenched it. I didn't care how hard it really was, because it had a single purpose - to cut some threads in a plastic insert to finish a brass pen :
For anyone who doesn't know about South Bend Juniors, that's how screw cutting is set up!
