I'm trying to figure out which involute gear pitch works with 8 and 10 TPI ACME thread? By "work" I mean for low pressure application similar to a lathe thread dial or other low torque application.
Some one on forum posted using a tap as the work and cut a worm gear. Then turned the worm to match the tap. As PMartin noted, the worm gear would ideally have a radius matched to the worm for more tooth contact.Your gear will need to be quite narrow to even work at all. Worm wheels (your gear) have teeth that have an angle that matches the angle of the thread helix. You won't have that with a regular spur gear.
You are right ... and I need to do it right. I have a PM935 mill and Z axis lock is crap. There are two lock screws/handles located on the left ways. Locking them is getting tedious. My initial thought was to replace the handles with small gears that interface with a vertical Acme threaded rod with a handle at the top. One light twist of the rod to rotate each way lock screw (timed of course). Time is money and messing around under the table to tighten lock screws is a poorly conceived shortcut on an otherwise perfectly mediocre machine.Your gear will need to be quite narrow to even work at all. Worm wheels (your gear) have teeth that have an angle that matches the angle of the thread helix. You won't have that with a regular spur gear.
Can only guess how the 2 gib screws are situated on your machine as I'm not familiar with the PM935 mill.
The Bridgeport uses a single lock which has a taper that bears against the knee gib when the front handle is rotated up.
"Tming" 2 screws to advance evenly is not going to be easy. Using indexable (or adjustable) handles with external threads to match what's on your mill might get the job done if they are linked in such a way so that they tighten up evenly. The linkage(s) would have to have an "evener" (think of a single horse evener , but in reverse) to allow some leeway between the handle positions. A lever with an eccentric or screw/nut assembly could then be attached to pull the center of the evener to employ the locks.
Check out some indexable/adjustable handles on McMaster-Carr or on Amazon, to name a few sources.