Thread: Going in Circles

I'm making a Moxon style twin screw vise (the latest fashion it seems!) after a bit of research
I discovered that the best profile for wooden threads is a 90 degree form, so I made a tap.. 2" diameter 5 tpi 90 degree profile..




But what I really wanted was 3 tpi or thereabouts, but since I recut the nylon idler gear on the lathe last year after a crash, I couldn't get the change gears I wanted to work..
So time to make a new idler gear... This time it's 90t... the original was 80t before the crash.

I used some 6061 Aluminium, and since I had to make a center boss to support the bearing, why not use it to hold the work as well.
90t works well, since the gearing is 90:1 anyway.. one turn per tooth. The teeth are cut with a homemade fly cutter ground from a drill bit.





I wasn't careful enough with positioning the holes for the bearing block and cut through the sides when I counterbored for the 5mm cap screws.

The teeth were not too bad, but I had one fat tooth next to a skinny tooth and had to file the fat tooth a bit to get it running smoothly..
It's noiser than the nylon idler gear, but I guess that's expected. (I'm hoping it will get a bit quieter after it runs in for a bit)

Ok... finally I can do 3.4 tpi with the 47 tooth gear at the top and the 40 tooth gear at the bottom....

Now.... I can make a tap... then using the tap I can make a screw box, then with the tap and screw box I can make the wooden threads .....

Sometimes the only way forward is to go in circles for a bit..

Regards
Ray