Hobbing your own Worm Wheel for Widefield tracker

[Jasp05]

Hi guys,

I've got an old EQ3 mount laying around that I was thinking of using for parts to make a small portable tracker from. Thinking similar design to a vixen polarie.

Due to sizing issues with my EQ3 worm gear and drive, it got me thinking about whether its worthwhile to hob my own worm wheel and drive.

Seen people do it online with just a thread tap on a lathe and have a disc cut to a predetermined radius to suit the number of teeth you want.

Would this be accurate enough for a widefield tracker?

[Stefan Buda]

Hi Aaron,
I have made a couple many years ago using spiral taps and pre-cut the teeth on a milling machine with dividing head. If you don't use a dividing head you may end up with the wrong number of teeth.

[Jasp05]

But as far as being accurate enough for the purpose below they should be fine?

I'm pretty sure it will take me a few go's to get it right. But honestly the number of teeth will not be that huge a deal as I can adjust the stepper to compensate. As long as its close t the desired number (150-200, haven't decided yet). I should be good.

[Stefan Buda]

Yes, the ones I made were accurate enough and even the periodic error was surprisingly small considering the pressure angle departure from the ideal (30 degrees instead of 20).
There is a rigid relationship between the PCD (Pitch Circular Diameter) and the number of teeth. If there is a departure from that, then there will be a hiccup somewhere along the circle where there is a pitch variation.

[bojan]

You can consider 3D printing (https://www.thingiverse.com/search?q=worm+wheel&dwh=135c4698d5ac4f4).. Should be OK for wide field AP and light loads, especially if finished with tool after printing.