I have challenged myself to make a worm gear from scratch.
To buy a decent worm gear set could set you back a few hundred dollars and for that amount of money you can almost buy a second hand telescope mount to do the job of tracking a camera for wide field long exposure astrophotography. My previous camera tracker used a stepper motor with a small worm and belt gearbox but it was not accurate enough and was causing up to 25 arc-seconds errors in tracking accuracy in RA (right ascention). Look at two of my previous posts to see what I have done before:
So, the challenge is to take a small slice of stock bar aluminium and machine a worm gear set that can be used directly with a stepper motor to drive the tracker. I aim to reduce the number of moving parts and to make the gearbox as solid as possible to prevent tracking errors. My aim is to get a tracking accuracy of plus/minus 5 arc-seconds.
I tried making a worm gear with a 65mm diameter aluminium disk to see if I will be able to do it. This was the result:
Raw aluminium disk (65mm diameter, 15mm thick)
I then milled the flat surfaces smooth and drilled a centre hole (10mm). As the centre hole will never be exactly in the centre of the disk I had to turn the disk on a lathe. This was a bit of a problem because I don’t have a lathe, I only have a small mill. Well, I made a plan and used the mill as a lathe. It worked fine.
I then used a M10 tap to cut the worm gear, this was quite exciting and took about an hour and a half.
The end result was not bad at all. There are 132 teeth with a 1.5mm pitch. I am quite happy that this worm will work reasonably well. I just have to scale the process up to a larger aluminium disk.
I have now obtained aluminium disks, 130mm diameter and 14mm thick and will try and repeat the process to get 270 teeth. Using this gear with a stepper motor running 1/16 steps should work out well. Watch this space for progress …..