[hikerbob (Bob)]

I've had my first go at cutting a worm based largely on idea's gather on this thread (and some previous research).

I used slice of 160mm round for the blank and the thread out of a car jack for the hob/worm.

I roughly machined a grove in the rim of the blank to try and increase the contact area. I ended up with 165 teeth (if my count was correct) and the mesh up seemed to go well. The cut's in the hob were done with a thin cutoff wheel in the angle grinder. I did not do any pre-indexing on the blank.

The support for the blank is part of an old Subaru gear box cut off and welded to another slice of the 160mm round. I've used holden trailer bearings because I had some and I figured that they are designed to cope well with a mix of thrust and side load. I machined the shaft for the support post out of an old trailer axle. I still need to set up a means to lock the shaft when I'm fitting a blank (and removing a worm gear).

I had not prepared the jack screw well enough. I should have machined a shoulder into it at the end held in the lathe chuck to stop it working it's way back into the chuck. I also should have used less side force, I broke the jack screw (thankfully at about the time I was getting ready to stop cutting). I was fortunate that the pieces included the section to be used as the worm. I'm not sure if this worm will go onto a mount but I'm planning to finish it for the learning exercise and if it works well enough I might use it.

I may have a go at cutting my own worm for a future worm gear but my screw cutting skills are not well developed yet.