Hi everybody,

Let me start by saying I am definately not an experienced machinist. I am a car mechanic by trade and sheet metalwork is my main interest. I am currently building a street rod from scratch to my own design. I have a Chester Crusader lathe and an XYZ Bridgeport clone mill. I mainly use the machines to make components for the car and tooling for my sheet metal machines.

I am currently designing a fixture/tool for my lathe to help me make some dies for my bead roller and section roll. Part of this tool will require a worm drive similar to that found in a rotary table. I have a small rotary table that I have dissassembled to work out the mechanics of the thing.

My question is this, the drum inside the table (worm wheel) has a pitch diameter of 90mm and 90 teeth, I assume this means it is module 1 ?

I need my drum / worm wheel to have a pitch diameter nearer to 60mm, should I use a module 1 cutter and cut 60 teeth or should I cut 90 teeth and if so what cutter should I use ?

Also if I reduce the diameter of the worm wheel by a third should I also reduce the dia of the worm by a third ?

Do I have to grind my own tool to cut the worm or can you buy tips to fit my tooling ( I have some tipped tooling for cutting 1.5mm threads ) ?

I do have the workshop practise series book 17 gears and gear cutting, but to be honest I find it a little gutty and find that every time I try to read it I sort of zone out and don't seem to absorb the information. LOL.

Any help would be appreciated regarding thread sizes and tooling / suppliers

Thanks very much

Neil