I see that the Tracey Tools one is £35, I have a 3/4 x 5 RH and need the left hand version. I would not like to try a 5/8 x 8 into bronze, the tap could easily break with the extreme torque needed. You might try Kingston engineering, they do nuts in several styles.

**LINK**

If you have a lathe which can singlepoint 8 per inch, why not cut an ACME thread and slot it axially to make a cutter for bronze. I could lend you a 16mm tool with an 8 ACME insert in it. Your 18 tooth gear would be just under 3/4" diameter, so Diogenese is right to be concerned about such a relatively coarse thread being able to cut sucessfully.

There is already a thread on a similar subject, "square thread" running at the moment.

Edited By old mart on 17/07/2022 20:02:10

Edited By old mart on 17/07/2022 20:06:06

The last reply was about three weeks ago so you may have it all sorted now, but I am not certain free-hobbing would be an easy or reliable way to make a small-diameter, large-pitch worm-wheel. At least not without gashing the bulk of the metal out first.

(A gear-hobbing machine rotates the blank against the revolving cutter, in a positive, controlled manner.)

I've not tried actually cutting metal, but looking into it as a option for one of my projects, it seems very difficult to maintain accurate pitch that way. Especially for use as a traverse gear where you want it to be mesh smoothly at any point in its rotation.

I agree with Pete, it may well be possible to get away with a narrow spur hear of appropriate size. I also agree with Nigel; if an accurate worm wheel in terms of diameter and tooth count is needed then gashing is essential before finishing by free hobbing. For example, worms and worm wheels (worm wheel is approximately 4" diameter):

Home made hob:

Gashing the blank (note that gashing removes most of the material, allowing the hob to go directly to almost full depth):

Free hobbing to generate the final tooth form:

Andrew