5/8 8tpi ACME tap possible loan?

Right bit of a long shot but if someone could help me out it would be much appreciated:

I would like to borrow a 5/8 8tpi ACME tap, I am loathed to purchase a new one as I have a feeling what I have in mind is not going to work!

I would like to use the tap as a crude gear cutting hob in order to free hob a bronze gear,

I did have it on my mind to actually make a hob and I did spend an hour in the shed realising that in order to make the hob I need to make so much other stuff that it was getting stupid! possibly all in vain if it doesn't work out! the tap will hopefully solve that problem in one foul swoop!

The aim is to create an 18tooth bronze gear that can run up and down a lathe lead screw in order to quickly traverse the carriage up and down the bed (exactly the same idea that myford used on the ml10 as a carriage traverse).

I would gladly cover postage costs if someone is able to help me out.

Many thanks and I look forward to your responses

William

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**

Will there be enough tooth engagement to keep the blank reliably synchronised with such a small gear..?

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

I found this by googling, it is slightly bigger diameter and I dont know if the helix angle runs on the correct direction.

**LINK**

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.

William,

A 1MOD 18T gear will probably do what you are looking for. 1.8" pitch is 1.011 module. The pressure angle will be incorrect unless you're lucky enout to find a 14.5PA 1 MOD gear but that should not matter overly much just for a handweel traversing gear.

Edited By Pete Rimmer on 07/08/2022 10:21:02

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