Have a look on HPC gears website, they may have a standard or be able to make you one. They are based in Chesterfield UK.

I see that GHT's dividing tools will do 93 divisions.

Hi Vic

I had a couple of gears cut for 'my' Fortis a few years ago by Glasgow engineers, straight forward and painless. I cannot remember the DP and so on I worked out but will see what I have left after my recent tidy up. Let me know if Glasgow is suitable or within posting range.

M

Are you sure it's 93. – count again. Introducing a prime of 31 into a gear chain makes no sense at all. If the number 93 is cast onto the gear it might just be the part No, I have some gears like that just to confuse.

I assume it is the same as the pictures on Lathes.co.uk so this gear meshes with a smaller one on the gearbox input and they would be best as a 4:1 ratio. 96 or 92 are much better options. If 92 then the other two gears can be a 2:1 ratio for which 38:76 fits nicely.

Howard,

These lathes were produced in the 1940s and 50s so I would imagine them to be 14.5 degree pressure angle. Furthermore, they were I believe based on the US Clausing of the 1940s which would almost certainly have been made to that PA.

I think it a fair bet that the 'clone' would be as little changed from original as possible.

I hope that helps

Regards Brian

If you don't make your own you can get a suitable 2nd hand gear, chain drill a ring about 1/2" inside the teeth then chuck and bore the drilling holes away leaving you with a ring gear.

Chuck you busted gear and turn the teeth off to close ish fit to whatever you bored the ring to. You need room in the joint for Loctite so not too tight a fit. Once set drill and tap two M6 holes on the joint line for bolts if belt and braces appeals.

This keeps all the existing gear center keyways, bore size etc etc

I've done this on a back gear it's not that hard.

The use of holesaws was discussed in a thread here some time ago when the interesting point was made by someone that (with the right setup) no pilot drill is necessary. I favour rotabroaches for this kind of job but they are much more expensive, particularly in the larger sizes.

I needed to remove the centre from a 4" diameter by 1" thick cast iron blank the other day and successfully achieved this with a 64mm holesaw ending up with a useful piece left over. The operation was done in the lathe, reversing the work at the halfway point to avoid hitting the chuck jaws although it looked to be possible to get through at one setting. A lot of torque is needed for this and I had to use a strap clamp to release the keyless chuck.

My impression is that this method is less successful with steel where the chip is less easily cleared from the cut.