Availability of a T33 & T34 Myford Change Gears?

Great information there gentlemen.Thank you.

Yes it is indeed the later model I have.

All indicators for such are present.

Brian - good afternoon to you. I was hoping you'd be able to chip in with a more coherent explanation of this than I managed, thank you.

I feel I ought not to let the concept of a 33.5 T gear pass into Myford myth. I hate to spoil a good story, but it was a 16.5T gear (or the functional equivalent thereof) John and I devised.

In fairness to everyone who has contributed this is a red herring, as we've established that the gearbox is the later type and thus the 33 and 34 T gears will offer the neat and workable solution for cutting the common metric pitches for which they are rightly popular. I was concerned not to assume that Frank's lathe and gearbox combination were contemporaries, as there would be a whole world of confusion awaiting if someone had fitted an old gearbox to a late date lathe.

As to sourcing the 33 and 34T gears, hopefully the forum can provide. Unfortunately I can't help at the moment, or at least not until after Christmas as I'm part way through a project for my nephew for his Christmas present, and I beginning to wonder if I've bitten off more than I can chew!

Best regards, stay healthy!

Simon

Hello Simon,

Nice to hear from you again, this seems to be the only topic we occasionally meet over

Thank you for your correction on gear tooth count, please put my mistake down to a "Senior Moment" that the late Terry Wogan so neatly devised to cover such situations. It is as well not to let a new Myford myth develop, it seems to take so little for it to happen!

In this case the situation doesn't arise, the thought of an old gearbox being fitted to a newer model lathe would introduce a whole new level of confusion. I recall a posting several years ago now where calculation and measurement of resulting screw pitch simply did not make sense, until it was suggested that the OP actually did a physical tooth count of the gears in the chain. His gear marked 45 actually had 54 teeth. The clue came from his throwaway remark that the blank had the number 60 cast into it

As for supply of these hard to find gears, Pete Rimmer, who did input earlier to this discussion, let it be known he had some spares available, problem solved I think.

Best wishes and stay well yourself

Brian

David, treat yourself to Brian's book, crammed with information . A 'must have' for the Super 7 owner in my opinion.

Adrian.

So I have sourced said gears and successfully cut some threads.

Many thanks to Pete Rimmer for supplying same.

One question..

16mm metric seems to be omitted from the chart posted here.

Is this an oversight or will it not fall within the tolerances..?

Did you mean 1.6mm pitch? Roderick Jenkins' table shows 0.8mm with the box set to 44 so setting to 22 should get you to 1.6mm.

If you look at Rod's chart for use with the 33/34 gears he gives the gears for M14 which has the same 2.0mm pitch as M16 (both in coarse series) so just use that. Probably just an omission as M16 is more common than M14

Edited By JasonB on 14/12/2021 18:49:34

^^^^^^^

Yes that worked perfectly.

Thank you.

Having recently fitted a Mk1 gearbox to my S7, I’m now looking for a suitable gear to allow me to cut occasional metric threads. I believe that a 17/30 tooth compound gear is required, but not available commercially. I see that at least one poster (Simon Williams) possibly had a source of this particular gear. Can anyone point me in the direction of a likely source please? TIA

One reason why a 17/34 might be hard to find is the 17t gear minor diameter is going to be very close to the hole size for a standard pin it might even be smaller. I can't check it out right now until I get home. You might be better off going with a 34/60 pairing which is the same ratio but a much stronger gear.

My "source" is making them myself. If you're interested drop me a PM and I'll explain further.

For the record here's a picture of the last batch I made

The one on the right is the 17/30 tooth pair.

HTH Simon