Availability of a T33 & T34 Myford Change Gears?

[David CoulingParticipant @davidcouling56621]

Hi Guys,

I know this question has been posted previously but with the passage of time, my hope is the situation may have changed and maybe someone can suggest where I can purchase a pair of T33 & T34 change gears for a Myford MLSuper 7?

Many thanks….David

[David CoulingParticipant @davidcouling56621]

Myford Change Gears

[William SParticipant @williams]

I got my 2 from the “new Myford” at Ali Pali ME exhibition a couple of years ago, so check there website.

Have you found the comprehensive chart of most combinations on the other post about this topic? I think it is on the second page, it’s the best thing I think I have found! The few times I have needed this mod it has been for some really odd stuff that would not otherwise be possible.

Hope that helps

William

[old martParticipant @oldmart]

Looking on ebay regularly under metalwork lathes, I see a large number of Myford gears of all sizes always on sale.

[DC31kParticipant @dc31k]

Posted by old mart on 05/06/2021 20:08:39:

…a large number of Myford gears of all sizes always on sale.

Unfortunately, he is not looking for a "large number" "of all sizes". He is looking for one gear in each of two specific sizes, 33t and 34t.

Could you point us to a specific eBay seller who currently, or within the last three months, has or had one or both of these in stock. Thanks.

If the OP does not want to cut his own gear, another option might be a 3D printed one. Have a look on Thingiverse as one might exist already, or there will be a program there to produce the file to enable it to be printed.

A second option is to approach an eBay seller, you_engraving. He makes Colchester and Harrison gears in delrin at good prices, and might make you a Myford one.

[Pete RimmerParticipant @peterimmer30576]

I did a batch of 33 and 34T for the myford about a year ago when they were unavailable. I have some still sitting on the shelf if you can't find them elsewhere.

[David CoulingParticipant @davidcouling56621]

Wow….thanks for all of your replies guys. I have searched the various sellers of gears on ebay and not surprisingly these two gears are the ones which are not available.

Pete….I would very much like to take you up on your offer…is it possible for you to PM me please.

Many thanks for all of your inputs…

Cheers

David

[Peter SansomParticipant @petersansom44767]

RDG periodically have stock. I you contact them they will let you know when they are expecting more.

Peter

[david homerParticipant @davidhomer12226]

HPC gears are good source of spur gears, not cheap though. I think Myford gears are 20dp or used to be on earlier lathes.You will have to modify the bore to suit your needs they do 33 and 34 tooth.

David

[Roderick JenkinsParticipant @roderickjenkins93242]

Myford change gears are 14.5 degrees pressure angle. Unfortunately HPC only do 20 degrees.

Rod

[Frank MckenzieParticipant @frankmckenzie32989]

So I've got an imperial super 7 with a quick change gearbox and am looking to cut metric threads.

Is it just a matter of changing to 33t gear..or is there more to it than that..?

[Tony Pratt 1Participant @tonypratt1]

Posted by Frank Mckenzie on 15/11/2021 14:22:09:

So I've got an imperial super 7 with a quick change gearbox and am looking to cut metric threads.

Is it just a matter of changing to 33t gear..or is there more to it than that..?

Off the top of my head you can get a very close approximation using 33 & 34 teeth gears, quite a few posts on here already about it & I did have both gears but my Super 7 has now gone to another home along with the gears.I'm sure others will chip in in due course

Tony

[SteviegtrParticipant @steviegtr]

I bought mine around 18 months ago from Myford/ RDG. I think they are out of stock as Kev is making some now. Look him up. Youtube. Mr Factotums workshop.

Steve.

[Simon Williams 3Participant @simonwilliams3]

Reverting to Frank's question "is there more to it than that", well, yes there is.

I did a search on this forum and came up with this as being pretty typical of the collected knowledge:

33 &34 T gears

It includes a useful table courtesy of Roderick Jenkins (first page of this thread) detailing what to set the QCGB to for a wide section of metric pitches.

There are other references, also the definitive text is Brian Wood's book "Gearing of Lathes for Screwcutting". Amazon say they have stock.

Please note you need to know if you have an early gearbox or a late gearbox. This thread :

Myford S7 metric threads

explains why, and how to tell the difference.

HTH Simon

[Simon Williams 3Participant @simonwilliams3]

Dunno if it helps, but this thread has got some further information about the 33 and 34 tooth gears:

More details

HTH Simon

[JESParticipant @jes]

How about 3d Printing?

JES

[Frank MckenzieParticipant @frankmckenzie32989]

Thanks for all the replies.Very helpful indeed.

I don't know about the type of model gearbox early/late.

The lathe itself is 1974-1977ish according to the serial number.

Is there any way of knowing the gearbox vintage..?

[Tony Pratt 1Participant @tonypratt1]

Posted by JES on 16/11/2021 09:17:28:

How about 3d Printing?

JES

Unlikely to be strong enough?

Tony

[Simon Williams 3Participant @simonwilliams3]

Diagnosing the gearbox vintage is straightforward. There are pictures of the differences in the threads referenced above, but the simple way is to first check that the thread cut is that indicated on the gearbox top label. So check – for example – if the levers are set for 20 TPI then 20 TPI is what you get.

Now open the gear cover to look at the changewheels carrying the drive down to the fat 72 T gear on the input shaft of the gearbox. If the gearbox is the later type the input gear on the mandrel (first stud below the tumbler gears) will be 24 tooth. It will be mounted on a 30 T which meshes with the tumbler gears. I don't have a picture of this to hand but maybe someone else can add one. There are pictures in the threads referenced above.

If the gearbox is the older type the gear driving the chain down to the input to the gearbox will be a 12/30 compound gear as the old gearbox runs at half the speed of the newer one. Here's a picture of the gear cluster for the older gearbox:

The Myford one is the steel one on the left; the bronze one on the right is another (related) story.

If you do have the older gearbox don't buy the 33 and 34 T gears – they are no use to you. If this is the case report back on here and I will introduce you to the alternative solution (it's that bronze gear!).

Best rgds Simon

xxx

[KWILParticipant @kwil]

Posted by Frank Mckenzie on 16/11/2021 10:24:07:

Thanks for all the replies.Very helpful indeed.

I don't know about the type of model gearbox early/late.

The lathe itself is 1974-1977ish according to the serial number.

Is there any way of knowing the gearbox vintage..?

Later model from QC2495 onwards (1956). Look it all up on Lathes.co.uk if you want more info.

[Brian WoodParticipant @brianwood45127]

Frank,

There are three clues.

The easiest being to look at the gearbox, right hand side. The later ones ( Serial 2501 + onwards) have the leadscrew running straight into the box. The earlier versions had a little housing on the right hand side into which the leadscrew went instead. The gearbox serial number is stamped on that side.

Another clue is the one Simon Williams mentioned with 30/12 tooth gearing in the gear chain. This was to provide a 1:2 reduction before feed to the early gearbox. Later boxes incorporate reduction gearing of 26/52 hidden behind the mounting plate that the banjo fits over; there is a small teardrop shaped window where you can see part of the 52 tooth gear. In the later gearbox the leadscrew is brought right through the gearbox to those reduction gears.

From the date of the lathe I suspect yours is the later version gearbox in which case the table that Roderick Jenkins provides will apply, as will the material in my book

Finally, there is a simple replacement for the lower clamp stud for the banjo that allows it to be lowered, which then makes room for mandrel gears in excess of 34 tooth to be used as drivers, thus opening up a whole world of possibilities in screwcutting.

Regards Brian .

Edit   While I've been composing my input, Simon has answered you query, as has KWIL and if you have the early gearbox, then Simon is the man to help you. He did a LOT of work along with the late John Stevenson to get around the calculated gearing values based on versions of 33 and 34 gears having 33.5 teeth and 34.5 teeth!

Impossible of course but there are ways and means! 

Edited By Brian Wood on 16/11/2021 11:44:12

Edited By Brian Wood on 16/11/2021 11:45:00

[Frank MckenzieParticipant @frankmckenzie32989]

Great information there gentlemen.Thank you.

Yes it is indeed the later model I have.

All indicators for such are present.

[Simon Williams 3Participant @simonwilliams3]

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

[Brian WoodParticipant @brianwood45127]

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

[Adrian 2Participant @adrian2]

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

Adrian.

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