ML7-R tumbler gears

[Brian WoodParticipant @brianwood45127]

Mike,

I can confirm there is no provision for a shear pin or other such protection on Myford lathes, having owned an ML4 and two ML7 versions for over more than 50 years.

Genuine Myford Tufnol gears were made from very fine grained fabric, you need a lens to see the weave, and they are a dark brown in colour. Up till now I have never seen red Delrin, which of course will have no evidence of a woven construction

Brian

[Chris TriceParticipant @christrice43267]

There's a couple of decent second hand ones on eBay as we speak. I think I have a pair of good ones somewhere.

[Mark BParticipant @markb43031]

I contacted "Myford" who run the myford.co.uk website and they didn't really answer my question about where they thought my crumbly gears came from. They just stated "They are made like this so if your machine jams these sheer off instead of destroying the full drive train". An inconclusive and non-committal answer so I'll let you make your own conclusions here.

I did however get a better response from Steve Holder of Home and Workshop Machinery. He stated that he had come across this before, but said his stock was genuine Myford old stock. I've placed an order for these parts so I'll report back on what the difference is.

I'd conclude by saying that there are some poor quality Myford branded spares out there…

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Mark B on 18/03/2019 20:28:41:

I contacted "Myford" who run the myford.co.uk website and they didn't really answer my question about where they thought my crumbly gears came from. They just stated "They are made like this so if your machine jams these sheer off instead of destroying the full drive train". An inconclusive and non-committal answer so I'll let you make your own conclusions here.

.

Thanks for the update, Mark

My conclusions [be they right or wrong] are drawn.

MichaelG.

[Jeff DaymanParticipant @jeffdayman43397]

I'd accept that "sacrificial to protect the other parts of the drivetrain" answer only if replacement gears were available from the lathe supplier in bags of 20 for a few pounds.

Not OK to keep flogging gears made of iffy weave tufnol (hasn't been the best choice of material for gears since about 1965).

Just my opinion, your mileage may vary.

[Robert Atkinson 2Participant @robertatkinson2]

The broken gears do seem to be made from rod or tube rolled material rather than sheet so will have weaker teeth.

A couple of people have rubbished "Tufnol" however Tufnol is the manufacturer not the product. They make a wide range of materials, but we are talking about laminated phenolic resin materials. Within this product there are paper and fabric types. What most people call Tufnol is the fabric material. Even then there are different grades. The classic ones are Carp, Vole, Whale and Crow. Carp is the premium fine weave material. It has excellent properties and is frquently used in aerospace, both on aircraft and even more for jigs and fixtures.
Don't compare cheap imported material with a premium British product.

Robert G8RPI.

Edited By Robert Atkinson 2 on 18/03/2019 22:49:40

[HopperParticipant @hopper]

And yet my 1937 Drummond and 1957 ML7 have survived thus far without "weak link" gears in the train. So not sure how absolutely necessary these weak link fibre gears are.

Have to wonder if their real purpose was to reduce noise and wear as those two particular gears and their mates do thrash around at the highest speed in the entire train and the metal ones on the ML7 are a bit noisy and seem to be worn more than most other gears in the train that run slower.

And the Myfrod does have a drive pin between the two halves of the leadscrew so if the makers wanted a "weak link" it would have been cheaper to put a hollow brass pin there. Or even a brass woodruff key on the leadscrew for the drive gear. Myford seem to have usually opted for the cheapest options on these lathes so you have to wonder.

 

Edited By Hopper on 18/03/2019 23:59:26

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Hopper on 18/03/2019 23:34:01:

And yet my 1937 Drummond and 1957 ML7 have survived thus far without "weak link" gears in the train. So not sure how absolutely necessary these fibre gears are.

.

Good point, Hopper

In fact, I'm not even sure that Myford [Beeston] even claimed that they were an intentional "weak link" … I suspect that, in common with many automotive applications, they were introduced for the sake of quiet running.

[ further research required ]

MichaelG.

[HopperParticipant @hopper]

You read my mind. Simultaneous typing on my edit there! See above.

No way to tell what the designers at Beeston were thinking all those years ago I suppose.

Edited By Hopper on 19/03/2019 00:05:46

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Hopper on 19/03/2019 00:00:15:

You read my mind. Simultaneous typing on my edit there!

[HopperParticipant @hopper]

Quiet running makes sense on the Super 7/ML7R with their top spindle speed of over 2,000rpm, double that of the grey porridge ML7. I would not like to listen to the metal gears on my ML7 at that kind of speed.

Plus, if the Tufnol gear were for a "weak link" effect, they would have only fitted one and not two, you would think.

Edited By Hopper on 19/03/2019 03:33:31

[Robert Atkinson 2Participant @robertatkinson2]

Posted by Hopper on 19/03/2019 03:32:25:

<SNIP>.

Plus, if the Tufnol gear were for a "weak link" effect, they would have only fitted one and not two, you would think.

Edited By Hopper on 19/03/2019 03:33:31

Not for production, that would be two part numbers for otherwise identical parts to make, stock and keep track of. That is extra cost. And the SRBF gear is probably cheaper anyway. But like so many of these things only the original designer knows the real reason. I've certainly designed things where you would not be able to guess why I chose a part.

Robert G8RPI

[Brian WoodParticipant @brianwood45127]

Hello Hopper,

You stated that there is a sheer pin in the two part leadscrew on Myford lathes. I have the ML7R with gearbox, the leadscrew is a one piece shaft, no coupling. My previous ML7. without a gearbox, was also a one piece leadscrew shaft, as was the ML4 before it which I inherited from my father.

So, from my experience, it is not 'one size fits all' situation.

It would make a lot of sense

Regards

Brian

[Mike PooleParticipant @mikepoole82104]

On the ML1-4 the gears drove through a small pin but the 7 series use a key, if the designers did not intend the Tufnol gears to be the drive train protection then they made a basic error in not fitting any other form of protection. If they fitted them for quiet running it was very considerate of them. Mine spend most of their life in neutral and only get used for long feeds or screw cutting. They are now very expensive gears but was Tufnol a cheap material in 1947? I suspect as it was much more widely used then and was relatively cheap. Meddings also went fo Tufnol gears probably for quiet running but these are vulnerable to damage by changing gear with the machine running. I suspect that Tufnol gears cost is high partly because of material but also tooling as Tufnol is one of those materials that takes the edge off a cutter in no time.

Mike

[HopperParticipant @hopper]

True. I was thinking of my 1957 ML7 with no gearbox that has the piece on the left end of the leadscrew that slips over the leadscrew end and is held with a dowel pin going through the two.

[not done it yetParticipant @notdoneityet]

Change wheel gears have even been 3D printed.

Aluminium gears might be an intermediary step between tufnol and steel. Even brass?

I believe Ford engines in the Zephyr/Zodiac had a tufnol oil pump drive. They eventually changed the design or changed the engine.

My lathe has tufnol tumblers. One got damaged when moving the lathe but they still function perfectly well. I will change to aluminium if/when they fail.

[Mark BParticipant @markb43031]

I just wanted to report back having got a pair of tumbler gears from Home Workshop and Machinery. Having compared the NOS Myford ones they are certainly different in the grain of the material isn't radial. I fitted them and all I can say is that they just work. No tight depthing of the gears, it runs nice and smooth.

The fake Myford ones which fell apart didn't depth correctly. Having measured the 28 tooth wheel, it was 0.3mm bigger across the wheel which wouldn't help matters.

So I guess you just make sure the parts you get are really original Myford. Hard when you are faced with Myford branded.

Anyway, problem solved so thanks for all the pointers.

[Michael GilliganParticipant @michaelgilligan61133]

Thanks for the 'closure' Mark

MichaelG.

[Steamer1915Participant @steamer1915]

Social distancing in the workshop gave me the opportunity to make a batch of these gears.

More pictures in the album showing the process.

Material is Tufnol Whale brand.

DP is 20

Pressure angle is 20 degrees

OD 30T = 1.600" 28T = 1.500"

Very pleased with the results.

Best regards,

Steve.

Edited By Steamer1915 on 19/04/2020 11:31:41

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