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ML7-R tumbler gears

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Michael Gilligan18/03/2019 08:04:57
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Posted by Hopper on 18/03/2019 02:55:25:

Later tumbler gears appear to be made from red Delrin or similar rather than the now generally obsolete Tufnol. Might be worth getting the modern gears/material.

.

I have no personal experience of the red ones ... but I remember that JS expressed an opinion:

**LINK**

https://www.model-engineer.co.uk/forums/postings.asp?th=97363

MichaelG.

Hopper18/03/2019 08:22:38
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Goodness. They do seem to have s high attrition rate across the board. Perhaps old fashioned steel would be more durable.

ega18/03/2019 12:33:10
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Posted by Michael Gilligan on 18/03/2019 08:04:57:
Posted by Hopper on 18/03/2019 02:55:25:

Later tumbler gears appear to be made from red Delrin or similar rather than the now generally obsolete Tufnol. Might be worth getting the modern gears/material.

.

I have no personal experience of the red ones ... but I remember that JS expressed an opinion:

**LINK**

https://www.model-engineer.co.uk/forums/postings.asp?th=97363

MichaelG.

Anything would be preferable to putty or "crapola"!

Mike Poole18/03/2019 13:47:10
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I don’t think there is any protection for the leadscrew drive train apart from the Tufnol gears. Should disaster occur the Tufnol gears are sacrificed and any debris should not harm the other iron gears but that is unlikely as you will probably lose drive once the gears have shed their teeth. Something more expensive that the Tufnol gears is going to break if they are replaced with steel or cast iron versions.

Mike

Edited By Mike Poole on 18/03/2019 13:47:43

Brian Wood18/03/2019 14:17:22
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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 Trice18/03/2019 15:14:29
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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 B18/03/2019 20:28:41
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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 Gilligan18/03/2019 20:46:36
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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 Dayman18/03/2019 21:22:01
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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 218/03/2019 22:48:42
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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

Hopper18/03/2019 23:34:01
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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 Gilligan18/03/2019 23:55:43
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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.

Hopper19/03/2019 00:00:15
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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 Gilligan19/03/2019 00:01:08
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Posted by Hopper on 19/03/2019 00:00:15:

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

yes

Hopper19/03/2019 03:32:25
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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 219/03/2019 07:24:45
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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 Wood19/03/2019 08:45:28
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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 Poole19/03/2019 08:49:36
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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

Hopper19/03/2019 08:53:58
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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 yet19/03/2019 10:48:34
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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.

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