What motor pulley size for ML1 Lathe?

[Chris VParticipant @chrisv]

I have an electric motor 1425 RPM on the plate. An 8" dia flat belt pulley on the Myford bench top motor stand/counter shaft. Then flat belt pulleys from this to the 1930's ML1 that I am trying to resurrect and get going.

Looks like I will need to make a flat belt pulley for the motor, advise on what size should it be please? (I don't wish to change to vee belts).

Any reason the pulley should not be made of brass?

Thanks in advance.

[Chris VParticipant @chrisv]

[Michael GilliganParticipant @michaelgilligan61133]

I suggest you make the motor pulley ‘poly-vee’

Then just run it flat on the lathe.

MichaelG.

[Pete RimmerParticipant @peterimmer30576]

Michael makes a great suggestion. Poly-vee belts run very well on flat pulleys and you need a surprisingly small one to get the same traction as a larger flat belt. Some south bend lathes even run a vee belt on the flat pulley as standard.

[Chris VParticipant @chrisv]

Thanks Michael, having just bought the 8" Myford FLAT belt pulley I wish to use a flat belt between it and the motor.

Its the size Id like guidance on and can I use brass if I choose to?

I appreciate a vee belt system is likely easier to set up but i'm looking to set the lathe up nearer to the original look.

Cheers.

[Michael GilliganParticipant @michaelgilligan61133]

Sorry to hear that you have already made the purchase, Chris

A poly-vee would run very effectively on the lathe’s original flat-belt pulley

Millions of Tumble Driers effectively use this arrangement …

MichaelG.

Edited By Michael Gilligan on 04/10/2019 12:05:51

[Chris VParticipant @chrisv]

Hi Michael & Pete, thanks for that.

Ok, I have a vee pulley for the motor already + new to me old 8" flat belt pulley on the countershaft.

Can I use a vee belt between them then? Sorry if i'm being dense!

But I still have no idea of what size…..

[Pete RimmerParticipant @peterimmer30576]

Yes you can. That was standard fitment on the South Bend 9 and 10 inch machines.

The countershafts used in the underdrive models followed the design of that for the 9-inch where a V-belt from the motor passed over a narrow flat pulley on the countershaft, a system confusing to modern eyes but one that works well in practice.

**LINK**

[Brian WoodParticipant @brianwood45127]

Hello Chris,

I'll try to answer your question on pulley size

You need to work back from the maximum spindle rpm, which on a lathe of that vintage with white metal bearings would have been about 600 rpm. Measure the diameters of the two stepped pulleys on countershaft and spindle that would be used for that spindle speed and call them D1 and D2 respectively.

Call the motor pulley diameter 'x', the countershaft pulley is known at 8 inches

Now we can express everything as a calculation where x = (600 x 8), multiplied by D2/D1, all divided by 1425

You should finish up with a motor pulley diameter in the region of about 1 inch or so, assuming a step up ratio D1/D2 of something like 3:1

Don't forget to include a degree of crowning on you motor pulley when you make it to keep the flat belt running in the centre.

Finally, brass will be satisfactory ( I assume you already have a chunk) but cast iron is the more traditional material

Regards

Brian

[BazyleParticipant @bazyle]

Brass will be expensive and a bit more 'slippy' than most other materials. Why not start off with a simple 2in wood pulley and see how it goes. Then you can turn it down bit as suits. Don't worry that you haven't got a working lathe to make it on, just drill for the motor spindle turn in situ but keep the dust out of the motor.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Michael Gilligan on 04/10/2019 12:03:34:

Sorry to hear that you have already made the purchase, Chris

A poly-vee would run very effectively on the lathe’s original flat-belt pulley

Millions of Tumble Driers effectively use this arrangement …

MichaelG.

.

Sorry … Slightly garbled there ^^^

I now realise that it is the 8” pulley that you have just purchased, not a belt

My text should therefore read:

A poly-vee would run very effectively on the 8” flat-belt pulley … just use poly-vee profile on the motor pulley.

.

MichaelG.

[Chris VParticipant @chrisv]

Ah ok, I can now see the way forward. I can turn either wood or brass on my wood lathe so can try as has been suggested several pulley sizes. Then assuming I stick with flat belts, source a cast iron pulley blank and turn it on the ML1 once its up and running.

Thank you all for your insights and help, much appreciated!

[SillyOldDufferModerator @sillyoldduffer]

Posted by Chris Vickers on 04/10/2019 11:37:37:

I have an electric motor 1425 RPM on the plate. An 8" dia flat belt pulley on the Myford bench top motor stand/counter shaft. Then flat belt pulleys from this to the 1930's ML1 that I am trying to resurrect and get going.

Looks like I will need to make a flat belt pulley for the motor, advise on what size should it be please? (I don't wish to change to vee belts).

Any reason the pulley should not be made of brass?

Thanks in advance.

Looking for the maximum spindle speed of an ML1, I found this thread on Practical Machinist suggesting a top speed of 900rpm for ML1 to ML4 from a 1/3HP motor. ( 900, 600 & 320 direct / 150, 100 & 54rpm from backgear ).

Rather helpfully the same thread 'Georgineer' describes an ML4 set-up with pulley sizes and a blurry photo of the counter-shaft arrangement for a 1425rpm motor. It's begging to be copied!

Dave

[Chris VParticipant @chrisv]

THANK YOU Dave, thanks that's a great link, Cheers!

[HopperParticipant @hopper]

I think those old Myfords are like my M-type Drummond of similar vintage and will run at 800rpm top speed ok.

So you want your countershaft to be doing about 400 rpm. This gives three speeds of 200, 400 and 800 rpm with a typical set of stepped pulleys on the countershaft and lathe headstock spindle.

So to get your 1425rpm motor to spin an 8" pulley at 400rpm, motor needs a 2-1/4" pulley.

Aluminium should work fine as material too.

Plenty of belt and pulley calculators online if you want to play around with variations.

And you can buy for about $10 online a tachometer gun that reads a white paint mark on your pulley or chuck and gives a digital readout of exact rpm to check it.

Edited By Hopper on 05/10/2019 10:36:00

[Chris VParticipant @chrisv]

Thanks so much Hopper that's nice clear and simple, bit like me! I will start with a 2.5" pulley. One question, if I then did wish to play further down the line, if I reduced down in size to say 2.25" or even 2" would I end up with higher or lower lathe speeds?

Just this morning my wife joked about something to check the speed, made I larf when I read about the tachometer!

Cheers

Chris.

[Howard LewisParticipant @howardlewis46836]

The smaller the motor pulley the lower th will be the speed of the lathe mandrel.

ie 1425 rpm motor with 2" pulley driving a 8" pulley, which will run the countershaft at 1425 / 4 = 356.25 rpm, assuming no slip.

Using basic engineering maths:

To achieve Hopper's maximum speed of 800 rpm at the mandrel you would need a speed increase of 2.24 : 1.

This could be obtained by having a 4" pulley, on the countershaft, driving a 1.785 " pulley on the mandrel.

Minimum mandrel speed would be by having a 1.785" pulley on the countershaft driving a 4" pulley on the mandrel (ASSUMING THAT THERE ENOUGH ROOM ON THE HEADSTOCK FOR IT ).

If there isn't, you need to do some more simple maths to calculate the size of the Driving and Driven pulleys to achieve this ratio. Middle pulley size is merely (Driver + Driven) / 2 to get two pulley diameters that are the same.

Middle speed would be obtained by having the middle sheave of each pulley (Countershaft and mandrel ) 2.89" diameter

Since you are using flat belt drive, these diameters should be fairly easy to make.

This should provide mandrel speeds of 800, 356 and 159 rpm, using the same belt tension for each setting.

Excessive belt tension may avoid slip at the expense of the life of the bearings in the countershaft and the Headstock.

These speeds can be reduced by engaging back gear, but don't forget to release the grubscrew in the pulley on the Mandrel., to allow the pulley to run free on the mandrel while back gear is engaged. But don't forget that a pulley running on the shaft but not at the speed of the shaft, will need lubrication. So the grubscrew hole in the shaft needs to be the depth of the same diameter as the grubscrew.

For a ML1 I would think in terms of 3/16" or 1/4" BSF. Having been produced in the mid to late 30s, up until the maid / late 40s, threads will be Whit form, either BSW or BSF. The Myford ML7 made it's debut in about 1946 / 1947.

Back gear may decrease the above speeds by a factor of 4 or 5, possibly 6, giving speeds low enough, perhaps to use a tap or a die under power.

Certainly, when running at 800 rpm, you need to lubricate the mandrel bearings more frequently than when running at lower speeds. At best thee bearings will be white metal, or more likely direct in the cast iron of the Headstock, and not intended for high speeds for long periods.

Howard.

[Chris VParticipant @chrisv]

Hi Howard, many thanks for all that. I have all original pulleys now except for the motor one so will make one for that and see how I get on. I see I can buy cast iron round by the inch, might be a good intro to cutting that material before tackling the James Coombes. Thanks for all the other tips, particularly interesting one re using taps & dies under (slow) power feed.

It leads me to a further question as I only have maybe 5 gears, change wheels I think they are more properly called. Apart from using them to lathe cut threads, is the only other or at least main other use to change turning feed speeds?

I'm just wondering if I need to source and buy the missing ones right now, I don't see me cutting threads other than with tap & die for a long time, there's far too much to learn in far too little time available before then!

Cheers

Chris.

[HopperParticipant @hopper]

YOu dont need the full set of gears if you are not going to screwcut threads. For fine feed just set up the gear train using three smallest gears and three largest gears you have.

[Howard LewisParticipant @howardlewis46836]

Fairly recently helped set up a ML4, which had a full set of changewheels. I made a couple more 20T so as to provide a fine feed, and gave a spare 60T using three changewheels.

The lathe did not have tumbler reverse.

The set up was:

Mandrel 20T Stud 1 – 60/20: Stud 2 – 65/20:Leadscrew. – 60. From memory, with the 8 tpi Leadscrew this gave a feed of about 0.004" / rev.

The 20:65 on Stud 2 prevents a clash between the 20:60 mesh on the Mandrel , and the second 20:60, had it been on Stud 2.

You may need to file out the Mandrel end of the banjo, possibly just enough to take out the draft angle, to enable the gears to mesh.

To maintain backlash, I run a piece of card, about 0.003" thick into each mesh, starting at the Leadscrew / Stud 2 mesh. The banjo pivots around the Leadscrew, so this has to be the starting point. When the Mandrel / Stud 1 mesh has been set, you can tighten the 5/16 BSW setscrew that clamps the banjo.

Being an M type the gears are compounded by 3/32" pins in drillings, that only go halfway through, the Driving Collars, and gears..

So you would need to obtain some extra wheels to do this. Gears from a ML7 will fit, but need to be drilled for the pins, since they are compounded using a key for the drive. (The second 60T was ex an ML7 one. The 3/32 hole was drilled opposite the keyway )

HTH

Howard

[Chris VParticipant @chrisv]

Thanks so much again Hopper & Howard. I just had a look and I have 3x 65T, & one of each 40T, 30T, 20T, so possibly enough to get me going on a slow feed speed.

Two of these have the later key slot but as you suggest I could drill these. I'm wondering how many is a full set but that's for another day.

Slightly intrigued by the requirement to "maintain backlash", so far with regards to the cross slide Ive only learnt a little about ways to remove backlash with gib strips etc….never heard about maintaining it…Ive so much to learn!

Also wondering if someone has come up with a tap/die holder to fit on the sliding carriage ie for powered threading..along the lines of a travelling steady…?

Many thanks

Chris.

[Howard LewisParticipant @howardlewis46836]

It is important to maintain backlash in a gear train, if it is to run at speed. (In a measuring, low speed environment, backlash would be a disadvantage, and to be avoided )

If gears are run at speed without backlash, noise will certainly be generated, and the gears will wear.

From memory, the complete set of changewheels for a M type started at 20T and increased in 5 tooth increments upto 65T

On the M type, there is a driving collar on the mandrel which drives the first pinion via one of the 3/32 pins. Subsequent compounded gears are coupled in the same way. The Leadscrew carries a driving collar, which clamps, to it, like the one on the Mandrel, with a 1/4 BSF grubscrew, and again, a pin couples this to the gear.

Howard

[not done it yetParticipant @notdoneityet]

Posted by Chris Vickers on 06/10/2019 16:37:37:

Also wondering if someone has come up with a tap/die holder to fit on the sliding carriage ie for powered threading..along the lines of a travelling steady…?

Many thanks

Chris.

There are propriety (one can make one’s own, of course) sliding die holders to fit the tail stock, which also acts perfectly adequately as a sliding holder for tapping.

[Chris VParticipant @chrisv]

Many thanks again Howard.

Also thank you Not Done it Yet, yes I'm aware of those, I have one in fact.

I meant a way of holding taps & dies on the lathe fed carriage so the thread is cut under power at slow speed.

Right now this seems like a really good idea, say if you had to thread a long length of bar or tap a deep hole…but perhaps I'm wrong.

I think with the tailstock fixed the sliding holder would come apart if cutting a long thread..and would'nt hold a tap either, or am I again missing something..else (-:

Cheers

Chris.

[not done it yetParticipant @notdoneityet]

Hi Chris,

Threads can be cut with a single point tool using the carriage lead screw to set the pitch. There is no need, or point, of using the carriage feed with taps and dies. Single point cutters are cheap, easy to grind and sharpen. There are multi-point inserts available which are also used – probably more in a production environment than for us hobbyists, but available if one wishes to cut threads that way.

External threads can be cut for the full length of the carriage travel, even on small diameter rods . A travelling steady or rod guide of some description could be advantageous for anything which may flex. Internal threads are rarely required for more than the length of an appropriate boring bar with cutter.

Other means of doing the job might be to rough out the cut on the lathe and finish with a die or tap – avoids worrying about starting the thread crooked to the axis (or not perpendicular to the hole), or a way of cutting a coarse thread with a less-heavy workload while using a large diameter tap or die manually.

Yes, with tailstock fixed, a die would have limited travel – but nowt stopping one moving the tail stock at intervals.

[Author]

Posts