Myford ML7 safe spindle speed

[Michael GilliganParticipant @michaelgilligan61133]

Posted by MICHAEL WILLIAMS on 16/10/2012 11:43:20:

Now tell me what it is and why it is suitable . In fact why not tell us all how to design a plain bearing and choose appropriate materials from the bottom up . Don't omit all the lubrication considerations .

 

I cannot … and never claimed to be able to.

MichaelG.

 

[added text following the ellipsis]

 

Edited By Michael Gilligan on 16/10/2012 11:59:44

[Jolyon de FossardParticipant @jolyondefossard98326]

I saw this on Tony's wonderful site lathes.co.uk

http://www.lathes.co.uk/myfordtrileva/img8.jpg

It shows a speed of 1280 rpm is possible for the ML7.

Yrs,

Jolly

[AndyfParticipant @andyf]

The expression "white metal" seems to cover a multitude of alloys. Even "Babbitt" as used for bearings seems to have been formulated to various recipies over the years.

All I really can add to this discussion is that some sort of "white metal" was (and may still be) used for big end bearings on i/c engines, including car engines running at rather more rpm than the spindles on Myford lathes while (I imagine) being subjected to rather more stress, if only from the hammering given to them by the pistons.

Andy

[TendorParticipant @tendor]

Just a note of caution….before running a lathe at high speed, check that maximum allowable speed of your chucks. (Of course high speed = small collet chuck or similar, but worth saying, just in case.)
Rod.

[Andrew Moyes 1Participant @andrewmoyes1]

Posted by Jolyon de Fossard on 16/10/2012 23:23:53:

I saw this on Tony's wonderful site lathes.co.uk

http://www.lathes.co.uk/myfordtrileva/img8.jpg

It shows a speed of 1280 rpm is possible for the ML7.

Jolly

That's using the Myford two speed motor to which I referred earlier. I haven't heard of any incidents of problems with Tri-Leva lathes so fitted, hence the choice of a 2800 rpm motor and speed controller which does the same thing only using modern technology.

Regarding safety of chucks, if the same chuck is suitable for a Super 7 with a top speed of 2100 rpm then it is obviously OK in this application too.

Andrew M

[Terence Yates 1Participant @terenceyates1]

My ML7 Tri-Leva with the 2 speed motor does 1280 according to it's speed plate.

The motors used with the invertors are 1450 rpm and the 200% fequency used doubles the speed of the motor to 2800 rpm.

Terry.

[Jolyon de FossardParticipant @jolyondefossard98326]

Hi Terry,

Do you run your ML7 at that speed occasionally ?

Yours,

Jolly

[Terence Yates 1Participant @terenceyates1]

Hi Jolly, I do run at 1280 rpm now and then. There has never been any problem, I just oil the layshaft bearings and turn up the drip feed oilers a little.

Terry.

[Jolyon de FossardParticipant @jolyondefossard98326]

Fantastic news ! Thank you.

I have an inverter on my Colchester Student so will probably install one on the Myford as opposed to tracking down a Tri-Leva and a two speed motor.

The Tri-Leva does look nice though.

Jolly

[Richard PrenticeParticipant @richardprentice15994]

Hi expert Myford types, I am very new to Myford ownership, and am probably the worlds least good metal turner. I live near Nottingham, and don't know anyone else with one. I mostly use my lathe to make nuts and bolts and spacers etc for my motorbikes. I've had a very short bed non screwcutting lathe for some 20 years or more of unknown make or origin, but it has a 3mt tailstock and a 4" chuck. I think the polite term for me is self taught, badly.

I now also have (kept the old lathe too) a 1955 M7 that seems in pretty good condition that I want to ask about. Mine has a Dewhurst type switch, that does forward-off-forward ie no backwards. It also has V belts, running from a single phase 1/2 HP motor with a 2" motor pulley, giving exactly 500 rpm as max speed at the chuck. The oilers on the spindle are the see through Adams type, and seem to work fine unless I forget to close them when they will empty overnight.

Having been used the other lathe the Myford seems a bit underpowered, and although the belts don't slip, it's quite easy to stall the chuck on anything but a very small cut. Most of the things I make are stainless, and hardness seems to vary a fair bit. I am using indexable tools on a Myford quick release tool post. The moderately slow top speed makes a good fine finish hard to get in my humble opinion.

I'd like to up the motor HP and I now have a 1 1/2 HP (don't laugh I was going to put a 2HP on) Italian motor that is brand new, running at 1429 rpm and 4 pole so I am able to wire it to forward/reverse which I think would be handy. I have not fitted it yet. The output shaft of this motor is keyed (8mm) with a 24mm diameter. The original motor is 5/8" and therefore I propose to up the motor pulley to 2 1/2 inches to give a bit higher top speed, the bigger motor will produce rather more torque.

I've ordered a new 2 1/2" pulley but it is 3/4" bore so I will open it up to 24mm. I don't have a broaching set and they seem a bit dear for a single use at this time so I propose to use the grub screw provided and see how it feels.

If I don't like the bored pulley I will make one from scratch from some 2 1/2" aluminium stock I have. I am quite brave and like a degree of experimentation so I have also ordered a 125mm 4 jaw self centering chuck as there are some items (like the 2 1/2" pulley blank) that won't fit in the standard 3" Myford PB chuck I have.

So if you have read this far without falling asleep, can anyone tell me if my proposals seem plausible, and let me know if there's anyone in my part of the world who has one of these lovely machines too? I am planning to have a day down at Chrystal Palace later this month for a look see.

Thank you

[Ian S CParticipant @iansc]

I read somewhere that 3/4HP was about the maximum recommended motor power for the Myford. My somewhat larger lathe with 1 1/2HP will easily take .250" depth of cut, but even quarter that on my mates ML 7 scares me a bit, that lathe has a 3ph 3/4HP motor.

Ian S C

[Neil WyattModerator @neilwyatt]

Have you ever seen South Bend's 'How to Run A Lathe' manual?

There's a picture of an old-style lathe of about 6" centre height. The operator has a knee-high pile in front of him of swarf that is clearly about 3/4" wide, with a big ribbon hanging down from the work!

Neil

[BikepeteParticipant @bikepete]

"I've ordered a new 2 1/2" pulley but it is 3/4" bore so I will open it up to 24mm. I don't have a broaching set and they seem a bit dear for a single use at this time so I propose to use the grub screw provided and see how it feels."

 

Presumably this would be for the keyway? You can do that in the lathe, too, no expensive broaches needed… see e.g.

 

 

Edited By Bikepete on 02/01/2015 12:18:42

Edited By Bikepete on 02/01/2015 12:19:12

[Richard PrenticeParticipant @richardprentice15994]

Thank you for the posts, I found the book at

campkahler.com/files/How_to_Run_a_Lathe_SB_1of2.pdf

so I have downloaded it and it does look like great bedtime reading.

I realise that the Myford recommendation of max power is somewhat low, at 3/4 HP but I think that Myford were probably girls. There's evidence on the net of users upping (sometimes doubling) both motor power (and indeed spindle speeds) without problems, and I don't want to take huge cuts, I just think a bit more grunt would be useful and quite interesting. The weak points looks like the single Vee belts and the main spindle bushes. The Myford lathe castings are better than a lot of the far eastern lathes I have seen, and so I think I will give it a go and report back. Now I play the waiting game with the postman and the pulley….

When I make something I often make it twice, first with an error or two like putting a thread on a part that then needs to be put back in the chuck the other way round to finish the opposite end, instead of cutting the thread last. I don't suppose I am the only person to do that.

These model engineers are nothing if not cunning, and the tips on this website, and the old school books and even some hints and explanations from my friend the retired precision engineer who won't touch a lathe now since he nearly died of a lung infection caused by working with suds infected with bacteria, explain a lot and make the engineering very satisfying. One question comes to mind is how do most people live their lives without a lathe? I can't imagine not having one. I have a Myford vertical slide on a spare cross slide and will attempt milling a flat on some round bar on the Myford when the motor is uprated too.

[roy entwistleParticipant @royentwistle24699]

Richard beware running in reverse The screw on chuck can unscrew Also note that the Dewhurst switch should NOT be used to start the lathe it is only designed to reverse direction

Roy

[Richard PrenticeParticipant @richardprentice15994]

Thank you Bikepete, I watched the video and that seems perfectly do-able so I will give this technique a go. I have a suitable bar, but may need some 8mm square tool steel to make the cutter……..Ebay again!

Another question on Myfords, so far as I can see the Super 7 tailstock will fit on a ML7 with the advantage of being self ejecting. Currently I have a piece of 10mm round brass bar with a 40mm x 50mm round slug of brass threaded onto the back end to act like a slide hammer which I use to eject drills chucks and centres from the tailstock. Is it worth acquiring the later chuck or shall I not bother?

[Mike BondarczukParticipant @mikebondarczuk27171]

Hi Richard,

Just a comment on the speeds for a Myford, I have a Tri-Leva with the two speed motor which shows a maximum speed of 1280 rpm and I also have another motor, which originally came with the lathe which runs at 2800 rpm and the lathe is working perfectly well with either motor fitted. In answer to your question regarding the Super 7 tail stock I have just fitted one to the Tri-Leva and everything is OK with the auto-eject being a very useful feature. You will just have to slacken off the two "jib strip" screws to ensure that the tail stock will slide into the bed and then you can adjust them to suit and lock them in position, which takes about 2 minutes.

With best regards,

Mike

[Richard PrenticeParticipant @richardprentice15994]

That's just as I thought, but I am grateful for the confirmation. I remembered that I have a nice rev counter meter, and dug it out and was a bit surprised that 500 rpm was the current max speed, as it seems low, maybe OK for brass and aluminium but not so good for hard stainless. I thought it was due to the old HSS tools I was using but it's the same with sharp indexables set to correct height etc. What are your views on a beefier motor? Now to find a Super 7 tail stock……my old lathe is self ejecting and I miss it. Meanwhile I have ordered some 8mm square tool steel to make the broach tool. This forum stuff is way cool!

[Gordon WParticipant @gordonw]

I don't understand this. 500 RPM ? need to change the belts. Ally and brass need higher speeds, not lower. The V belts will handle the power ,no bother. How does the type of tool affect the speed ? Are you into fishing?

[Richard PrenticeParticipant @richardprentice15994]

Sorry if it wasn't clear, the finish is what I am hoping to improve by upping the motor pulley from 2" to 2 1/2" and thereby increasing the maximum speed a bit. I sometimes have a final finish that looks like the grooves on a vinyl record (I remember them) so I have used a broad tipped tool to lightly skim the surface at 90 degrees to obtain a finer finish, and fine wet and dry used dry, then a fine scotchbrite pad. I see that top speeds around from 600 to 800+ rpm are usual for most users. I wondered if the motor was running slow, but the motor shaft clocks at 1400.

I am learning to be more patient when cutting nearer the final cuts, moving the tool slowly and with shallower cuts which seems better for final size and finish. I think at first I was simply traversing too quickly.

My old short bed lathe only has a single Vee belt and that seems to handle it's power fine. It has a multi sized pulley on the motor shaft and on the main spindle, and the belt is longer so I can use say the smallest pulley on the motor and the biggest on the spindle with the belt crossing over, (I have even put the belt on in a figure of eight to reverse the chuck direction too on occasion) so I get a lot more speed choice than on the Myford. The tension is done by the weight of the under-slung motor. I'd put a photo of it here to see if anyone knows what it is but as yet I have not worked out how to do that, I tried pasting a low res photo of it on here but there were still too many bytes. I need to read how to do it I think there is a guide on here somewhere.

I have ordered a piece of 8mm square tool steel now ready for the broaching of the motor key way.

I seem to be into finishing, alas not fishing. Incidentally, I did buy a copy of the Ian Bradley book but found the printing quality a bit poor and the illustrations hard to understand, as if it had been reprinted rather too many times. Thank you everyone for the help. It must be tiresome dealing with my stupid questions.

[BikepeteParticipant @bikepete]

Can't speak for others but IMO not stupid at all – nice thing is you're being responsive and giving further info etc. as people make suggestions and queries. Much better than the sort of questioner who poses a question – then 20 answers later still hasn't got back to the people who responded…

[Ian S CParticipant @iansc]

Richard, Neil has just up dated the instructions for inserting photos. It's not too hard, even I managed to work out how.

Ian S C

[Richard PrenticeParticipant @richardprentice15994]

Aha! Thank you Mr. Ian, I think I know how it works now.

If so this should be a photo of the unknown old friend of a lathe I'd like to know the make of

and this is my Myford when I got it I think maybe what I called the Dewhurst switch before, isn't one.

and this is my assembled kit to do the new motor pulley, consisting of the pulley to bore from 3/4" to 24mm , a scrap bit of 24mm round bar to try in, a 24mm drill and the tool I have made being some more scrap bar with a 22.5mm piece of HSS 8mm square held in a 11.5mm hole by an 8mm grubscrew. My biggest reamer is only 21mm so I may see if a friend has a 24mm as he does stuff of those really big steam traction engines so everything he has is big. That is a job for tomorrow.

and the tool

Thanks for looking!

[JonParticipant @jon]

Mine was the white tin bearings then made a pair out of phosphor bronze.

The hard part is scraping them in, take off one area at front have to take off rear as well. Cut oil grooves In top and bottom like originals and fit a big oil pot. Just check caps for heat build up.

Used to run a Brooke Compton 1hp on mine with pulley dia 4 1/4", it transformed it in to something usable. Downside is used to get warm after 20 mins, on/off 1 1/2hrs would seize or spindle slow. Slacken caps off revolve spindle and nip caps back up, jobs a goodun again. For those that think 1 1/2hrs you would be right but how much could you do in that time running at standard revs, my guess 8 times less or 14hrs to do what I did in 1 1/2hrs with better finish.

[Richard PrenticeParticipant @richardprentice15994]

To update you guys, I bored the pulley I bought from RGD with the 3/4" bore out to 24mm bore but I felt it left insufficient metal so I decided to make a pulley from the aluminium that is shown in the chuck of the old lathe picture above.

I drilled it a little undersize and I borrowed an adjustable reamer from my friend Graham to make it an interference fit, and cut the keyway as shown in Pete's You Tube video link. This took about 40 passes! I then drilled and tapped an M8 grubscrew thread. I have left it chunky as I can't see any advantage in cutting it down or making it thinner. I did think some sexy grooves would look nice but serve no purpose. I may see what it looks like on the motor shaft when it is lined up with the layshaft pulley.

The Vee groove itself was made with a parting tool, first the deepest bit then the sides to 40 degrees. I got the dimensions from the web. I've tried an A size Vee belt in and it was a good snug fit the flat top of the belt level with the top of the pulley, and it runs true..

So I have listened to at least some of the advice here and the project is now underway….. thanks again! The money saved not buying a broaching bar I propose to squander at the Chrystal Palace show.

 

 

Edited By Richard Prentice on 04/01/2015 18:50:38

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