NewtonTesla systems

[Stephen FollowsParticipant @stephenfollows82099]

Thanks for all of the replies to my post. Excellent advice in abundance!

My ML7 has white metal bearings. Don't know if it has a hardened shaft, don't know how to tell if it is or not.

My main reason for fitting a new motor is speed. At present the maximum I can get is 680rpm. there are a few occasions that I would like 1000rpm, changing the bearings would not be a problem, not sure about the shaft.

[Stephen FollowsParticipant @stephenfollows82099]

Bearings continued. Having said it would be easy to change the bearings I have found that a matched hardened shaft and bearing kit costs £339.50. Ouch!

[Brian WoodParticipant @brianwood45127]

Hello again Stephen,

If it is just a spindle speed increase you want to achieve then an earlier posting suggesting pulley size alterations will do that for you about as cheaply as you could wish.

If though you want to get the added advantage of variable speed control, which I am sure will be a revelation, then the change to 3 phase speed control will do that as well as giving you a useful upper motor speed.

The increase gained in power by switching to a bigger capacity motor is independent of motor speed and will give you a greater machining capacity, which combined with variable speed control will give you all the control and power you are likely to need. It is perhaps a little unfortunate that the Newton Tesla system does not include a 3/4 HP motor option as I think 1 HP is really more than you need for that size of lathe.

A soft mandrel was usually fitted to Myford ML7 lathes with white metal bearings and I really believe that with attention to lubrication there is no reason why they could not stand occasional spindle speeds up to 1000 rpm or so, despite all the manufacturers warnings to the contrary. It is as Neil has observed, they would not endorse what I have just said in case of claims being made in cases of unrealistic expectations using sustained performance.

Incidentally, the soft mandrel is easy to test with a fine file on the spindle nose on the face between the chuck threads and 2 MT bore, it should bite rather than slide.

If you shipped your lathe just as it is to the USA and ran it on their power network, your 680 rpm spindle speed would immediately change to just over 800 rpm by virtue of their 60 Hz supply. I doubt the bearings would even notice the difference. The best test tools for plain shaft bearings and imminent failure are your fingertips and over warm bearings are the first signs of distress.

Again, I hope this dissertation helps you make up your mind.

Regards Brian

[Russ BParticipant @russb]

Exactly my point. The white metal bearings are no longer available, so I'd crunch a few numbers to get a feel for what's sensible, but all dependant on the oil feed, and I would consider the oil cups on the ML7 to be extremely effective. Also oils theses days have some very advanced additives so I'd expect them to outperform the kinds of oils available 70+ years ago when these were designed – by 25% maybe? I'm a long way from home so cant pull out any figures from texts but I'm sure it's in many of the old school engineering encyclopedias.

[Clive Brown 1Participant @clivebrown1]

Another point re. the choice between 1/2 and 1 hp. motors is their physical size. When replacing the 1/2 hp single phase motor on my bench mounted ME10, I couldn't fit anything larger than 3/4 hp. (0.55 kW) 3ph. without significant modification..

3ph. motors mostly seem to have a large terminal box which protrudes outside the nominal frame size. This was a problem in my case.

[JonParticipant @jon]

Oil feed is the main problem with certainly the older ML7.
Made and scraped in phosphur bronze for mine with deep galleries top and bottom. Used to get seizures around 20 mins in excess of 1000rpm and needed the top caps constantly adjusting.
Agree cant have enough power i ran 1hp Brook Crompton for years, at least you could put a menial cut on then and that 8hr job turned in to 2hrs.

Totally agree with Newton Tesla absolutely no help at all, its just supplied as kit with no help on wiring in the trips and where to, they even said the manual dont state. So bought a superior Brook Crompton motor from USC Scotland £26 cheaper than Teco, remote pod from NT £18 delivery took 2 working days! and a Mitsubishi plus EMC filter £25.5 from Inverter Drive who were exceptionally knowledgable and helpful not to mention cheaper.
Buying from 3 places worked out around £72 cheaper than one company supplying the lot with no backup.

[Tony JeffreeParticipant @tonyjeffree56510]

I fitted one of the first NT 1/2 hp systems to my ML7. I wanted to increase the speed range of the lathe, so persuaded NT to programme the VFD for a 5-120 Hz range, giving me a max speed of 2.4 times the standard spindle speeds. They advised that I should fit a hardened spindle/bronze bearings, which I did – somewhat cheaper than quoted above, because it was before Myford was sold to RDG. Having said that, the lathe (sold to me by John Stevenson) came to me with a 2 speed 3-phase motor, so John had been running it at 2x standard speeds on the original white metal bearings & unhardened spindle.

The system has worked very well for me so far – having the extended speed range greatly reduces the number of times I have to switch pulleys, which is a useful advantage.

[Fowlers FuryParticipant @fowlersfury]

I freely acknowledge an ignorance of things electric but with reference to my earlier post, Transwave told me that the motor's current consumption was a critical factor – assuming of course that the lathe's bearings were OK.

Accordingly I set the LED readout to show amps and if they get close to 2.6A (taken from the motor's data plate) then I change the belt on the pulleys to prevent the thermal cut-out operating in the middle of machining, invariably at some critical point ! Yet it seems from posts, such as Tony's above, that others don't suffer from this constraint.

On my Myford S7 to keep below the 2.6A, the motor has to be running fairly fast so when needing a slow mandrel speed I'm forever "swopping pulleys". The desk fan helps motor cooling but the set up only permits fairly small changes in motor speed via the pot at any one belt & pulley setting.

[Stephen FollowsParticipant @stephenfollows82099]

Looks like I have started an interesting topic here. Thanks again for the continued contributions.

I think I will have to abandon the idea of speeding up my lathe. The cost of new bronze bearings and hardened shaft added to fitting an invertor and three phase motor takes the price to over £700.00. £339.50 for shaft and bearings seems a bit excessive to me, (a lot excessive if I'm honest), but I cannot find any cheaper anywhere.

It's a shame but unless I can find affordable bearings etc. it will have to stay as it is!

[Brian WoodParticipant @brianwood45127]

Hello Stephen,

I don't wish to appear to be bullying you into a course of action you might be wary of, but I can really see little harm in buying a new pulley for the motor to raise the overall spindle speed by a modest amount, to say 850 rpm which would be only 30 odd rpm above that for an unmodified system running on 60 Hz supply and then see how it goes.

You will have ample warning of any bearing stress, it is only likely to manifest itself after protracted periods of running and the investment in trying it out is really very limited. If you don't like it, then revert back.

Regards Brian

[SillyOldDufferModerator @sillyoldduffer]

Posted by Stephen Follows on 06/11/2017 14:18:05:

…

I think I will have to abandon the idea of speeding up my lathe. The cost of new bronze bearings and hardened shaft added to fitting an invertor and three phase motor takes the price to over £700.00. £339.50 for shaft and bearings seems a bit excessive to me, (a lot excessive if I'm honest), but I cannot find any cheaper anywhere.

…

Rather than hot-rodding a venerable old ML7 with electric Viagra and risk having a seizure, why not spend the money on a new Chinese Lathe? Keep the Myford for Quality Work and use the Chinaman for high-speeds. I'm quite serious, LBSC had four lathes and I've often thought owning two would be a great convenience.

Dave

[Stephen FollowsParticipant @stephenfollows82099]

Another lathe is a good idea, just a matter of space.

[Russ BParticipant @russb]

Posted by Stephen Follows on 06/11/2017 21:43:56:

Another lathe is a good idea, just a matter of space.

I got a mini lathe for this reason, I removed the back guard and drip tray, and slide off tailstock and then it's not too much trouble to slide it away under my bench when not in use. I've not stripped and checked it, but it turns acceptable/good parts out of the box – I can't complain.

[Neil WyattModerator @neilwyatt]

Owning three brings a warm glow, even if one fits in a shoebox

[David Standing 1Participant @davidstanding1]

Posted by SillyOldDuffer on 06/11/2017 15:31:15:

Posted by Stephen Follows on 06/11/2017 14:18:05:

…

I think I will have to abandon the idea of speeding up my lathe. The cost of new bronze bearings and hardened shaft added to fitting an invertor and three phase motor takes the price to over £700.00. £339.50 for shaft and bearings seems a bit excessive to me, (a lot excessive if I'm honest), but I cannot find any cheaper anywhere.

…

Rather than hot-rodding a venerable old ML7 with electric Viagra and risk having a seizure, why not spend the money on a new Chinese Lathe? Keep the Myford for Quality Work and use the Chinaman for high-speeds. I'm quite serious, LBSC had four lathes and I've often thought owning two would be a great convenience.

Dave

Myford 254S plus Boxford 330 here, I can thoroughly recommend owning at least two lathes

[Andrew Moyes 1Participant @andrewmoyes1]

Apologies for joining this thread late but the following may be of interest.

When I first got my ML7 lathe in 1971, I renewed the white metal bearings and carefully scraped them to fit. The measured spindle clearance was 0.0005” using a DTI and long bar in the chuck. After 40 years’ use, the last 10 with a VFD-controlled 2,850 rpm motor and top speed of 1300 rpm, there was no measurable change in clearance.

When I first fitted the 2850 rpm motor, I ran the lathe at top speed for 1.1/2 hours to check for overheating. The bearing caps were moderately warm to the touch but nothing untoward for such a close-fitting bearing. Myford themselves were not concerned as they offered a two speed 1450/2850 rpm motor until the lathe went out of production. It could be fitted to any ML7 but was mainly aimed at Trileva fitted lathes to give instant access to six speeds instead of three. The Trileva used standard white metal bearings.

The idea that Myford introduced replacement phosphor bronze bearings because of overheating white metal bearings is definitely a myth which has unfortunately found its way onto Tony Griffiths’ excellent site and is becoming 'gospel'. I remember the Myford press release at the time which said it was due to the prohibitive cost of obtaining white metal bearings. Phosphor bronze was a cheaper alternative but it meant replacing the spindle with a hardened version as the unhardened one previously used was not compatible with bronze.

If you are buying a new three-phase motor and VFD, I don’t see the point in running a 1450 rpm motor at 100 Hz when a 2850 rpm motor can be run at 50 Hz within its manufacturer’s rating.

Assuming your bearings are correctly fitted and lubricated, and not tight, installing a 2850 rpm motor with a VFD is for me a ‘no brainer’. I certainly wouldn’t swap the lathe because of fears about the bearings.

[Michael GilliganParticipant @michaelgilligan61133]

Brilliant 'Factoid-busting' post, Andrew !!

MichaelG.

.

[*] Despite sloppy usage in more recent years .. Norman Mailer's word is very appropriate:

See my post 03/03/2015 here: http://www.model-engineer.co.uk/forums/postings.asp?th=104837&p=2

Edited By Michael Gilligan on 11/11/2017 08:19:48

[Stephen FollowsParticipant @stephenfollows82099]

REALLY CONFUSED!

I'm more uncertain now than when I began this thread. Looking at answers here and reading other websites it seems that:

a). Never run an ML7 faster than 1000rpm at the chuck on pain of destroying the machine unless bearings are upgraded.

b). Run it at up to 2000rpm for hours on end with white metal bearings and don't listen to the doomsayers.

c). Pick an option somewhere in between.

Not sure what to do now. I've been trying to work a space in my workshop for a minilathe but not having much success without seriously inconvenient access to some other item. If it was an easy option I would have one on order by now.

Would love to run the ML7 faster as the easy option but still cannot find bronze half bearings and shaft at a sensible price.

[SillyOldDufferModerator @sillyoldduffer]

Stephen,

There isn't a simple answer – it boils down to how much risk you're prepared to take.

a) Can you run an ML7 faster than its design speed? Yes, but there's a risk to the bearings and perhaps to other components if you crash the lathe at high speed. The faster you go and the longer you do it for the bigger the risk.

b) Can you run an ML7 for hours on end at 2000rpm? Yes but only if the guy who told that's OK also promised to replace the bearings if he's wrong.

Things you don't know:

• The current state of your bearings. Are they 'as new' or nearly worn out? If worn out then they won't last long at high speeds
• How effective is the flow of oil through your bearings? If the flow is impeded, or you're using the wrong type of oil, expect trouble.

There are a couple of things you could do to reduce the risk:

• Force feed the oil with a pump rather than Myford's gravity feed
• Monitor the temperature of the bearing and shut-down as soon as it gets hot. ( 'Full Speed and damn the consequences' in a WW2 battleship apparently involved teams of sailors cooling bearings with fire hoses.) The reason is when oil gets too hot the lubricating film collapses and the resulting metal to metal contact damages the bearing.

One thing you do know – the high cost of replacement bearings. That's the minimum pain you suffer if over speeding goes pear-shaped. If you're comfortable with that level of pain go for it. I wouldn't overrun an older lathe for long periods, but it's not daft to do it in short bursts on special occasions.

The reason I suggested a mini-lathe in an earlier post is because they're fitted with ball-bearings. Much more predictable.

Dave

 

 

Edited By SillyOldDuffer on 12/11/2017 20:30:37

[Stephen FollowsParticipant @stephenfollows82099]

I have thought of fitting ball bearings to the Myford, (two each end), at least the shaft wouldn't get hot. Not sure if they would fit in the existing clamps.

[Andrew Moyes 1Participant @andrewmoyes1]

Dave – I was simply passing on my first-hand experience. The top speed was doubled to 1300 not 2000 rpm. The lubrication was just a couple of drops of oil every hour with the standard drip oilers.

I’m interested; have you had ML7 bearings that have overheated?

Andrew

[Stephen FollowsParticipant @stephenfollows82099]

My reference to 2000rpm was not from a post on here.

[duncan webster 1Participant @duncanwebster1]

Someone described converting an ML7 to roller bearings in either ME or MEW not too long ago. Looked way too ambitious for me, but it worked for him.

Perhaps that's an opening for an entrepreneurial type, new roller bearing headstock for your myford.

[Brian WoodParticipant @brianwood45127]

Duncan,

The article was in MEW about 18 months ago. As for setting up to remodel the ML7 headstocks for customers, it would be unrealistic in that far more time would be needed than can be realistically charged for, quite besides needing suitable machinery being available to do the work.

A one off by the individual was how I read the article. It did in my view also rather weaken the bearing housings by boring them out to contain roller bearing units instead, there was little meat left to contain them at the end.

Regards Brian

[martin ranson 2Participant @martinranson2]

Stephen … I bought a Newton Tesla VFD about 13 years ago, the small size they call CL 400 … it is rated at 400 watts putput … definitely the best thing I ever bought … it has been well and truly hammered over that time … on some days it has been run for about 10 hours and has never yet got anywhere near hot … just hand warm … it has never hiccupped at all … my only minor comment is that the emergency stop button is a bit near the ordinary stop button.

Its speed range is quoted as between 200 and 1800 RPM … I made a new drive pulley from ali. bar with a diameter of 1. 75 inches … so, along with the large pulley on the headstock my spindle top speed is about 630 RPM … a larger pulley on the motor spindle would give corresponingly faster speeds on the lathe spindle.

I ended up fitting the motor round by 180 degrees so it ran in reverse relative to the desired rotation … this was simplicity itself to reverse 2 of the 3 motor wires … I did check with Newton Tesla first.

hope this is some use … martin

[Author]

Posts