Myford ML7 accuracy

[SillyOldDufferModerator @sillyoldduffer]

Fingers crossed, as one who has yet to damage his Chinese electronics:

1. Stop and start the machine with the control potentiometer set to the lowest speed. Banging in and out with the power supply set to deliver high power is asking for trouble.
2. As hobby machines aren't built for continuous heavy work, best not to take long aggressive cuts. Don't labour the machine or and check the motor isn't getting hot. There's a reason industrial machines are 10 to 20 times more expensive!
3. Let the machine cut at it's own rate. A bad tempered gorilla in a hurry is much more likely to damage brushes, strip gears, smoke motors, and pop electronics than a skilled machinist. A skilled machinist is also more likely to react to blunt tools, work hardening metals and other mishaps. If the machine isn't cutting cleanly, you may be doing it wrong.
4. Some early mini-lathes risk swarf getting into the control box via the lead-screw hole. Protect the gap with some sticky tape or a short guard. Later mini-lathes pass the lead-screw through a protective grommet.

Not sure what the relative failure rates are, but note this forum has many posts asking how to fix single-phase motors and duff Dewhursts! Certain older machines are also a bit too delicate for comfort, nonetheless they last for years provided they are treated with respect.

Watched a neighbour using his electric drill on Sunday: won't last, he's far too heavy handed!

Dave

[Howard LewisParticipant @howardlewis46836]

If it will cheer anyone, I know a jewelry maker who uses an OLD Myford ML4 for his work (Helped him get it up and running )

It may not command the price of a 7 Series, but does the job as far as he is concerned. He does not envisage doing any screwcutting, although having a complete set of chanewheels.

It just depends upon what level of accuracy is requited.

If a pair of ear rings differ in diameter by 0.005" it probably won't matter.

Possibly a Drumond, Myford M, ML1, 2, 3 or 4, a Loughborough Training lathe or a Boxford T might be adequate for the OP's purposes. Air tight fits, or screwcutting would probably require a more sophisticated machine,

Many a good tune played on an old fiddle!

Howard

[David George 1Participant @davidgeorge1]

Hi Cal I make some jewelry as well as models and replacement tooling like ring mandrels, stamping jigs etc. I use a M Type Myford Drummond/Myford lathe made around 1950 but it is very accurate as it has had little use by previous owners. The only problem I have is the spindle speed is only 950rpm which limits small diamiter turning like retaining pins and bushes, under 0.030 inch diamiter, for some part is difficult but do but possible with care. It has a single phase motor and has the capability to screw cut and with a vertical slide and vice it will mill as well so it is fairly versatile. Think what you may want to turn or mill etc before you buy as you may be limited by turning larger pieces on a small lathe or small pieces on a larger lathe but there are ways round both to some limits.

Rotary sculpture I made and a wire drawing jig for drawing silver wire I also made cheaper than buying one.

David

[not done it yetParticipant @notdoneityet]

Posted by SillyOldDuffer on 15/09/2021 16:09:00:

Fingers crossed, as one who has yet to damage his Chinese electronics:

1. Stop and start the machine with the control potentiometer set to the lowest speed. Banging in and out with the power supply set to deliver high power is asking for trouble.
2. As hobby machines aren't built for continuous heavy work, best not to take long aggressive cuts. Don't labour the machine or and check the motor isn't getting hot. There's a reason industrial machines are 10 to 20 times more expensive!
3. Let the machine cut at it's own rate. A bad tempered gorilla in a hurry is much more likely to damage brushes, strip gears, smoke motors, and pop electronics than a skilled machinist. A skilled machinist is also more likely to react to blunt tools, work hardening metals and other mishaps. If the machine isn't cutting cleanly, you may be doing it wrong.
4. Some early mini-lathes risk swarf getting into the control box via the lead-screw hole. Protect the gap with some sticky tape or a short guard. Later mini-lathes pass the lead-screw through a protective grommet.

Not sure what the relative failure rates are, but note this forum has many posts asking how to fix single-phase motors and duff Dewhursts! Certain older machines are also a bit too delicate for comfort, nonetheless they last for years provided they are treated with respect.

Watched a neighbour using his electric drill on Sunday: won't last, he's far too heavy handed!

Dave

I’m mildly surprised than another mod has not refuted your first claim.🙂

Even so, I agree that the first line of that point is a sensible precaution.

Personally, I think that most failures are likely caused by running at heavy load at less than sufficient speed – as Andrew points out – lousy cheap electronic design.

You touch on the problem with trying to do ‘continuous heavy work’ but carrying out heavy work at low speed seems to break the system after only a very short time (I understand ‘continuous’ as meaning without for long periods of time without stopping, not just heavily loading the machine once or twice every day for a few seconds.

Point 3 is true, but lots of users (on here) would most certainly not approve of that description as they have suffered expensive repairs with many of these machines, without behaving anything like a ‘bad tempered gorilla’. A bad tempered gorilla could most certainly manage to destroy machines serially – any machine – but these cheap offerings are far less tolerant of doing just plain fair loads at slow speeds.

I note that some Warco machines have been changed from those dodgy DC electronics – they have actually fitted a 3 phase motor with a VFD.

I wonder how many commercial machines use DC motors with dodgy electronic control. Not many, if any, I suspect….

[Ady1Participant @ady1]

A hobby lathe can get you down to tenths of a mm but for hundredths/micron work I would think that honing and lapping is the way to go

[Mick B1Participant @mickb1]

Posted by not done it yet on 16/09/2021 07:58:41:

…

I note that some Warco machines have been changed from those dodgy DC electronics – they have actually fitted a 3 phase motor with a VFD.

I wonder how many commercial machines use DC motors with dodgy electronic control. Not many, if any, I suspect….

Perhaps that's why my WM250V has given no trouble, despite occasional stalls in over-heavy cuts and screwcutting (which has saved me a few tool breakages), in several years of regular use. Other users have reported similarly. And I've never bothered to start every run with the pot set to minimum revs.

[Nigel McBurney 1Participant @nigelmcburney1]

quite an attack on the S7,particularly it drive system,my S7 about 48 yrs old,has been an excellent machine,the motor pulleys and belts are original, the top speed is good at around 2000rpm,the Eglish made motor runs well and its swich gear, an even older MK 13 amp metal clad socket totally reliable, there is nothing wrong with a good tapered bronze bearing,some of the very best plain lathes use them, never experienced any spindleproblems or vibration, any machine tool needs to be looked after,its the ham fisted with no mechanical sense who wreck any tool or machine.For jewellry or instrument turning a Boxford is ok though the top speed is bit low and considerably cheaper,though when I bought my S7 a new Boxford was far far more expensive.Another option would be an used plain lathe, if required just to turn parts for jewellery,a Smart and Brown plain lathe can be bought quite cheaply and they are superb machines if you dont know what a plain lathe is look up Lathes UK website,they are often overlooked because they cannot screwcut but who wants screwcutting when making jewellery, the long top and cross slides with large handles which spin so easily in ones hands,nearly all will be 3 phase.

[not done it yetParticipant @notdoneityet]

nearly all will be 3 phase.

That is an important, too. Single phase motors are often limited in starts per unit time. Hence, I expect, why a lot of motor capacitors fail.

Starts under load can also over-heat the start windings. Single phase machines are better if fitted with a clutch (although that is something else to werar/fail).

My LJ lathe manual advised to always reduce the (mechanical) variable speed to minimum each time before the lathe was stopped. Specifically to lengthen the 1/2 HP motor life. I’m not sure if the 5” manual is the same (twice the motor power). Now, with three phase and soft start, I never need to alter the speed control pot – because I rarely change the mechanical variable speed and set the soft start VFD to a higher pot setting. It’s limited to about 70Hz, I think.

[JasonBModerator @jasonb]

Posted by not done it yet on 16/09/2021 07:58:41:

Posted by SillyOldDuffer on 15/09/2021 16:09:00:

Fingers crossed, as one who has yet to damage his Chinese electronics:

1. Stop and start the machine with the control potentiometer set to the lowest speed

I’m mildly surprised than another mod has not refuted your first claim.🙂

Some of us have been out working and not had time to say we start our lathe and mills in whatever speed they happen to be in

I think any changes from DC to 3-phase were more to get better low down power that due to the electronics, down side is the high and low ranges don't overlap so well and you end up having to change belt position more often or put up with a higher low speed. Other makes have gone to Brushless and better quality boards.

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