Another chinese lathe rises through the smoke

My lathes have tried single phase ,three-phase plus a expensive VFD,cheap VFDs and now I use  Industrial sewing machine motors.There are some on Amazon 750W and ca 100£.

I have never made a proper job of encabsulating, electric microswitches everywhere etc and it looks rather Frankenstein but runs very well.Problem was/is that the cable from motor to panel is rather short and that is one thing I will have better next time.

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Edited By Niels Abildgaard on 15/11/2021 18:29:07

Edited By Niels Abildgaard on 15/11/2021 18:29:56

+1 for the industrial sewing machine motors - I recently fitted one to my benchtop mill - a huge improvement over the original, rather anaemic brush motor.

That said, the only malfunction I've had with these brush motors is failure of the speed adjusting potentiometer - a cheap and easy fix.

Your DC motor was rated at 500W input power, as in volts times amps your 350W induction is shaft power, an entirely different thing.

It's clear from all the recent threads

Some sell machines that have resettable overload electrical protection built in if you do something stupid.

Some sell machines with bullet proof electronics that strip the gears or fry the motor in if you do something stupid.

Some sell machines the blow the circuit boards in if you do something stupid.

All are still governed by duty cycle.

So if duty cycle is a problem for you buy something non-electronic and fit a continuously rated motor.

Is it true all induction motors are really rated on their output power? If so then I have learned something new.

I say this because I have come across ancient* 1/4 hp motors that subjectively appear to be able to deliver as much turning force as some modern 1/2 hp motors (although I have never been able to precisely measure this to confirm). I did query once with a motor man who reckoned that older motors tended to be quite significantly under-rated on the plate with respect to expected duty, to ensure operational reliability.

What I do know from experience is that Chinese ratings appear to be for the absolute, full blown, maximum power dissipation the item will tolerate at the point of magic smoke release. Numbers are based on marketing rather than considering any actual duty. For reasonable operating, I usually assume 50% of stated values as indicative/safe power.

*ancient defined as circa 60 to 70 years old

Rather depends on who is selling the motor/machine. Not all state input, see this

Hmm... yes accepted, there are brands and brands and Seig is probably upper quartile. Indeed, the article makes the point that some suppliers play a bit of a game with the numbers.

Most of what I end up with is very much from the other end of the quality spectrum to bottom of barrel stuff, so I have reasons to be cautious!

As Jason says 'it depends' , But if you can see the plate then the current will give the game away. Older ones are easy they say 1/2hp etc and sometimes it says rating CONT which is continuous or run all day industrial motor.

Like you I have an old un, mines Ac, brushed, 1/4hp, continuous, nearly as big as a modern 3HP with a fair bit of grunt.

The EU has upped the standards on power consumption with a significant increase in efficency they should go into 'supplied complete' machines

Edited By Dave Halford on 16/11/2021 21:02:06

I don't have a Chinese lathe, although my mill drill is Chinese. From what I have seen the actual lathes themselves are fine, good value for the price, especially if you look at what people want for Myfords. For what people want for a Myford in this country (NZ) you can get a much bigger beefier Chinese machine which I think would be better value.

However, the smaller Chinese lathes do have this weakness of not providing much in the way of gearing changes and instead providing a variable speed motor. A variable speed motor, however good, is no substitute for actually being able to change the drive ratio. When you reduce the speed you will still only at best be able to get about the same torque. What you need on a lathe is to be able to change the ratios, so when you turn that large diameter job, you can reduce the speed, increasing the torque, and still being able to take a reasonable depth of cut.

So if I found myself with a lathe with a speed controlled motor that needed replacing, I would be thinking about how I can also incorporate some different sizes of pulleys or gears into the drive train. Not an easy thing to do when your lathe is not working. I did do something like this with my Unimat three, which started out with a four ratio belt drive and a two speed universal type motor. It now has an eight ratio belt drive and a VFD controlled 1/8 horsepower three phase motor. If I was doing it again now, and didn't already have the little three phase motor, I would certainly think about one of those sewing machine motors.

John

The new motor arrived this morning (Arc Euro, prompt as usual). Resistance checks show 15 ohms all round, indicating that my diagnosis of the old motor was correct. I will go into the workshop shortly and fit the new motor and will hopefully be up and running later today.

Regarding the title of this post, it was done in jest, and was in no way intended to be disparaging about this type of machine. indeed, were it not for these mini-lathes, there is no way I could have started this hobby in the first place. My lathe was a spur of the moment purchase. I was in Machine Mart for something else, when I saw it offered at a reduced price as an ex-display model. I had been contemplating buying a small lathe for some time, as retirement was approaching and therefore jumped in and bought it. At the time I could lift it myself but after 13 years I imagine I would struggle now.

I have to admire the brave people who use ex-industrial machinery. I'm afraid there is no way I could contemplate using low loaders, Hiabs or even engine cranes to move my hobby equipment around. I have enjoyed the use of this lathe for 13 years and the cost of the new motor works out at less than £10 /year which I think is a bargain. I will report back when up and running (Hopefully, later today)

Anthony.

Edited By Anthony Knights on 17/11/2021 10:57:23

Anthony,

Thanks for another update and the resistance values new vs old, I will be checking exactly the same thing later tonight as my motor struggles to turn when run off a little 9v battery and I believe if the motor is good, it should spin smoothly and quietly even on a battery as small as this.

Could you do me a favour, and measure the current when the new motor is connected to a 12v supply, it should be circa 100-200ma if my googling is accurate - I'm not sure I would suggest doing the same with the old motor unless you can limit the current to protect your meter somehow.

The Chester DB7 I'm working on for a friend is a similar age to your clarke machine, and I think under the fancy clothes, they are very similar machines, although this one has had a pretty hard life by the looks of it!!

I have a Myford 280 and a Warco Super Mini (basically identical to your Clarke but green!). Now if you think a Myford Super7 is a sturdy lathe, or the Myford 254 is supreme, wait till you see a Myford 280!! It's a hell of a piece of kit. I love them both, they are both excellet machines, I'd buy another chinese lathe tomorrow if I needed one. The myford, I wouldn't replace, great machine, too expensive, unjustified. When I bought it, they were cheap.

Going off piste somewhat.

My first lathe was a used Myford ML7. It did a lot of what I wanted, as long as it was less than 1/2" diameter into the spindle,until I tried to mill, using a Rodney milling attachment.

With retirement looming, a Super 7 Sigma seemed to fit he bill.

Until finding that for a quarter of the price of the complete package, I could get a larger machine, WITH PCF, as well as all the other accessories; and with a VFD fitted and set up.

But an not a precision, model maker, just a general bodger.

Eighteen years on, am still happy with my purchase.

ANY lathe in working order and good condition is very useful asset, allowing a huge range of work to be undertaken.

Howard

Russ, motor start current is roughly double the run current even on DC, I don't think it will start properly off a PP3.

Final update.

New motor fitted, control box refitted and everything connected up. switch on and all working perfectly. Should be good for another 13 years, but I'm not sure I am.

Russ B. As you can see, the motor is already fitted to the lathe, but I have yet to refit the control box lid. tomorrow I will dis-connect the motor leads and apply 12volts from a lead acid battery and see what the current is.

Anthony

Dave, I have one of those old Century motors. Repulsion start, induction run. When they get going, the brushes disengage from the commutator and it runs like a regular induction motor. Quite exciting when it starts up! This will be one of my future restoration projects as it needs a really good clean from the previous owners.

About 15 years ago I was looking for a lathe. My first thought was "...Aha...a Myford". So I asked for a quote for a well specified, but not unreasonably so, machine from my local Myford agent. This is Australia, so in this case "local" is 2,200 km apart. They came back with in excess of AU$15,000 and a six month delivery time. This seemed somewhat excessive, so from the same shop I bought a Sieg Mini Lathe, similar but slightly smaller work envelope to a Myford, similar list of options for less than AU$1,500. Delivery Ex stock. It was in my shed within a couple of weeks.

I've made countless things on this lathe and it has performed well. Whenever it has needed new parts, they have been available at a sensible price. Of course there have been breakdowns, some my fault some genuine machine faults, but they are few and far between and always solvable.

cheers

Bill

Anthony, I love the new thread title

My motor (now) runs perfectly smoothly and spins up in just a fraction of a second off a little 9v battery much to my surprise, and draws 190 to 210ma when connected to a 3a 12v regulated supply. If I brake the shaft with my fingers it’ll draw around an amp as it slows to just a few revolutions per second.

Testing the resistance however, I have just 4ohms all round, and in fact, 4 ohms between any two at any angle, i don’t know if this is right, but it’s all very consistent.

I’m not sure what was going on with my motor, initially I couldn’t get any sense out of the resistance it was jumping all over, I cleaned up the contacts with a soft brass suede brush and then it all seemed to measure as above.

I’ve no professional expertise here bar 6 months studying DC and AC theory as part of mechanical engineering qualifications - i’m just handy at working stuff out, I assume the lower resistance is due to my higher output (claimed) 750w motor. The DC controller quite an output of 0-180vdc

I will research this light bulb test, I assume it’s a circa 50w 240vac light across the motor controller output.

I will research this light bulb test, I assume it’s a circa 50w 240vac light across the motor controller output.

Any incandescent light bulb will do - as long as its specification falls within the limits of the control board output.

ie more than 180V* and less than the true motor output power. A 50W 230V AC incandescent bulb will suffice.

* This is assuming you intend to turn up the speed control to full speed/power. Don’t try it with a fluorescent lamp.

Hi there Russ B. Checked current at with 12 volt supply and it is about 300 mA. This is with the motor fitted on the lathe and driving the headstock spindle in low gear. The armature resistance measurements I refer to are taken across commutator segments 180 degrees apart (ie. same as the carbon brush contact) hope this helps .

On a more general note, there seem to be loads of relatively cheap motor controllers on the internet, but very few matching motors.

Anthony

Every time I hear Newton Tesla mentioned, "sounds expensive" comes to mind. I recently purchased a brand new Leroy-Somer 0.25 kW 4 pole 3 phase motor with a 3 year manufacturer's warranty. It cost me £31.20 including Vat and delivery. I'm using a WEG inverter, and a suitably sized unit can be purchased for less than £100. Switches and some cable will add a little extra on top.

Edited By AJAX on 19/11/2021 05:48:05

.

That sounds remarkably good … May I ask from whence it came ?

I have just looked at their website and drawn a blank.

**LINK**

https://acim.nidec.com/motors/leroy-somer/where-to-buy

MichaelG.