Sewing machine motor

There have been several references of late to using industrial sewing machine motors to drive lathes. Friend of mine has acquired a very small horizontal mill, no motor. I've been on ebay and am bewildered. Does anyone have a link

Hi Duncan

Sorry no ebay link. I have purchased a couple from Aliexpress in the past. They all seem to be the same, apart from the motors which have differing power ratings. I don't think this is a marketing ploy as some sellers offer a range of power outputs. There is also the issue of the necessary foot control modification which has been addressed in a couple of posts and elsewhere on the internet.

A possible alternative ( not seen any reviews on this one ) is a similar motor and controller but without the hardware and foot controller part, i.e. a more universally applicable setup. There were some comments made about this toward the end of a recent post on electric motors. This was primarily in respect of electrical safety and compliance with ( UK ) regulations ( not all of which I agreed with ) but nothing about how well the units function.

Hopefully someone will be along shortly to provide more specific advice.

Pero

The motor selection will depend on the power rating that the mill requires. Find the motor size that was originally fitted. Does the mill have gear or belt speed adjustment. If variable speed is needed, remember that the motor torque is reduced at slow motor speed.

Some smaller sewing machines have variable speed via a foot pedal while other large commercial machines run at constant speed and use a mechanical clutch for stopping and starting.

I fitted a 750w sewing machine servo motor to an Alexander engraver to use it as a milling machine. I purchased it from a UK supplier - https://www.college-sewing.co.uk/accessories/motors-accessories/servo-motors. It works very well but I am only using small cutters usually on aluminium.

I have only been a passive observer so far, Duncan … but I think this is representative of what is being used:

**LINK**

https://www.ebay.co.uk/itm/126001208667

MichaelG.

I'm pretty sure that an older posting on this forum led to me having this link (for this particular item) tucked away;

Industrial-sewing.co.uk - Jack 750w Heavy Duty Servo Motor

..however it hasn't been tried or tested by me, so make of it what you will - to me it looks like a reasonably competent set-up ?

Edited By DiogenesII on 28/08/2023 08:26:11

Whatever motor is finally selected, a horizontal mill, even a vey small one, needs low spindle speed and fairly high torque to do itself justice. Since sewing machine motors seem to have quite high rated speeds, I wonder if they're the ideal type?

Speed reduction, from the motor to driven shaft, will be a torque multiplier. Power is power at whatever speed is chosen/available. Torque is basically “shaft speed x power”. Expect up to 10% losses in each stage of speed reduction (nothing is 100% efficient).

I got a vevor brushless 750w one and first impressions are very good

Push of a button gives you reverse

I tested it on my Drummond M through the countershaft for half a day which takes a bit of grunt

There's one being used at the end of this thread

Edited By Ady1 on 28/08/2023 10:19:31

I have a Jack industrial sewing machine motor fitted to my Pultra which I'm very pleased with. I've checked the internal build quality and also went as far as reverse engineering the circuit to check the design. There are others at lower cost, which I haven't bought as these come directly from China. Whereas when I bought my Jack and Tysew units they came from London and were here the next day.

I also tried a Tysew type which also performed well but the speed setting input was more difficult to convert to a potentiometer driven than the Jack.

I have noticed a worrying trend on eBay that items appear to be sold from a UK address but at the bottom it shows the address as being from China. I prefer UK stocked items, although they may be more expensive, as I know I won't get stung for possible import duty/VAT and collection fees etc

CS

My point was that a fairly high speed motor may not be the most suitable type for a small horizontal mill, which needs much lower speeds than a typical lathe. The speeds I use on my small "Zyto" are generally between 100 -200 rpm. This is from a 1400 rpm motor, so needing a 14:1 reduction ratio, with no built in back-gear. Mechanical speed reduction is quite cumbersome and electrical control can result in quite high torque loss, a fair bit is needed to drive a 3" or 4" dia cutter in steel. Using a 3000 rpm motor, as linked to in this thread, is even less attractive.

I think it quite difficult to understand the drive requirements of a machine and especially an old one where design data has been lost. As I see it, ignoring the machines capability, the power and torque needed is down to the cutter type and the rate that which material needs to be removed.

Usually machine and spindle rigidity determines how much cutting force can be applied which gives the upper limit to required torque and the rate of material removal determines the cutter speed and therefore power required.

For commercial production you may wish to maximise the capability of the machine but where time is not critical you may wish to operate the machine at say only 10% of its capability.

There is probably a sweet spot for operating machines regarding spindle speed and cutting pressure and a similar one depending on the material being cut and the finish required so a lot of possible permutations.

BLDC motors provide constant torque over their full speed range which is determined by the stator current. The upper current limit and therefore the maximum torque it can provide is determined by resistive copper losses and how well the stator can be cooled and ultimately limited when magnetic saturation occurs. A motor can be subjected to short infrequent overloads determined by the thermal mass of the motor stator and the temperature tolerance of the winding insulation. Again many factors to take into account when choosing a motor which can be made more difficult if you don't know the intended loading or use factors.

A horizontal mill is likely to need low spindle speed and high torque so a 5k rpm BLDC motor will require speed reduction in order to maximise power. If the machines original motor was a common 1400 rpm type it is likely to have this already so maybe this needs to be tweaked to suit.

CS

Thanks, I'll pass the info on. Can't find original motor size as we don't have a manufacturer for the mill. It is very small. He's intending to use it fot fluting rods for gauge 0 & 1 model locos, so no great power needed. I feckon he'd be best with 3 phase and a VFD, but these sewing machine motors seemed popular so I said I'd get some info. 750 W at 3500 would still be over 300 W at 1500.the machine has a countershaft, so getting down to 250 rpm should be possible, about right for a 1" woodruff cutter.

A small horizontal mill can be a useful tool for various model loco ops. Not as vesatile as a vertical mill, mine doesn't get used every day but it's well adapted for certain types of job such as fly-cutting smokebox saddles, chimney and dome bases etc as well as using small horizontal cutters and slitting saws. I'd miss mine.

Edited By Clive Brown 1 on 28/08/2023 15:54:44

Duncan

I would quite happily use one of these sewing machine motors on one of my projects and in my own workshop but would be wary of recommending them to someone unless they fully understand the 'risks'.

As I and others have mentioned their electrical safety does not comply with UK regulations. The two main shortcomings are that all of the wiring and circuitry is directly connected to the incoming mains supply and the fact that the connectors are not mains rated.

The speed control uses a magnet and a Hall effect sensor and whilst the sensor operates on 5V the 5V supply is not isolated so indirectly has a path to mains voltage. Even if one were driving the magnet position via a mechanical linkage the sensor wiring and its enclosure etc should be rated for mains voltages.

I have not done any detailed examinations of the have (but never got round to using yet) but I would imagine that even the keypad only has an easily damaged thin membrane between the operators finger and mains voltage.

Ian P

The Jack motor and controller is not classed as a domestic product so should be installed by a competent person familiar with electrically safety issues.

In my view a safety improvement can be made by ensuring all metal parts are earthed via supplementary bonding conductors that are visible for routine checking.

The connectors are electrically rated for high voltage but have additional protective "boots" to prevent live conductive parts being touched by the standard 3 mm diameter test rod that simulates a small electrical screwdriver.

A supplementary plastic cover will provide a second level of protection.

The control/setting buttons use small micro-switches so if the plastic membrane cracks direct contact to high voltage is unlikely.

CS