Lathe motor power

I'm considering buying either the Amadeal AMAT210V or Warco WM240. The former has a 450 watt motor and the latter a 1.1kw - seemingly a big difference. Am I right in thinking that the higher power motor will offer more torque at low speeds and therefore allow deeper cuts to be taken (all other things being equal)? Are there any other advantages to a higher wattage motor?

As an aside, can anyone tell me if there is likely to be much difference in the noise generated by these two machines (domestic environment, SWMBO etc)

Many thanks

Paul

Lathes with speed controlled by reducing motor speed have a lot less torque at low speed than ones with mechanical speed reduction so a more powerful motor is going to be better for low speed use.

The noise will depend on what you are doing. Turn a bit of square steel bar down to round and you will make a lot of noise because of the intermittent cut. Turn a round bar of aluminium and I would expect very little noise. Milling is generally more noisy than turning so if you decide to use the lathe for milling then there will be some noise probably between the two examples above.

Martin

Thanks Martin, I should have said I've previously owned a mini-lathe and a micro-mill, I just wondered if the noise would be any 'worse' in general. I will mostly be turning very small parts at higher speeds.

Both of those are variable speed (although the Amadeal model also involves a belt change for part of the range) so I imagine they will be equally quiet/noisy!

Lathes using DC motors with speed control sem to keep blowing controller boards. Doesn't the WM240 have a 3 phase induction motor + VFD? Generally a higher power system may be less prone to blowing power devices under the same load so I'd go for that one.

No, the smallest lathe in the WM series that has VFD + 3 phase induction motor is the WM250V but there's a significant price difference to move up to that one.

Buying a machine does not necessarily mean you have to stick with that particular motor forever, I replaced my 750W DC motor with an AC + VFD equivilent on a Warco WM16.

I would say my past experience with motors has generally favoured single phase and 3 phase /w VFD setup, never had a failure to date whereas i've had 2 DC motors go kapputt for multiple reasons handling the same circumstances and workload,

that could be because i managed to miss all the nice quality DC motors such as parvalux? who knows, but thats how it's played out for me.

I'm not critical of DC full stop, they do have some very good applications but being the main driver of a powerful machine and cutting strong materials hasn't worked out for me so far, maybe i'd have needed brushless drives or a much bigger DC current to make that a reality.  So far i'm happy with the AC ones though. 

I will find out in the future because i'm planning to resurrect my CNC sherline mill with a far better brushless DC motor and drive. So i'll get my verdict, i'm hoping for positives this time round! 

Michael W

Edited By Michael Walters on 09/11/2016 12:32:36

The two lathes are similar except that the Warco has a more powerful motor. It will have beefier electronics too.

If as you say everything else is equal, then the Warco is 'better'. I wouldn't use the extra power to take brutal cuts though. Rather I'd use the extra power to give the lathe an easy life by allowing it to cruise. Overworking the motor and electronics of a hobby lathe is asking for trouble.

Dave

It's not strictly true that variable speed lathes lose torque at low speeds, the torque is actually constant.

What they don''t benefit from is the increase in torque generated by gearing down a constant speed motor.

With a decent sized motor this isn't as much of an issue as often supposed.

Finally more modern DC speed controllers are generally more reliable and the brushless DC ones seem tobe particularly reliable.

Neil

Neil, no one has said these lathes lose torque at low speed.

Martin

Sorry Martin, I misinterpreted your post.

Neil

What Neil has said is consistent with my knowledge because torque is at it's highest at near to no speed on motors but what it doesn't benefit from is full power, and it's this that it needs to handle loads, so if increasing the power gives you more speed you need to reduce it (or increase it in few cases) to what you need with a mechanical ratio.

The newer speed controllers have a compensation factor built into them, so that if it detects a decrease in speed due to load it will increase the power, which should try and bring it back to the constant desired speed that you wanted. I think this is pretty clever stuff and i hope they develop it even further.

On my AC 1HP lathe motor i can reduce the speed to maybe 5-10hz on a high speed pulley and still do thread cutting and tapping/die-ing on jog mode. This is a huge plus because the justified worst criticism of my particular model was that the slowest speed was too high for thread cutting, now i can pretty safely do things that would've been unimaginable on a single phase motor,

It's also far safer when it comes to the chuck key because of it's "coast to start/finish" mechanism where it slowly builds up frequency, meaning IF it did occur the chuck key would simply fall out rather that fly across the room at instant power, not that i would do such a habit, nor has it ever happened but i did think about that one day and the manufacturers should too. 

Michael W

Edited By Michael Walters on 09/11/2016 19:35:48

If the torque stays the same as the rpm reduces, the hp reduces. simply torque and revs is horse power. With a belt head or geared lathe, as the speed is reduced the torque goes up.

Ian S C

The big problem with this subject is always when people get confused with the terms. As Ian notes, torque is simply a force applied to turn something - like using a spanner - and it does not need to be moving, simply pulling on an previously tightened nut will apply torque even if the nut does not turn. It only becomes power when it is moving and doing some work. So Hp is the act of turning the nut before it stops turning. As it is being tightened up you are doing "Work" pulling the spanner (applying torque). Obviously, tightening the nut slowly with a long spanner is easy and you would not need much effort (power/Hp). If you had the boss watching, you might tighten it much quicker using a short spanner (which is quicker to use as your arm does not have to move so far to turn it if you are holding the end) putting more effort in and this may result in getting a bit of a sweat on, or in engineering terms "more work/Hp. So, the same torque (the nut and bolt was the same) but the time to do it changed so the work done was in a shorter time and hence more power was required. This applies in all cases off gears, pulleys and levers etc. which is why a small motor can turn a heavy load using lots of gearing to reduce the speed. It is also why motors are rated in kW (power).

Mark

It's pretty obvious that the op should go for the higher power lathe in this case and also get the plus of the accuracy report. By the time the kit is added to the other one may well work out to be more expensive. People may think that they will never need the kit but chances are that they will at some point.

These lathes often have 2 speed ranges and some people run them in the lower speed range most of the time. They do keep playing around with the speed ranges though and it may be that the max speed in the low range isn't as convenient as it was. They do this to allow very low speed screw cutting.

The Warco also seems to weigh more. Probably due to the extra bits and pieces.

I don't think that you will find noise levels a problem. If the lathe used gears for the spindle drive you probably would unless it was all rather carefully made. My machines are in the house and it hasn't caused me a problem even after fitting an inverter to my lathe which made it noisier than it was before.

John

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