# Lathe spindle motor problem



## jcmullis2 (Dec 31, 2020)

I have a 8.7x31 lathe with the factory 850watt brushless dc motor. It doesn’t have much torque and I want to get a different motor if it’ll fix that. The problem is I wanna keep it 110v. 
I can go larger to 1.5kw motor like it has for about $350 but I don’t know if it’s torque will be enough. 
The other thing my son suggested is a Nema 34 closed loop stepper motor with 12nm of torque. That will cost about $200. I don’t know if it’ll be enough to keep the motor spinning under the normal turning and parting operations either. 
Lastly is the closed loop servo. I don’t know if it’s even available in 110v or if it will be able to handle the normal loads. 
I can take lighter passes and adapt but I’m hoping to get a little more umph out of my lathe. If anyone has any experience with this please help me out. Thanks and Happy New Year!


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## addertooth (Dec 31, 2020)

Don't go stepper motor.  The working torque is less than you think, and they have a curve where torque goes way down as RPMs go up (generally speaking). 

I am surprised an 8.7X31 lathe only had an 850 watt motor.  That is barely more than some of the higher tier 7X16 lathes.


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## silence dogood (Dec 31, 2020)

There has to be something wrong with the motor or the control unit.  A 850 watt ,motor is about over 1 hp.  The  1.5 kw motor should be fine if you decide to go that route, but I would check out the original first.  I have a 8" lathe and it came with a 3/4 AC motor. .  I also have a mill that uses a 500watt brushless dc motor.  Both have plenty of torque.


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## benmychree (Dec 31, 2020)

But are those Chinese watts?


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## jcmullis2 (Dec 31, 2020)

Yeah they use that Chinese math on the thing. This lathe is basically a 8x16 with a extended bed. They even call it a wm210v-L extended and it has a 1.5 inch spindle bore diameter. 
The control board is probably the culprit from what I’ve heard others say. I don’t wanna buy a control board and it not improve things. There’s a 1100watt motor that’ll bolt right up so I might try it. I just wanna be able to part steel without any problems. Maybe someone will reply that’s changed out their motor for something stronger.


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## markba633csi (Dec 31, 2020)

JC:  It sounds like the controller is mis-adjusted. There is usually a torque compensation adjustment on the circuit board. It may not be labelled as such however.  Has this machine always been like this or did the problem just start recently?
You might try checking Youtube for info on how to set it properly
Also check out this repair service for motor controllers:
-M
www.olduhfguy.com (Pete)


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## jcmullis2 (Dec 31, 2020)

markba633csi said:


> JC:  It sounds like the controller is mis-adjusted. There is usually a torque compensation adjustment on the circuit board. It may not be labelled as such however.  Has this machine always been like this or did the problem just start recently?
> You might try checking Youtube for info on how to set it properly
> Also check out this repair service for motor controllers:
> -M
> www.olduhfguy.com (Pete)


It’s always been like this. I heard there’s pots to adjust the speed and torque but some of these lathes had different motors so I really don’t know if it does or not. I really don’t know anything about this stuff anyway and don’t wanna kill it. My son is coming over tomorrow and he knows enough to do it so I’m gonna have him try to dial it in if it has those adjustments. That would be too easy of a solution for my luck. Maybe my year will start off right. I’ll let you fellas know.


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## markba633csi (Jan 1, 2021)

Just have him mark the adjustments with tape or a sharpie so you can go back and then try them one at a time.  I bet you will be able to improve it
-Mark


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## jcmullis2 (Jan 1, 2021)

markba633csi said:


> Just have him mark the adjustments with tape or a sharpie so you can go back and then try them one at a time.  I bet you will be able to improve it
> -Mark


I was sweating it too much evidently. I called him up and was bugging him somewhat and he sent me some links to videos about trim pots and how they’re adjusted. He says it’s really basic dc motor stuff. I get off the phone and watch the videos and the videos broke it down in simple terms. I’m sure these adjustments will help. The motor is like the rest of the lathe. They slapped it together and didn’t spend any time tweaking or fine tuning things. I guess that’s somewhat understandable considering they bounce around the globe in a crate. However It would have been nice if they had included a decent manual. One that covered all the adjustments so the lathe could perform at its best if the owner set it up properly. If I can get this issue resolved I’ll have a darn good little lathe. I’ll know more in a few hours and I’m hoping for the best. Wish me luck guys. Happy New Year to everyone


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## markba633csi (Jan 1, 2021)

It's possible the factory that puts these together doesn't even _know_ how to adjust it or even try. They probably get the circuit boards from another division and just assemble and give a quick turn-on. If that.  So yeah, quality control minimal, cost minimal, let the end user do the final tweeks
-Mark
ps can you imagine a US manufacturer doing that in the 50s, 60s or 70s?  No way, their business would suffer greatly


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## hman (Jan 1, 2021)

jcmullis2 said:


> Yeah they use that Chinese math on the thing.


I'm reminded of a phrase from a Tom Waits song ... "harder than Chinese algebra"


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## jcmullis2 (Jan 2, 2021)

Well so much for me adjusting the pots on this thing. There’s nothing to adjust on the control board. The older lathes like mine had brushed dc motors and their control board has pots to adjust. Not only does it not have pots everything on it is covered with a thick black epoxy. That’s how stuff goes sometimes. 
I have a nema 34 1700oz in 12nm closed loop stepper that’s part of the cnc stuff for my mill that’s coming. It looks like it’ll swap right out so I ordered some pullies and belt. I’ll give it a try and see how it goes. I won’t be out of anything but my time since the belt and pullies can be used on whatever motor I end up with. 
If anyone has upgraded the motor on their lathe I’d like to know how it went. I see a few people have made videos of 3 phase conversion but not much else.


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## markba633csi (Jan 3, 2021)

A stepper motor won't work in your application for two reasons: first, the torque curve is wrong and second, you need a pulse generator and driver to make it rotate, not just a source of power
sorry
-M
ps that's the first totally potted controller I've heard of- bummer.  Have you considered buying another controller from Little Machine Shop?


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## jcmullis2 (Jan 3, 2021)

I don’t think it’ll work either but my son does so we’ll give it a try. I don’t know about the torque curve of the factory motor so I can’t compare them. However I can stop the factory motor with my hand and I can’t the stepper. As you probably know threading is typically done around 50 rpm.  I’m beginning my passes around 6-700 rpm and still bogging down to zero rpm. I’m okay if I keep things to light passes, and by light I mean not much more than scratch passes. Threading shouldn’t take 50 passes and I’m not willing to do that.
It’s a closed loop stepper with driver. My son is doing something with a thing called a Arduino? I haven’t bought anything other than a couple of timing pullies so I don’t have any money in trying it. 
I don’t have any knowledge of this stuff. I’m deferring to my son who thinks it’ll work. If it does, great, and if it doesn’t that’s okay too. If it fails to perform adequately I’ll buy a 3 phase motor and the pullies will work on it too. I don’t want to run 220v to that room but I will if I need to.
A control board is about $400 at the LMS for lathes about the size of mine and there’s no guarantee of improvement. I can’t believe anyone would buy one for that price. You can get a lot more motor for that money. 
I’ll let y’all know how it goes in the next episode of as the stomach churns. If anyone has thoughts on 110v motors that might be useful please let me know.


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## addertooth (Jan 3, 2021)

Then go full monte, and do the treadmill motor mod.


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## jcmullis2 (Jan 4, 2021)

addertooth said:


> Then go full monte, and do the treadmill motor mod.


Treadmill? That sounds interesting. Tell me what you know about doing that. I know some of them have nice big motors but didn’t realize they had them in 220v


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## addertooth (Jan 4, 2021)

Many treadmills have variable speed controls, this allows them to be adjusted from a slow staggering walk, to a brisk run.  They people who do it, harvest the motor speed controller from a used treadmill, and use the treadmill motor to spin the spindle.  Using the search engine in the forum, search for the word "treadmill".


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## hman (Jan 5, 2021)

I've salvaged a couple of treadmill motors, used one on a drill press.  They're permanent magnet DC motors.  Challenges include very non-standard mountings and unusual (threaded) motor shafts.  The motors are all designed to turn a flywheel/fan/flat belt pulley.  So you'll need to do some creative machining to use one.

Treadmill controllers come in two different "flavors":  There's the classic MC-60, which uses a variable resistor to set speed.  The other type (I forget the number, something like 2100?) requires a pulse train to set the speed - so you'd need something like an Arduino to drive it.

I've only used the MC-60.  It has two quirks which you should be aware of.  First off, almost the entire circuit, including the leads to the speed control pot, floats at something like line voltage ... so be careful with your wiring.  Secondly, the circuit includes a "safety" slowdown feature.  Think of somebody on the treadmill.  They might stumble and fall if the belt stopped too suddenly.  So no matter how quickly you turn the speed to zero, the controller will slow the motor down in a controlled fashion.  Oh yes ... startup can also be a pain.  The way the circuit is designed, if the speed pot is not at zero when you apply power, you have to turn it all the way down before you can get the motor to run.  The way to get around that is to put a switch between the center lead of the pot and the wire to the control board.  Turning the switch off and back on fools the controller into "starting up" at the set speed.

Alternatively, you can get a standalone DC motor controller.  If you search ebay for "90v dc motor controller" you'll find a bunch.  Just be sure to get one with enough current capacity.

As for 220 volt ... I recall seeing a post recently from an offshore member about a 220 volt treadmill controller.  I doubt you'd easily find one of those here in the US.  And a final PS - @itsme_Bernie has recently posted about having a number of DC motors and controllers.  You might want to get in touch with him via PM, and see what advice he might have.


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## jcmullis2 (Jan 6, 2021)

hman said:


> I've salvaged a couple of treadmill motors, used one on a drill press.  They're permanent magnet DC motors.  Challenges include very non-standard mountings and unusual (threaded) motor shafts.  The motors are all designed to turn a flywheel/fan/flat belt pulley.  So you'll need to do some creative machining to use one.
> 
> Treadmill controllers come in two different "flavors":  There's the classic MC-60, which uses a variable resistor to set speed.  The other type (I forget the number, something like 2100?) requires a pulse train to set the speed - so you'd need something like an Arduino to drive it.
> 
> ...


I might just give a treadmill motor a try. I seen some huge 2kw and up brushless dc motors and controllers for less than $100. They use them on electric bikes and motorcycles. They looked the most promising of anything I’ve seen so far. A 2kw brushless dc motor and controller for a bigger lathe costs about $500. The specs looked about the same so I don’t know why one costs 5 times more than the other one. I’ll get it figured out before long. Thank you for your help


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