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Warco BH600G - Motor hums but won't start

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Michael Smith 2623/03/2022 20:52:27
34 forum posts
6 photos

Hi all,

Me again - I ordered some Warco headstock oil and slideway oil which arrived today. I oiled everything up then had to do a bit of troubleshooting to get the lathe up and running since a safety switch wasn't triggering so had no power to the motor. Once I'd sorted that out I started having a bit of a play with the lathe - turned some brass down and was generally having a good time.

Stopped the lathe and decided to try turning down a bit of mild steel - swapped that out in the chuck then went to start the lathe and the motor began humming but wouldn't spin.

Just wondering if anyone has any advice on what the issue might be - I'm thinking blown start capacitor but could it be anything else and where am I best to start troubleshooting the issue?

Any advice gratefully received!



Hopper23/03/2022 21:25:34
6690 forum posts
347 photos

If you can turn the chuck by hand to check nothing is jammed then yes possibly it's the start capacitor or the centrifugal switch if it has one. Or associated wiring disturbed during moving.

Michael Smith 2623/03/2022 21:53:52
34 forum posts
6 photos

Thanks Hopper!

Chuck turns by hand and the humming sound is definitely coming from the motor. I'm not looking forward to taking it off to check!

AJAX23/03/2022 22:08:11
395 forum posts
42 photos

If the motor hums but does not turn at normal speed then you should disconnect the power before you burn the motor windings out.

If it is a single-phase capacitor-start motor then it should be possible to run the motor by turning the spindle (ideally close to full/synchronous speed) and then applying power. Depending on access, it may be possible to do this with the motor still connected to the machine. It would be advisable to disengage the motor from the drive train before attempting this procedure. If you use a "pull-cord" to start the motor (as demonstrated in the linked video) it is ESSENTIAL the pull cord is fully released from the motor spindle BEFORE power is applied. Also, do not wrap any cord around your hand! If the motor then runs under power you can then look at the capacitor (likely culprit) or the centrifugal switch. The linked video also shows how function of the centrifugal switch can be checked using nothing more complex than a battery and light bulb.

Ady123/03/2022 23:55:24
5175 forum posts
738 photos

I've had a sticky centrifugal switch a couple of times

Had to start it by hand pulling the chuck and once my hand was clear... switching on

you grip one chuck jaw with a forefinger and flip the spindle

in the parlance of a 1930s lathe manual, "pull smartly towards yourself before switching on!"

I think it was a bit of dirt or oil, in one case it happened after oiling the motor bearings

It tends to blow my 5A fuse when it happens, so don't leave it switched on when it hums because the system is definitely stressed

Edited By Ady1 on 24/03/2022 00:12:37

AJAX24/03/2022 06:25:59
395 forum posts
42 photos
Posted by Ady1 on 23/03/2022 23:55:24:

I've had a sticky centrifugal switch a couple of times

Had to start it by hand pulling the chuck and once my hand was clear... switching on

you grip one chuck jaw with a forefinger and flip the spindle

in the parlance of a 1930s lathe manual, "pull smartly towards yourself before switching on!"

I think it was a bit of dirt or oil, in one case it happened after oiling the motor bearings

It tends to blow my 5A fuse when it happens, so don't leave it switched on when it hums because the system is definitely stressed

Edited By Ady1 on 24/03/2022 00:12:37

Good advice.

John Haine24/03/2022 09:09:06
4718 forum posts
273 photos

If the capacitor is accessible, and the connections, it might be worth just replacing it, motor caps are cheap. Look at the data on the side of the existing one to get the right value and working voltage. Many suppliers have been mentioned here, for these even RS are reasonably priced. If that doesn't solve the problem then it's probably the centrifugal switch, but getting at that is harder. Ideally if you have to take the motor off you might consider replacing it with a 3-phase + VFD...

John Doe 224/03/2022 14:16:26
99 forum posts
15 photos

Could some oil from your oiling have got into the centrifugal switch in the motor? Seems a big coincidence that this happened soon after you did that.

mgnbuk24/03/2022 15:48:44
1207 forum posts
72 photos

Do Chinese single phase motors have a centrifugal switch ? The capacitor may be permanently connected (PSC).

Does the machine have forward / reverse capability - if so, maybe look at the reversing switch / contactor arrangement.

Nigel B.

old mart24/03/2022 16:17:20
3908 forum posts
268 photos

Trying to remember the details of the drill mill motor which is 1 1/2hp single phase with a capacitor, it definitely has a centrifugal switch. And there is also an overheat cutout which had to be changed, which might be in the terminal box. The mill is Taiwanese. With the motor off, it will be easy to find out whether the switch is present.

Edited By old mart on 24/03/2022 16:19:44

AdrianR24/03/2022 16:18:51
597 forum posts
36 photos

I had exactly the same issue with my BH600G before I bought it. The short answer was a loose connection in the control box. After tightening all the screws on the contactors the motor started up normally.

First are you sure it is the motor, when applying power to the lathe, if all the safety switches are closed you get a clunk as the main contactor closes. No clunk then a safety switch is open. There is a small hum from the 24V transformer all the time.

If I remember right (ref pg 65 of Grizzly manual) the problem was the overload contactor FR had worked its way loose from KM1 (top left)

FR hangs under KM1 and is held in place by being screwed into T1, T2 and T3 on KM1.

In normal operation K3 (top right) closes, then for Fwd/Rev KM1 OR KM2 close. For testing, it is possible to push the centre of KM1 OR KM2 and start the motor.

The motor has connections U1, U2, V1 and V2. In the control box U1 = Neutral and on KM1 T1 = U2, T2 = V1 and T3 = V2

When running Fwd

U2 = Live

V1 = Neutral

V2 = Live

When running Rev, V1 and V2 are reversed.

U2 = Live

V1 = Live

V2 = Neutral

BTW It does not like starting from cold at a high spindle speed, releasing the belt tensioner lets the motor spin up to speed first.

Hope it helps


Howard Lewis26/03/2022 16:51:55
6311 forum posts
15 photos

Twice, I made a fool of myself, and wasted an afternoon, each time, trying to find why the motor would not run.

Then I spotted that the Stop button had been pressed, and latched in.

Unlatch it and a useable machine again!


john fletcher 127/03/2022 12:14:39
805 forum posts

As you say the motor hums, so its not the machine wiring, its the motor. As others have said try the string idea but be very very careful. By using the string idea you are eliminating the motor start winding, the capacitor and centrifugal switch and if the motor runs then one of those three are faulty. I haven't seen one your type lathes, but the motor is available then a capacitor change might be the easiest to do. For test purposes ONLY and with slack vee belt, two old 5 foot fluorescent light capacitor connected in parallel will be OK in place of the original one, after all that its a strip down. If you send me a PM with an email address I 'll send you more details. John

MikeK28/03/2022 02:01:57
226 forum posts
17 photos

Above posted video is a good source for diagnosing the problem. Straightforward and clear. Should be able to find the issue with just that.

Steve Neighbour28/03/2022 10:32:08
120 forum posts
1 photos

Couple of thoughts ?

Humming could simple be a cooling fan (or invertor if fitted)

Checked all fail safe interlocks or emergency stop button(s) they can be problematic sometimes

Windy28/03/2022 11:38:57
892 forum posts
190 photos

My capacitor went when doing metric screw cutting on off was the culprit since fitting that basic belt clutch and on off on with no load things ok on my early WARCO 600.

colin hawes28/03/2022 18:16:28
559 forum posts
18 photos

My cheap bench drill failed to start in the same way and it was due to the under rated capacitor failing; it had a 250v capacitor but for reliability it needs to have a 380v rating .the replacement capacitor is a little bigger and required a larger housing as it is in an exposed position. The original just lasted the guarantee but the replacement has worked for many years. Colin

noel shelley28/03/2022 20:25:27
1444 forum posts
23 photos

Colin raises a good point about voltage, go for a 400V cap. Where are you ? there are several who may be able to help you ! Noel.

AJAX28/03/2022 20:49:18
395 forum posts
42 photos

A capacitor may fail for reasons other than voltage rating. I had a 240V induction motor that was fitted with a starting capacitor that had a much lower working voltage rating, about 120VAC if I recall correctly. This seemed low, but on investigation I found voltage across the capacitor was always considerably lower than the supply voltage, presumably due to inductive reactance of the winding.

Michael Smith 2628/03/2022 21:36:40
34 forum posts
6 photos

Hey everyone - sorry work is crazy and wife is travelling so solo parenting and it turns out toddlers don't pay much attention to DST clock changes at bed time.

I got the motor off last night - definite hum coming from it and no motion so figured it was a cap. Fortunately had managed to order all the bits so after taking it off and checking the caps with a multimeter the run cap was barely registering any capacitance. It had taken a bit of time to get up to full speed when it started so figure they were just old and spent.

Wired the new caps in - clamped the motor to a small table next to the lathe and rewired in the power and it started first time on a test run without the hum. Unfortunately the run capacitor I'd sourced was the correct voltage and microfarad rating but much larger than the original - quick search tells me I'm going to struggle to find a replacement in the correct dimensions (it's a CD60 but all the ones I found online were much bigger) so going to need to bend and weld some sheet metal to create a new cover or experiment with 3D printing in ABS.

Decided that whilst I have the motor off I might as well bite the bullet - so called Newton Tesla today and put in an order for a 2hp 3 phase motor, VFD, potentiometer and small screen I can mount to the VFD enclosure to show hz/rpm. Living on the coast I don't really want the VFD out in the open.

Going to wire those back into the lathe control box and turn the single phase motor into a belt grinder since they cost as much as a small lathe and it'll be good to build the bits myself using the new (to me) lathe.

Edited By Michael Smith 26 on 28/03/2022 21:37:40

Edited By Michael Smith 26 on 28/03/2022 21:38:25

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