smoke coming out of 9729 lathe motor connector box

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John R
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smoke coming out of 9729 lathe motor connector box

Post by John R »

I've done quite a bit of lathe work the last week and just now I noticed smoke coming out of the connector box on the lathe motor. I took the cover off of the box and could see no evidence of fire or blackened wires or anything like that, so put the box back on the tried the motor again. Same thing; smoke coming out of the box - actually out of the black grommet and screw in cap where the power cord enters. The motor didn't stop and the lathe turns but obviously I don't want to use it like this. I did a search on this on here and nothing came up. The lathe switch works fine it turns the motor off/on both forward and reverse.

This 9729 is ?? 12-18 years old and I've used extensively during that time.

Does anyone have any ideas here?
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NP317
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Re: smoke coming out of 9729 lathe motor connector box

Post by NP317 »

I would first check for loose screw connections on the wires in the box.
If you have a hand held temperature gauge that can help you find a heat source without sacrificing finger skin.

With use and current cycling it is not unusual for screws to work loose, increasing resistance in the connection, leading to heat buildup.
If you find loose screws, remove them to fully inspect the wire connections and clean them as needed.

For future security you can add some conductive joint compound to the connections before putting them back together.
I found a tube of that goop at my local hardware store, which I used when assembling 220V ac wiring for our kitchen stove I replaced.
That was to meet electrical code requirements.
No smoke or flames yet...
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John R
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Re: smoke coming out of 9729 lathe motor connector box

Post by John R »

I looked again just now and the smoke is coming out of the electric motor case where the wires pass through into the connector box. I'm going to order a new motor from grizzly.
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liveaboard
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Re: smoke coming out of 9729 lathe motor connector box

Post by liveaboard »

I'm not familiar with that machine, but generally speaking electric motors are standard items and you can order a motor with the same power, rpm, and frame from any electrical supply for far less than a spare part from the lathe manufacturer.

I would advise a 3-phase motor and matching VFD.
I added a VFD to my ancient Czech lathe and it's a huge improvement, very worthwhile.
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Re: smoke coming out of 9729 lathe motor connector box

Post by John Hasler »

liveaboard wrote: Sun Aug 02, 2020 4:12 am I'm not familiar with that machine, but generally speaking electric motors are standard items and you can order a motor with the same power, rpm, and frame from any electrical supply for far less than a spare part from the lathe manufacturer.

I would advise a 3-phase motor and matching VFD.
I added a VFD to my ancient Czech lathe and it's a huge improvement, very worthwhile.
What he said. You can almost certainly get a better motor than what Grizzly would sell you for less money.

It might also be possible to get that motor rebuilt, though that might not be cost-effective. If it were mine I'd tear it down and see if I could fix it: motors are really simple.
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Re: smoke coming out of 9729 lathe motor connector box

Post by Torch »

Those motors are 3/4 hp AC induction TEFC motors, correct? Probably the thin varnish insulating the windings has deteriorated from heat over time and now one or more windings are shorting. The motor will not last much longer. You could get it rewound if there is a motor or armature repair shop in your area, but it might be more economical to replace.

And if you are going to replace it, this is an opportunity to upgrade it. I would not go bigger than about 1-1/2 hp, just because the machine and it's associated switches and wiring are not heavy enough for a bigger jump. Variable Frequency Drive is one option. Another is DC. One popular upgrade on these machines is to source a DC treadmill motor. You may be able to get a controller from the same scrap treadmill or you can buy a Pulse Width Modulated controller separately.

The advantage of VFD or PWM is variable speed with good low-speed torque. Add a tachometer to display the spindle speed and you can dial in the exact RPM you want on the fly.

The disadvantage is greater cost and the complexity of wiring it in.
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Re: smoke coming out of 9729 lathe motor connector box

Post by John R »

20190420_160424.jpg
Guys I've already ordered and paid for the Grizzly replacement. It's on back order and according to Grizzly the next batch will arrive on 8/25. This thing (the 3 in 1) is a tool to me and not a hobby in itself. Thus I'm into the most simple/easiest fix and not some exotic do over even it would be better/stronger after I've done it. I'm no electronics expert so would really have to study up to do the things you are suggesting and am just not into it. Oh I could do it I think but I just have no interest in doing so. I'm 75 years old, bought this thing well used 12-18 years ago, and if the replacement motor I'm buying lasts as long and this original motor that is probably well longer than I will last. I appreciate the input though.

The main thing I do with this machine is replicate oem carburetor linkage from mid-50s to mid-60s muscle cars. Not heavy duty work but one needs a lathe and mill to make it look right.
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John R
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Re: smoke coming out of 9729 lathe motor connector box

Post by John R »

Well the 8/25 shipment was not received by Grizzly and they're saying the next shipment will arrive on 10/12. I've found a C32000-1 motor at Detroit Machine Tools who are the vendor for Smithy products. They've sent me pictures and mounting measurements for that motor, which is for their Midas machine (same as Grizzle 9729), and the spacing matches. I'm having a hassle with them however trying to buy their motor. I've also investigated many other motors and all of them are half again or twice the Grizzle motor's price and would require me fabbing up something to mount them to my machine. We will see how this turns out.
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Re: smoke coming out of 9729 lathe motor connector box

Post by Steggy »

John R wrote: Thu Sep 03, 2020 12:08 pm Well the 8/25 shipment was not received by Grizzly and they're saying the next shipment will arrive on 10/12. I've found a C32000-1 motor at Detroit Machine Tools who are the vendor for Smithy products. They've sent me pictures and mounting measurements for that motor, which is for their Midas machine (same as Grizzle 9729), and the spacing matches. I'm having a hassle with them however trying to buy their motor. I've also investigated many other motors and all of them are half again or twice the Grizzle motor's price and would require me fabbing up something to mount them to my machine. We will see how this turns out.
Unfortunately, it seems most Chinese machines are powered by motors that have no analog to standard NEMA frame sizes. Mounting bolt patterns are metric, as are shaft diameters. You may end up having to do an adaptation of a NEMA-standard motor. That will entail drilling a new bolt pattern into the mounting plate and having to replace the pulley, or rework it if the new motor's shaft is bigger.

You can find motors on eBay at reasonable prices, both single- and three-phase.
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John R
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Re: smoke coming out of 9729 lathe motor connector box

Post by John R »

It took me awhile but I finally got around to installing the Grizzly replacement motor and lathe bearings. The bearing installation will be covered in that thread. As for the motor it turns out that there have been three versions of the 9729 machine and I have version one. The current version being version three. I don't know what all differences there are among the three versions but as regards the motors the version three motor, which is the only one they sell now, is larger than the version one, has a bigger diameter shaft, and a larger diameter mounting ring machined at the front mounting surface. All other specs of the motor, amps, hp, etc. are the same. Thus, if you are replacing a version one motor with the currently available version three you have to get not only the motor but a new pulley and a new motor mount. The part numbers and prices for these items are p9729111tv3 motor $190, p9729117v3 pulley $30, and p9729120v2 mount $30. Apparently the mount surface got bigger with the version two motor thus the version two mount works with the version three motor. The # of terminals inside the connector box of the version one and version three motors also differs with the version one motor having four terminals and the version three having six. I'm attaching a couple of pictures here of the two versions of motors and mounts and pulleys so people can see the difference. Oh the new motor also has the connections and the capacitors under a big U shaped cover where on the version one motor they each have their own covers. This means the version three motor has to be mounted with the connector/capacitor cover towards the rear of the machine. The next post will address the wiring.
Attachments
old and new motor mounts and pulleys.JPG
motor mounting surfaces side by side.JPG
John R
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Re: smoke coming out of 9729 lathe motor connector box

Post by John R »

old and new motor.JPG
This picture shows the old and new, larger, motor side by side, and the u shaped capacitor/terminal cover.
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Re: smoke coming out of 9729 lathe motor connector box

Post by John R »

The new, version three, motor, as mentioned above, will have six terminal connections instead of four. It will also have jumpers across four of those connections. You don't want the jumpers on there so remove them. Also, because the motor has to be mounted with the terminal/capacitor cover towards the rear of the machine, the original wiring to the motor will be too short; at least mine was. So you may have to add some wire to extend the length of wiring to the motor.
Attachments
terminal boxes side by side.JPG
six terminals with wires connected.JPG
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