Craftsman Lathe 351.217150 Not Running Properly

Dean Suminski

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Hopefully I didn't miss a post about this when doing a search. I got this lathe for free so decided to see if it would work. The Reeves drive pulleys and shaft needed to be polished so they would move back and forth freely. I lubricated all the bearings. I made sure all the shafts turned freely with no slop and they did. I ran the motor with no load on it and it seemed to run well. So I put it back together and turned it on. It started turning with a sort of loud whine. And as I turned the speed up it slowed the motor down and when I got to 2000 it was really slow. When I backed off the speed control to r.p.m. s picked up and the whine almost went away. I put a round dowel on the lathe and with a scraper tool I was almost able to stop the machine. The Reeve speed control seems to be working well. The motor drive belt isn't slipping. Is the motor shot? Is there something else wrong? Is the thing worth saving? Do you need more info? I have read enough to know Sears doesn't support this machine any more. Thanks for reading!
 

Roger Tulk

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Because of what you are describing, I would think the problem is in the spindle shaft, and not in the motor or Reeves drive. I wonder if it would be worth replacing the bearings in the spindle shaft. If you haven't alreaady done so, it may be worth knocking out the spindle shaft and inspecting the bearings for wear.
 

Vaughn McMillan

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I think several of us have owned that lathe in the past. Although Roger's suggestion to look into the bearings is a good idea with just about any used lathe, I never had any issues with the bearings on mine, and I'm not sure how bad bearing would cause the speed to slow down as you increase the speed on the Reeves drive. The problems I had with mine were belt or wheel related. The recurring problem I had was with the the Reeves pulleys getting sticky and not moving on the shaft as they should. (It sounds like you've already handled that one, at least for now.) But I also had problems similar to what you've described when the Reeves belt got too worn, especially being able to stop the spindle with light cuts. Another issue I had was with the little toothed drive wheel that goes on the motor shaft. I ended up having to replace that wheel at one point because the teeth were wearing down and/or breaking off. Here's a shot of the new and old ones, old is on the right.

Drive Wheel 1 800.jpg

Although I turned some nice stuff on my Craftsman lathe, in the end I got tired of spending more time working on it than turning on it, so I sold it on Craigslist for about what I paid, and moved up to a better lathe.
 

Dean Suminski

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Thanks for the replies!

I do have a Rockwell-Delta lathe from 1956 which works just fine. I will check out the bearings on the spindle shaft. But when I had the lathe apart the bearings seemed very smooth. I will also look at the toothed drive on the motor shaft a little closer. Thanks for the pics! If that doesn't seem like it will be fixable I think I will just scrap it.
 

Charles Lent

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Please don't scrap it. There are those of us (me) who would be willing to re-build every piece of that lathe from the pan up. If within a couple of days drive from Central NC, I would be willing to quickly and efficiently get it out of your way for you.

It sounds to me like maybe there is something wrong with your motor. Can you tell me more about the motor, what voltage you are running it on, etc. ? Is it 3 phase or single phase ? Are you sure ? I'm asking this because electric motors that are not hooked up correctly, or have problems in their windings can, and do whine quite loudly. If they are not shut off quickly when they sound like this they usually let the magic smoke out.

Charley
 

Ryan Mooney

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Also worth trying to figure out where the noise is coming from - you can use a screwdriver as a makeshift stethoscope by putting the point on various parts and holding your ear up to the handle; it does an amazing job of amplifying the sound.

If its just the motor you can usually replace those for fairly low money as well.. but definitely worth trying to figure out what it wrong before getting to carried away.
 

Vaughn McMillan

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...It sounds to me like maybe there is something wrong with your motor. Can you tell me more about the motor, what voltage you are running it on, etc. ? Is it 3 phase or single phase ? Are you sure ? I'm asking this because electric motors that are not hooked up correctly, or have problems in their windings can, and do whine quite loudly. If they are not shut off quickly when they sound like this they usually let the magic smoke out.

Charley

The motor in that model of Sears lathe is an oddball one, not a common NEMA form factor as far as I know. It's 120v single phase. You're right, the problem is quite possibly in the motor, but the replacement won't be as straightforward as it would be on most other lathes.
 

Dean Suminski

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Okay, I won't give up on it yet. I live in Portland, Oregon. As far as I know it is a single phase motor although I don't know how to check that. I checked the wiring diagram shown in the manual and it can be wired for 220 or 110. It is wired for 110 according to the diagram provided in the manual. When I turn the speed up it does speed up some but then does slow down like it is laboring. If I back the speed down from say 2000 setting to 1600 it does speed up. However I am sure it is slower than the speed it is set at. And as stated previously I can almost stop it from turning using a scraper tool.
 

Vaughn McMillan

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... If I back the speed down from say 2000 setting to 1600 it does speed up. However I am sure it is slower than the speed it is set at. And as stated previously I can almost stop it from turning using a scraper tool.

This makes me strongly suspect the Reeves belt is shot or the Reeves pulleys are not adjusted correctly.

And yes, it's definitely a single phase motor, but that has nothing to do with the problem. ;)
 

Charles Lent

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Does the motor have a bump (wort) on the side of it? If so, it is a capacitor start motor and the capacitor or the centrifugal switch inside the non-shaft end of the motor may be the problem. Also, how easy is it to turn the lathe over without the belt connected to the motor? Maybe the friction load is too great for the motor to spin - possible bad bearing or something rubbing.

You are too far from me to come to get it (opposite coast), so I'll continue to try to help you find the problem and fix it :), but please don't junk it..

Charley
 

Vaughn McMillan

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Does the motor have a bump (wort) on the side of it? If so, it is a capacitor start motor and the capacitor or the centrifugal switch inside the non-shaft end of the motor may be the problem. Also, how easy is it to turn the lathe over without the belt connected to the motor? Maybe the friction load is too great for the motor to spin - possible bad bearing or something rubbing.

You are too far from me to come to get it (opposite coast), so I'll continue to try to help you find the problem and fix it :), but please don't junk it..

Charley

Charley, the motor on these lathes is not your typical motor. It's built into to the headstock, and not a standard NEMA configuration. You have to do a lot of disassembly just to get to the motor. As far as I recall, it has no capacitor or centrifugal switch. The stator and armature are sold separately. (Or at least they used to be...they're no longer available according to the Sears website.) Parts numbers 56 and 57 in this diagram shows the motor:

http://c.searspartsdirect.com/lis_png/PLDM/50021033-00001.png
 

Charles Lent

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Ah, the original photo looked like the lathes in my high school shop, which had single phase AC motors behind them and a flat belt and step pulleys for changing speed. That parts diagram looks like it is a DC motor with brushes. With a DC motor there is an electronics package somewhere that produces a DC field voltage as well as maybe an adjustable, and likely also reversible, DC voltage to feed the motor armature through the brushes. For this type of motor the field voltage may not be at the level required for the motor, due to aging or defective components in the power supply, which would explain the noise. The same could also hold true for the armature power supply. Quite likely the filter capacitors have gone bad from age in these power supplies, allowing AC (or pulsating DC) to reach the motor. This would definitely cause the motor to have an unusual and loud whine and speed loss/available torque.

Can you post a clear picture of the motor name plate? Can you find and post a clear picture of the inside of the motor control box or PC board? Is there an electrical schematic or wiring diagram available? Please post a copy of it too, if you can find it. I may be able to help further if you can post any of these.
I'm a retired automation engineer (EE) with considerable experience on DC and AC motor control systems.

Charley
 
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Vaughn McMillan

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Charley, I no longer have mine, but there are no electronics in the box. It's 120v single phase. My current lathe is a Powermatic 3520B, so I'm familiar with DC motors and phase converters.

Here's the owner's manual. The parts diagrams and such start on about page 25:

http://www.manualslib.com/manual/495625/Craftsman-351-217150.html?page=1#manual

You can see it's not in the same league as the old lathes we had in high school shop class. (Lots of plastic and non-standard parts.) It's not a bad lathe - as I said earlier I turned some nice stuff on mine. When they work, they work pretty well, but they tend to break down more often than most other lathes. The bed, tailstock, and spindle are pretty decent, but the drive mechanism and motor are the odd ducks in the pond. Unfortunately, it'd be next to impossible to convert it to run with an external motor.


Craftsman%20Lathe%20Catalog%20Shot.jpg
 

Dean Suminski

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I am overwhelmed at your interest in this lathe and really appreciate it! I will be happy to take pictures and post them but you have to tell me how to do that. Can I put them on Picasa 3 and then get them on this site? The lathe is covered right now because it is raining here. Suppose to be nice the rest of the week.
 

Ryan Mooney

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That is a strange looking duck alright. I'm a smidge surprised at how they managed to fit all that into the headstock; impressive in a way. The rest of the unit seems study enough.

It seems like you could possibly cut the back of the headstock open and convert it to use an undermount motor with a jackshaft off of the back if the motor is truly shot. Whether or not its worth the effort is a bit of a judgement call as that's a somewhat major project... and certainly not at the expense of trying to fix it without doing that :)

Vaughns theory that something isn't quite up to snuff with the reeves seems pretty likely, when those work they're pretty decent when they don't they're a real pain.
 

Ryan Mooney

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I am overwhelmed at your interest in this lathe and really appreciate it! I will be happy to take pictures and post them but you have to tell me how to do that. Can I put them on Picasa 3 and then get them on this site? The lathe is covered right now because it is raining here. Suppose to be nice the rest of the week.

If you have the pictures on your computer you can just upload them here. Click the icon with the frame and tree - this one:
screenshot.jpg

Then just click on the "from computer" tab, then "browse", select the file(s) you want to upload and then click on the "Upload File(s)" button.

You can also use the same process if you have a URL to the actual image file that the site can access (sometimes that's complicated due to permissions, etc..).
 

Vaughn McMillan

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...It seems like you could possibly cut the back of the headstock open and convert it to use an undermount motor with a jackshaft off of the back if the motor is truly shot. Whether or not its worth the effort is a bit of a judgement call as that's a somewhat major project... and certainly not at the expense of trying to fix it without doing that :)...

Trust me, it's not worth the effort, and I doubt it's possible at all. The motor, the drive shaft, and the spindle are deep within the headstock, with other things between them and the headstock case. I think this thing was designed by automotive engineers who are used to cramming 10 pounds of stuff into a 5 pound box.
 

Dean Suminski

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Here are some pictures. Thanks for telling me how to do it. There is no plate on the motor that I could find. The big belt is toothed. I can remove the bottom half of the Reeves drive outer half no problem. Also the inner half if I would remove the spring retainer on the upper half. I can slide off the upper part of the Reeves drive no problem also. When the machine is assembled both the bottom and the upper parts of the Reeves drive move. I couldn't get a clear picture of the smaller belt but it doesn't seem to slip when the machine is running. All the bearings turn smoothly. When I turn up the speed it doesn't seem to match what it is set at and slows down with a howling sound. If I back it off from a higher speed it actually speeds up and the howling is diminished. Nothing appears to be rubbing but something is amiss.
 

Vaughn McMillan

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I stand corrected...it looks like there is indeed a centrifugal switch on the motor. Still, if the motor is running at a steady speed, I'm pretty sure the switch is OK.

Are you seeing any slippage of the Reeves belt? Also, disregarding the speeds printed on the face of the headstock, do the sheaves of the lower Reeves pulley open and close as expected from one extreme end of the speed knob to the other? As I recall, there's a gear and yoke thing attached to the speed knob that moves the Reeves sheave back and forth. If that skips a tooth or two, it can limit the amount of movement you can get with the speed knob.
 
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