13" X 40" Lathe Spindle Running Hot, Tight Bearings

What I have is a Jet BDB-1340A belt drive lathe purchased used from a high school auction. Appears to be almost new.

The spindle gets hot, 140F after 15 minutes with no load, and is difficult to turn. So I back off the spindle bearing adjustment nuts. That has no effect. So I leave the nuts loose and hammer the back end of the spindle which moves it. Still runs hot and is tight. So I knock it over some more, thinking that the school might have severely over tightened it. At this point I've moved it .125" or more. Still no improvement. The chuck end now has a lot of side to side play, and the back end has none. I take a big deep throated furniture clamp (I knew it would come in handy some day) and moved the spindle back in. I hoped this would create back bearing side play. It did not. Less play on the chuck end but still no play in the back.

The bearings sound and feel fine. I've run out of ideas. Below is a cross section of my lathe's spindle. Any suggestions are appreciated.

Typically bearings don't enjoy taking a hammer blow to them... That aside, if you have a lot of side play on the chuck side of the headstock bearing, the bearing could either be damaged or the two halves aren't mated properly. Hammering them certainly didn't help.

Looking at the diagram, I suggest removing the bearing covers and seeing if you can tell the condition the bearings are in without having to fully remove them. Check and see if they're sufficiently oiled as well. I think you're going to find that either the bearings (one or both) either didn't get proper lubrication or has come misaligned. Is there any noise coming from the bearings just while hand turning the spindle?

From the diagram, it looks like it just uses tapered roller bearings, which can become separated which would cause some side play. You'd need to inspect both the casting and the spindle bearing journal to see if it's out of position in either spot. When/If you chose to remove the bearing caps, you should be able to tell if they aren't mated properly.

All of this is assuming this is with the belt tension relieved yes?

Thanks for the response.

I wasn't clear. Before I hammered the spindle toward the chuck, it had no play period. I created the play on the chuck side. Instead of using the bearing adjustment nuts to move the chuck side in, I used the furniture clamp in an attempt to create play on the back side. It didn't.

So I'm able to loosen the fit of the chuck end bearing and unable to do so to the back end bearing.

The bearings seem fine. The belt was so grippy that it didn't slip even un-tensioned, so I cut it off to eliminate it as a source of the drag. Currently there is nothing attached to the spindle.

The bearings run in an oil bath. In the photo (old photo), you can see black plugs in the fill holes.

ptsmith said:

Thanks for the response.

I wasn't clear. Before I hammered the spindle toward the chuck, it had no play period. I created the play on the chuck side. Instead of using the bearing adjustment nuts to move the chuck side in, I used the furniture clamp in an attempt to create play on the back side. It didn't.

So I'm able to loosen the fit of the chuck end bearing and unable to do so to the back end bearing.

The bearings seem fine. The belt was so grippy that it didn't slip even un-tensioned, so I cut it off to eliminate it as a source of the drag. Currently there is nothing attached to the spindle.

The bearings run in an oil bath. In the photo (old photo), you can see black plugs in the fill holes.

Click to expand...

Is there oil inside? All I can suggest is either a damaged bearing, possibly crud in the track, or a misalignment. Possibly one might not be seated in the casting straight?

When a bearing fails and locks up the spindle can continue to rotate by sliding between the shaft and inner race ID surface. There will be significant heat generated and initially very little play.

It's the belt, in the kitchen, the butler did it.

Asking questions wont fix anything.....pull it down and find the problem......you have the plans ...nothing more needed.

140F is not too hot after running continuously for 15 minutes, it's about perfect. When mines tight enough to not chatter it definitely warms up. No-load doesn't matter, it is loaded by the bearing preload. The seals on these tend to be tight fitting and yours might be on the dry side, adding to the heat but also the drag. These also can't handle overspeeding at all with a VFD, etc. Stick to the nameplate rpm.

It's common to have to tap the spindle to the right after loosening the nuts to get the spindle to loosen, the left end bearing is often pretty tight on the spindle. But moving 0.125" and then running the lathe wasn't a good idea. The difference between completely loose and over tight is less than 0.005" end play. Hopefully all bearings were tight enough on the spindle things weren't bouncing all over the place.

On my similar lathe there are sight glasses for the HS bearings, but they are useless. They fill from 1 hole only in the middle of the glass and cannot drain back to the bearing. Thus they can show the proper level of about half full all the time, even when the bearing housing is empty. Add oil to above halfway full.

I replaced the bearings in my 13x40 GH lathe last year. I had the same problem. The inner race of the back bearing was very tight on the spindle even after I removed the adjustment nuts. I wound up having to tap it off the spindle with a wood block and a 3 pound hammer. Since I was replacing the bearings anyway I wasn’t worried about any potential damage to it. Once I got the bearings off I polished the journals with 1200-2000 grit sandpaper to make installing the new ones a bit easier.

FWIW: The bearings can sound fine and still be bad. I’d pull them both to clean and check them.

Thanks everyone. I just got time to work on it again. Too many suggestions for me to respond to them all so let me just tell you where I'm at.

I noticed last night that the spacer that butts up against the back bearing fit tight on the spindle shaft and that's why I had to hammer the spindle over. I also noticed that when I pushed the spindle back with my furniture clamp that the spacer didn't move in relation to the bearing, which was puzzling.

So tonight I pulled the rear bearing cover off. Turns out that the spacer is different than the one in the drawing. It has a flange on it that butts up against the bearing cover, which prevents it from moving away from the bearing.

The spacer also fits very tight on the spindle as I suspected. I pried it most of the way off but I'm going have to get a puller to finish removing it.

That it fits so tight it will make adjusting preload difficult. If I tighten it too far I'll have to back everything off and hammer the spindle to get some slack. Then try again.

It seems I need to hone the inside of the spacer a little so it doesn't bind. But that will probably create an oil leak between the spacer bore and the spindle.

So what to do? What do ya'll think?

PS: The rear bearing looks fine, although I drained the oil and it's pretty dirty. Also, once I loosened the spacer I had the bearings loose enough that they couldn't possibly be the source of spindle drag, but it still drags. Less but it still seems like a lot. It has to be the oil seals as was suggested.

That spacer is a bearing race being used to substitute the original spacer. You may find that burrs on the spindle is the reason its tight.
Be careful to not damage those threads .

From your diagram post #1 it appears that the original spacer has a groove cut in the inside diameter for an O ring to seal the I.D. of oil. Then you have a flange with a seal for the outside diameter.
If the correct spacer cant be bought new you could make a new spacer on your lathe. It really needs that O ring seal on the inside diameter of the spacer too be able to slide on the spindle shaft for end play adjustment and still seal in the oil. Was there an outside seal running on the current spacer?
Consider new bearings while your working it. Money spent now, or more spent later with gear and or spindle damage.
.Warm that spacer up a little with a propane torch to help slide it off.

The diagram I posted was titled "13" X 40" Chinese Lathe". I thought it was an exact match. And for the most part I think it is. But the spacer is different. The pic below is a screen grab from my manual. Part #30 is the spacer. You can see the flange. You can also see the o-ring that you mention, which I had missed. Turns out the o-ring was the main cause of the spacer binding. I could not get it off, so I knocked back on. In doing so the o-ring popped out. I could now get the spacer off, although it was still a bit tight. I sanded lightly on the spindle (as was suggested) and now it fits great. I applied some grease to the spindle thinking it might act as seal. So far it has, but we'll see.

If the spindle bearings ever were good, I think they're for certain shot now. I had oil showing a little less than half way in the oil sight glass. When I turned on the lathe, the oil level would drop almost to empty. This was because the bearing rotation was pulling the oil away from the window. So I added more oil. Oddly the oil level in the sight glass barely rose, even though I filled it until was overflowing. NOW when I turn it on, the oil level doesn't change at all. I pulled the fill caps off but it didn't make difference. So I run it anyway thinking hey, it's full of oil, there's nothing to worry about. Wrong! the spindle got too hot to touch and eventually starts making some noise that doesn't sound good. So I drain the oil. I feel the oil and it's barely warm. I interpret that as the oil was not getting inside the bearings and they were running dry.

From where you are now the right way to eliminate any doubt pull the spindle and make it right.
That spindle needs to come out to assure its all good. If that O ring fits in what appears to be a groove on the end of the spacer find a replacement. Grease may hold back oil for a short time but will leak. O rings come in many sizes. match what you need if parts are obsolete.

John K's post says it well. Pull it down and find the problem. Its up to you now.
Let us know how it works out .

I tried to pull the rear bearing inner race so I could look at the rear bearing. It's tight as well. I moved it a little and couldn't move it any further. I imagine the inner pulleys and gears are going to be stubborn as well. So yanking the spindle out is probably going to be a job. At least if I'm doing it it will.

I've had this lathe for a long time. Like I mentioned it's in almost new condition, but was missing a lot of parts, including the electrical box. I decided it was easier and probably cheaper to replace the single phase motor with a 3 phase motor and VFD. I just powered it up for the first time a week ago. I've yet to take a cut with it.

I've given it some thought, and came to the conclusion that running like it is isn't going to make matters any worse. So I'm just going to run it until the bearings give out. At that point I'll replace them. In the mean time I can at least use the damn thing.

About the 0-ring. I think it's the original ring. And there's nothing wrong with it. I don't understand why it binds the spacer up. Maybe the groove has a taper to it.

If the grease gives out, I'll get some gasoline resistant grease. That should hold up I would think.

I just checked and no leaks so far. Even if it does leak, it will be very slow. I've got a sight glass, I'll just add oil as needed.

ptsmith said:

About the 0-ring. I think it's the original ring. And there's nothing wrong with it. I don't understand why it binds the spacer up. Maybe the groove has a taper to it.

If the grease gives out, I'll get some gasoline resistant grease. That should hold up I would think.

I just checked and no leaks so far. Even if it does leak, it will be very slow. I've got a sight glass, I'll just add oil as needed.

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Sometimes when bearings lock up, they spin on the shaft. Then your repair bill goes way up past the cost of bearings. Running until it fails is a bad idea.

Bill

It's not making any noise now. I had just installed a new 5/8" link belt to the spindle, so maybe that was the source of the noise.

I filled the oil back up but not as high. The oil level lowers to almost empty when the lathe is on. I'm pretty sure that indicates that the bearings are spinning. So at least for now I think I'm OK.

JCByrd24 said:

140F is not too hot after running continuously for 15 minutes, it's about perfect.

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I've read the same thing elsewhere, but it doesn't seem that's the general consensus. I'm going to take your word for it though and not worry about it.

To follow this up:

I live in Texas and it's currently hot as @#$% in my garage, so I haven't been working on the lathe much. Until I was in my 30's I had skilled labor jobs, and never an air conditioned one. Now that I'm in my 60's I don't know how I did it.

Anyway, after some trial and error I have managed to get the spindle considerably freer, although still not free. Not too bad dialing in the 4 jaw now. And I'm getting a really good finish. And it's running about 20F degrees cooler. All in all it's much improved.

But the main reason I'm posting is to acknowledge those of you that said 140F degrees wasn't too hot. I Googled "bearing temperature" and it seems for many bearings 140F is on the low side. And I also found that bearing lubrication temperature limits is the main concern. Heat is going to burn up the lube way before it overheats the bearings.

So anyway, that was an epiphany for me. I'm no longer worried about how hot it's running.

What's normal:
The role of temperature in bearing applications | Evolution Online