Seized Spindle

SamI

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So I was working away this evening turning some aluminium, around 40 mm diameter. Whacked the lathe up to full tilt and had at it. No problems here.

After the third part I went to part off when the lathe, without warning siezes solid! WTF?! I barely touched the parting tool to the work!

Anyway, long and short of it is my headstock is in pieces now luckily nothing seems to be broken but it is not a simple affair to disassemble.

The lathe is a Warco GH 1330 which I believe is the equivalent to some of the PM Taiwanese machines.

I believe I have traced the source of the failure but thought I’d ask for feedback here.

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See the aluminium collar around the spindle? I’m pretty sure it’s this that has siezed. Now the assembly has cooled it now spins freely although does stick if you wiggle it.

I’m pretty sure that the oil drains through this channel in the top and into the bearing.

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You can see this seems to be the prime spot for debris to accumulate. The actual gearbox is pretty clean inside as is the oil. Or was. Most of it is now covering the workshop floor.

Looking back at the front end, the oil drains down into the spindle bearing and the aluminium collar seals it in. What I believe has happened is that debris carried in by the oil has accumulated around this collar which, when span up to full speed caused it to expand and seize.

Looking at it and it appears to be a bit of a sump, a natural place for debris to settle. Has anyone come across this before? The lathe is a little over 18 months old and has had one oil change in the time I’ve had it. It is due another but not overdue.

Other than increasing the oil change schedule does anyone have any other suggestions? Maybe a magnet in there to trap any metallic particles? I’d be worried about it becoming dislodged though.

I’d love to hear your thoughts on this.
 
I put magnets on the bottom of my gearbox same style as yours. I figured debris would settle. I wouldn’t think that the clearance from the collar to spindle would be that tight? Maybe try putting some oil there and run it and see if problem persist. Did spindle move before you disassembled?
 
No, spindle was siezed solid. Could barely rotate it even using the chuck key in the chuck as a lever. As it cooled it gradually got easier to turn until, at room temperature it appears to spin freely (in its part disassembled state). Note it doesn’t get hot to the touch but quite warm in use.

The collar doesn’t have a lot of wiggle room and only since giving a fair bit of wiggle has it freed up to what I would call acceptable. Also, if you slide it back there is evidence of some silt gathering around there which has caked onto the spindle.
 
Right, a quick update.

After many hours I’ve got the spindle out! Would have been a much easier job if I had a big boy set of circlip pliers!

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So you can see in this shield the channel for oil to flow and the milled bit at the bottom appears to be a sump to collect debris.

On the spindle itself I found two spots where metal debris has welded itself to the spindle. I started filing before taking this snap but it should give you the idea.

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Not that easy to see and to be honest I’m surprised that this was enough to stall a spindle. But I was able to isolate the bearings and there was literally nothing else it could be.

I’ll clean it all up and reassemble and fingers crossed it all works!
 
Finally got everything reassembled and thought I’d give a quick update in case anyone else comes across a similar issue. I’m beginning to think that the issue may have been down to over tightened bearings.

Upon reinstalling everything I decided to do a “proper” spindle bearing adjustment. I tightened them to as close to 0 play as I could get ( less than 0.01 mm, probably around 0.005 mm) but the spindle was pretty stiff to turn. I backed them off until the spindle span freely by hand in neutral. I warmed it up at 400 rpm for 5 minutes then whacked it to 2000 rpm (max speed) for another 5 minutes and re checked. The spindle was pretty stiff to turn by hand and if I stuck my fingers in the back of the spindle bore it was hot to the touch.

When the binding occurred I had been doing a run of parts at 2000 rpm which is something I’ve never really had to do before. It is probable that it was thermal expansion that caused the binding after all that.

So after all that all I really needed to do was to go and have a cup of tea and come back to it!
 
Right, a quick update.

After many hours I’ve got the spindle out! Would have been a much easier job if I had a big boy set of circlip pliers!

View attachment 292912

So you can see in this shield the channel for oil to flow and the milled bit at the bottom appears to be a sump to collect debris.

On the spindle itself I found two spots where metal debris has welded itself to the spindle. I started filing before taking this snap but it should give you the idea.

View attachment 292913

Not that easy to see and to be honest I’m surprised that this was enough to stall a spindle. But I was able to isolate the bearings and there was literally nothing else it could be.

I’ll clean it all up and reassemble and fingers crossed it all works!

That's more than enough to seize a rotating mass that size. I used to build racing go-kart engines and saw seized main bearings all the time.
 
Stick a few rare earth magnets on the outside of the cover. The magnetic field will transfer through. They won't have huge holding power but you really don't need to hold everything, just move it to a different path so it isn't going straight into the channel loaded with metal.

If it were me I would look at the gears inside and put the magnets close to where it appears they do most of their slinging. You want to avoid putting them near the channel as they will gather any iron and eventually block the oil path to the spindle. And they won't do anything with bronze so may not solve the problem entirely.

You just have to look at this and realize that someone long ago recognized that they could harness this power and created friction welding. As I recall the rpm's in friction welding are similar to what you were working with on the low end.
 
I put magnets on the bottom of my gearbox same style as yours. I figured debris would settle. I wouldn’t think that the clearance from the collar to spindle would be that tight? Maybe try putting some oil there and run it and see if problem persist. Did spindle move before you disassembled?
This sounds like a brilliant idea. As long as the magnets stay put.
 
This sounds like a brilliant idea. As long as the magnets stay put.

That's what I'm worried about. I chucked a few in anyway and will just have to keep my fingers crossed they don't end up getting flung somewhere they shouldn't!
 
That's what I'm worried about. I chucked a few in anyway and will just have to keep my fingers crossed they don't end up getting flung somewhere they shouldn't!

Just don’t use cheap/weak magnets. I put neodymium magnets in mine. Takes considerable effort to separate.
 
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