Repair/Replacement of Eccentric Lathe Spindle on Homebrewed(?) Lathe?

[Jeff Wayne]

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Direct knowledge of this lathe died years ago with owner. The turning is undesirably eccentric, and it would be very nice to fix . . . if possible, on a blue-collar budget.

The motor—separate unit, driving a belt—is badged both "GE" and "Universal Fan Company".

The two bearings in the headstock have been replaced, (and unfortunately, that didn't solve the eccentricity). The larger of the two had a 26mm inner diameter which an old hand at the bearing warehouse found odd: he guessed the original bearing was from an automotive application.

http://i61.tinypic.com/91atdh.jpg

http://i62.tinypic.com/2zqg26a.jpg

http://i60.tinypic.com/zmjvbt.jpg


The tool rest and tailstock look more commercial, but I've not noticed any brand markings.

http://i60.tinypic.com/25pigk4.jpg


Do the headstock and spindle look completely home-cobbled?

Any ideas for replacement or even coarse repair of the spindle?

[Dennis Ford]

The headstock is definitely home-made and is ugly but that does not necessarily mean it is bad.
The first task is to determine what the problem is, then what is causing it.
When you wrote "The turning is undesirably eccentric"; did you mean that the wood ends up out of round?
If so; are you using both a chuck and the tailstock? Alignment is not likely to be perfect on this lathe and that might be a problem.
If the wood ends up out of round and you are not using the tailstock; something is loose that should be tight. Possible causes:
* Bearings do not fit tightly into headstock
* Bearings do not fit tightly onto spindle
* Chuck does not fit tightly onto spindle (this would be my guess)
* Headstock is not tightly secured onto lathe

If you can identify the problem AND have a machinist friend; any of above can be fixed.
If you have to pay for the trouble-shooting and machinist work, it will cost more than this lathe is worth.

[Jeff Wayne]

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Ugly can be lived with :) . . . especially if there is a payoff in utility.


When you wrote, "The turning is undesirably eccentric", did you mean that the wood ends up out of round?
Yes, oval rather than round, with and without use of the tailstock.

The newly installed bearings seem snug in the headstock and quite tight on the spindle. The collar insert the SuperNova2 rides on appears to make a firm fit. I'm inclined to think the spindle is bent.

Thank you for the reply and the points to ponder. I'm sure your cost calculus is correct.

[Marvin Hasenak]

Have you tried turning the shaft by itself without the chuck on it to see if it "looks" like it is turning true? From the way the end of the shaft is buggered up by what looks like a set screw it would be my guess that the chuck is not centered on the shaft.

[Dale Miner]

A bent spindle, or an off center chuck will not make the piece eccentric. If the spindle is tight in the bearings, and the bearings are tight in the housing, then the axis of rotation of the spindle will be true regardless of the straightness of the spindle or the squareness of the chuck mounting.

There would be issues with the ability to remount a piece and have it run true with a bent spindle or an inaccurate chuck mounting, but you have not described that issue.

Your pictures show what appears to be a set screw mounting method for the chuck or faceplates. If there is clearance between the spindle and the bore of the chuck, then as the spindle rotates, the clearance allows the chuck or faceplate to move while the piece is being turned. This will result in an eccentric turning. But, with the tailstock in use, the eccentricity in the turning should become virtually zero at the tailstock end, and should be somewhat improved at all points in the piece.

Your photos show what appears to be substantial wear on the chuck mounting end of the spindle. If that is the case, I suspect it is the source of your problem. If you have the spindle reworked, my suggestion would be to do away with the set screw mounting and have a typical threaded mounting.

[Jeff Wayne]

Your photos show what appears to be substantial wear on the chuck mounting end of the spindle.
Yes. I'm surprised the spindle steel is that soft. I could clean it up some, but I'd expect diameter reduction to worsen the problem.

Thanks.