new lathe wobbling off center? does it even matter?
Hi everybody, I recently purchased my first lathe: the excelsior mini-lathe from Rockler. After turning my first pen, I realized that the turned blank wasn’t true: it seemed to be round, but off center. I know I didn’t tightened the tail-stock too much, so I borrowed one of these magnet calipers, and it seems to me that the head -stock’s shaft is not running perpendicular to the head-stock. (basically, it wobbles). I’ve attached a picture so you can see how I’ve measured the offset. just to make sure I also took measurements from the inside taper, the face plate (not shown), and even the mandrel and its shaft. in the location shown in the picture the offset was about .006″ What do you think is the problem, and more important, should I bother trying to fix it or just send it back (major hassle)? my guess is that the machine is poorly build and either the bearings’s seats are not parallel or the bearing themselves are cheap. however there is no play, and the offset is quite smooth, no jump or step. please keep in mind that this is my first lathe and I’m sort of learning this on my own so maybe I simply missed a simple set-up! Any advice will be greatly appreciated. Thank you!
Replies
not that it may be offset there where you have the dial indicator but that it may be out of round or that the bore (taper) is not bored perpendicular to the outside. where the alignment problem shows up is that the headstock shaft is not in alignmrnt with the tailshaft.
there are no standards for this except for an old military
standard that at 12" from the headstock that alignment should be within .005"
ron
As mentioned in previous post. I would use the Dial indicator on the inside to the spindle. That will give you a true indication of where the problem is.
But on the ergonomic side, an Oval pen can be comfortable to hold.
well, as I said, I don't
well, as I said, I don't think the turned pen is oval. but the center of the outside diameter is not the same center as the inside brass tube. maybe it is oval, I don't have the pen handy ( I gifted it to my father-in-law) but I'll try to measure it with a caliper.
I have measured the inside taper offset as well.
THere is a wobble there as well, although it's much smaller: not only because it's closer to the center, but because the dial goes in at an angle.
thanks for reading.
PS I purchased this machine almost exclusively for pens, so perhaps I'm more "bothered" by small offsets?
it is if you are trying to drill a hole from a chuck mounted in the tailstock. if they do not align the drilled hole would be off centre. to meaure this put on a face plate and check it fot trueness with the dial indicator. if it is true then mount the magnetic base of the dial indicator to the face plate and then dial in the tail shaft to see if it runs true to the spindle in the headstock
ron
It's not answering your
It's not answering your question, but related: I've found that the pen mandrels secured by a single set screw in the side of the morse taper, by nature, create run-out. At first, I always turned the blank ends one at a time when they were against the live center, which ensured they were concentric. Then I dumped the morse taper holder for the mandrel and switched to a chuck.
studioso, is it possible that you are overtightening the tailstock and bending the mandrel?
well, as you can see in the picture, the head shaft's is wobbling too, and all measurments I've taken without getting the tail close at al.
and no, the pen wasn't oval: it was eccentric: the brass tube and the pen outside's diameter have different centers.
This forum post is now archived. Commenting has been disabled