I am having a problem that I I need some advice about. My Nova 3000 doesn't seem to be turning things round. If I turn a pen, and get the blank down to the bushing on one side of say the nib end it will be sticking out on the other side. If make a box the mating ends will be flush on one side and the top will protrude slightly on the other side. I am probably not explaining myself very well but it seems as though I am turning an eccentric circle instead of a proper circle. I checked the run out on the headstock with my dial guage and there is a 3/1000th difference. Is this enough to cause this problem or is there something wrong with my technique? Thanks for the help.
As far as the pen goes, you may be turning it round, but not centered on the insert. Is the pen mandrel straight? The long rod on the pen mandrels are easy to bend. measure the rubout at various points along the mandrel.
As a returning turner, I've forgotten so many basic things like that after years of not having room for my shop.. thanks for refreshing my memory, I'll check that alignment tonight!
Either the plank is not centered, which I doubt if you do not have trouble with other items, the mandrel is bent or your hole is not perfectly straight. If your drilled hole is off to one side the results will be what you are experiencing.
Since you didn't tell us how bad the run-out is at the far end, it's tough for us to do the trig and see if this accounts for the error. The error is multiplied based on the distance away. Consider that, starting at some earlier point in the head (most probably from the bearing at the far left of the head), you have a right triangle where the vertical leg is .003" away from the center line of the bearing at the point you took your measurement. If you extend that line on out to the end of the workpiece, you'll get the total error induced by the slop in the bearings. If this closely approximates the error you are observing, you've found the culprit.
As a point of interest, I keep reading very good things about your model of lathe, but given the price of that lathe, .003 run-out seems like an awful lot. I would expect the run-out to be more on the order of .0003 -- but that might be because I haven't completely changed over from the expectations of a machinist.
I missed the beggining of this thread so appologise if I have misunderstood the question, and my contribution has nothing to do with the 'problem'. Whilst the truer the lathe runs (least runout) the better it is, this is not going to prevent an object from being turned truly round. After all, in ofset turning, an item could be several inches off centre and still be turned perfecly round, so a few 'thou' runout is certainly not going to stop this from happening.
If the tailstock centre is not perfectly inline with the headstock it also is not going to prevent a parallel piece from being turned. Afterall unlike a metal lathe the toolrest travel is not kept in fixed alignment to both the headstock and the taistock. In woodturning, we move the toolrest/banjo as we wish, with no need to maintain any particular reference to the centres, only to the work. Close as possible without letting the timber hit the rest.
The most concern I would have with headstock/ mainshaft runout, is that it could cause vibration. This would become more severe as the speed increased. This would make it unpleasant to use the lathe and could even lead to producing a rippled effect while cutting. However this (rippled /corrugated surface) can even be caused by lack tool sharpness and technique.
My first lathe had a fairly obvious vibration (mainly caused by motor/ pulley errors) but I persevered and still could turn objects round. However if I had not experienced it myself I probably would not have believed how much better it was to turn on a lathe that did not vibrate. And how much easier it was to produce better finish on my work. (Unfortunately it did not make it more artistic :-( )
Cheers, Peter Stacey
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If this closely approximates the error you are observing, you've found the culprit.
With all due deference, I believe you are mistaken. Turn a dowel shape (round & parallel) in a piece of stock at least 6" long. Wipe it with contrasting stain (no need to wait for it to dry). Now offset the tailstock by a small amount. Recut the piece. If you move your cutting tool parallel to the centerline of the lathe until you just barely clean up up to the midpoint of the spindle, I think you'll find that one end is a cone and the other is lopsided.
If you can follow a spindle that is wobbling around the centerline (rather than revolving around it) and cut it both round and parallel, you are a far better turner than I.
Bill
PS: Being a better turner than I is not that big of a challenge.
What he's saying is that runout is immaterial _between_ centers. Wood is compressible enough to take up a lot of difference. Non-spindles are another matter. There the unconfined end is free to wander, and you to chase it.
Peter's example is of a standard turning trick, where _both_ centers are moved on the same vector for the same distance. This produces an oval turning.
Your example is also a technique used by yours truly on his mushrooms, so a cap parallel to the "ground" can sit on a slanted stem. Sometimes I use both, so I have an oval cap.
--------------------------------------- "Anonymous" I entirely aggree with you on this point "If you move your cutting tool parallel to the centerline of the lathe" However, seeing that there is no reason to restrict oneself to having the cutting tool travel parallel with the centreline of the lathe, (after all, is this not the way most spindle turning is shaped?) there is nothing to stop one from turning a true parallel dowel irrespective of how far the tailstock may be out of line. Like the exact oposite of turning a taper, on a lathe that has the tailstock in perfect alignment? All that needs to be done is to move the tool /toolrest to be parallel to the centreline of the WORK, NOT the BED. Cheers from 'Down Under' Peter Stacey.
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