I was turning a 2 1/2 shaft by 4.25 in. down to 2 in. I turned half of the shaft down to size then did the other side but they did not match where they joined. the second halve was over cut on one side and under on the other side. hope I said this right so you guys understand. Would you say it is the head that is to one side or the chuck. The lathe is a KBC Taiwanese lathe, it seems to be adjustable but not shure . There are two bolts under the chuck that bolts to the base, and two set screws on the back side cant see any on the front or the back of the head stock. That dosent look like I could ajust from there or what do you think. Hope this makes sence to you all? Thanks Denis
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head or chuck misalinged
- Thread starter Deny1950
- Start date
Makes perfect sense and there's nothing unusual about it at all. It's next to impossible to pull-off a cut like that and expect it to match perfectly and I avoid that kind of cut completely.
In all probability, the piece was not held straight in the jaws. Next time you chuck-up a shaft, put the dial indicator (DI) one inch from the jaws and center the piece. Next, move the DI a couple inches down the shaft and read it. It will almost certainly show a good bit of variance. 5-10 thou is not surprising at all. Why? because the jaws are not holding the piece perfectly perpendicular to the face of the chuck. You can square-up the jaws to minimize the problem but, it's next to impossible to make it perfect 100% of the time -and the reason is because the jaws ride in slots in the body of the chuck and there's unpredictable amounts of wiggle.
Using collets will help -but there are no collets (that I know of) in that size range.
The ultimate solution is to use a piece of stock long enough to make a cut the length you need then, chop off the unused piece.
Ray
In all probability, the piece was not held straight in the jaws. Next time you chuck-up a shaft, put the dial indicator (DI) one inch from the jaws and center the piece. Next, move the DI a couple inches down the shaft and read it. It will almost certainly show a good bit of variance. 5-10 thou is not surprising at all. Why? because the jaws are not holding the piece perfectly perpendicular to the face of the chuck. You can square-up the jaws to minimize the problem but, it's next to impossible to make it perfect 100% of the time -and the reason is because the jaws ride in slots in the body of the chuck and there's unpredictable amounts of wiggle.
Using collets will help -but there are no collets (that I know of) in that size range.
The ultimate solution is to use a piece of stock long enough to make a cut the length you need then, chop off the unused piece.
Ray
Ray covered it, but I'll say it simpler. 3 jaw chucks, as a rule, won't repeat well enough to flip-turn a part unless you have bored soft jaws or a set-tru style chuck. Even a brand new chuck is not guaranteed to run that true. If you're careful, with a little brass tapping, you can do it, but it's a matter of experience and finesse.
Thanks for the good advice.
I have to ask this as a new to turning guy........if you turned it between centers (you could make a dog pretty easy) and your tail stock was aligned close wouldn't this allow you to flip the work piece.
Probably not the best way, but seems feasible to my untrained mind.
Probably not the best way, but seems feasible to my untrained mind.
Yes. Even if the tailstock was not properly aligned, the step would be minimal, only if there was a taper because of the ts misalignment, not an issue with concentricity. Ideally, that would be the way to get a true shaft with accurate center holes on both ends.
Dennis
The steps I usually use is to first put the stock in the lathe sticking out about one or two inches. I drill a short hole in the center with a countersink bit. Re-chuck my stock to length adding my tail stock with a live center, I then insert the live center into the material. Lock it down and ready.
I hope this was helpful.
Bob
The steps I usually use is to first put the stock in the lathe sticking out about one or two inches. I drill a short hole in the center with a countersink bit. Re-chuck my stock to length adding my tail stock with a live center, I then insert the live center into the material. Lock it down and ready.
I hope this was helpful.
Bob