Lathe is cutting a taper

Yep it appears to be the bed, now I'm back to screwing around trying to get my own lathe to cut, thanks guys :)
 
Unless that lathe has tens of thousands of hours on it and was never lubes or had ways clean I have a hard time believing you have enough way wear to cause .200" variance end to end on work piece. In my way of thinking that lathe would have to have soft ways and been seriously abused to be that bad in the wear dept. I would do the two collar method, dialing tailstock in to get both collars to be within a thou or two, nothing fancy there. Then turn the whole piece end to end with a light cut , positive rake, sharp HSS bit, and see how big a saddle or hump there is in middle if any. .200" is a ridiculously large amount to be bed wear or saddle wear. I have seen more than my share of clapped out lathes, and turned on a few, never seen one that bad, I am betting you have a seriously out of position tailstock, or wrong tailstock, or bent tailstock ram, something is way out of wack and I would bet money its the tailstock.

Squeaking and intermittent cutting at beginning of cut would lead me think you may have the tool bit too high, maybe dull or very negative rake. You may have a combination of issues. I would rule one out at a time, make sure you have a nice positive rake tool bit, set on center, (use the trapped ruler method to check if that is all you have it works fine) after you know you have a good cutting tool then tackle the tailstock dialing in.
 
+1 for what doubleboy said. .200 taper in 12" is more than a lot. Bed wear may be an issue, but Iam guessing something else is the real culprit.

Please tell us how you set up the round stock to be cut. For example, Did you hold between centers, and use a dog to drive the shaft? Or hold one end in a chuck, supporting the tail stock end with a center?? If the shaft was held askew in a chuck, the far end of the shaft could easily be out .250" at the tailstock.

Also, for example, has the headstock ever been removed and re-bolted back on? The machine rebuild guys will say the headstock needs to be carefully tightened back down with uniform torque - or the headstock axis will tilt - Imparting taper. So lots of other things could be contributing to your taper. Most are easily fixed, it's just discovering what's going on that can be the hard part. Flustered

Glenn
 
More info about the setup that caused the taper is needed. Was the stock held in a chuck, collet, or driven by a dead center + dog? If a chuck, what kind? What end was the large end of the taper -- the headstock end, or tailstock end? Is the taper reproducible if you turn a test piece or two?
 
Like I said guys, it was the bed, my dad just dropped the thing off in the corner of his garage over a large crack and it was slightly twisted, between that and the tailstock being offcenter appears to have done the job.
 
Metal said:
Like I said guys, it was the bed, my dad just dropped the thing off in the corner of his garage over a large crack and it was slightly twisted, between that and the tailstock being offcenter appears to have done the job.
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Thanks for the update, which could help others with similar problems. Closure is good.
 
I got the taper down to like 5 thou, the threads on the adjustment for the tailstock are really course so I ran out of patience, i'll hit it again in a few days :)
 
Search on making a spool for a 2 collar test.

Simple to make and you adjust as you make it.

Once made you use a dial indicator in place of cutting tool and adjust until zero.

You just need a chunk of round stock about 3 inches long by 2 inch diameter.

Sent from my SAMSUNG-SGH-I337Z using Tapatalk
 
If the bed is twisted, isn't it possible you could adjust the tailstock end to match the headstock end, but still have variations in diameter along the length of the piece?
 
homebrewed said:
If the bed is twisted, isn't it possible you could adjust the tailstock end to match the headstock end, but still have variations in diameter along the length of the piece?
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Yeah that is exactly what the story was, the tailstock was lined up but it was still cutting a taper which was a head scratchier.
just shimmed up the feet and all set! (after redoing the tailstock)
 
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