What am I doing wrong?

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ReverendThom

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My pens are not turning perfectly round. I use between center mandrels and they meet up perfectly with one another. But all of a sudden my turnings are out of whack. so while one side of the pen is flush with the bushing the other side can be a millimetre or two higher. I don't understand. I have not experienced anything like this in two years of turning.

Any ideas? Somehow something to do with my drilling? Something to do with my facing? I've tried putting the tail stock tighter and I've tried it looser and neither seems to help
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I would like to see a wider shot of the whole blank showing how you have this mounted. Could there be some slop between tube and bushing?
You mentioned between center mandrel. I'm confused about that. I either use a mandrel, or turn between centers with bushings. Could use more pictures and information.
 
From the pictures, I cannot tell much. It looks as if you are using bushings. If that is the case are they the correct bushings. that is do they fit snuggly within the brass tube? And, are you sure the bushing is held concentrically by whatever is holding it?

You mention turning between centers. I cannot tell from the photos if you are using 60 deg cone dead-center in the drive and a 60 deg live-center in the tailstock. Are they what you refer to as mandrels? Or are you using the PSI Mandrel Saver? Obviously something is out of concentricity - or as we say down here in Mississippi, "something's outta whack."

DrD
 
Dalecamino said:
I would like to see a wider shot of the whole blank showing how you have this mounted. Could there be some slop between tube and bushing?
You mentioned between center mandrel. I'm confused about that. I either use a mandrel, or turn between centers with bushings. Could use more pictures and information.
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Sorry, they call it a between center mandrel. Picture attached.

It's the right bushings for the respective kits. Had happened with both a Sierra twist and Virage ballpoint kits.

Ah! A bit of stream-of-consciousness going on here. You both got me thinking now and the one thing in common with these kits is they use the same size drill bit and I felt when gluing in the tubes that the drilled hole was just a bit too big for the tube ... The tubes just weren't quite as snug as other kits' tubes are usually. Maybe my 27/64 bit is just a bit bigger then the tubes? A little bit of space between the tubes and wood maybe. I am away now but will take a look later.

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As long as the tubes are glued and seated in they should still turn round to the tube.
Have you checked each bushing with calipers to verify they arent out of round on the outer portion.
Possibilities could be out of spec bushings or off center tailstock alignment or brass tubes shifting a bit inside blanks when turning are what comes to mind.
 
Ok, so you are not using the PSI Mandrel Saver, but their version for turning between centers. Have you checked the fit of the kit bushings on each of the PSI stub mandrels on their dead center and live center? And, are you sure the taper on each of the PSi pieces is the same as the corresponding tapers on your lathe, i.e. all are either MT 1 or MT 2? Please don't take offense at these elementary questions - we're just doing a modified Ishikawa process to check possible causes.

DrD
 
How snug is the bushings on the mandrel centers? Any slack at all? How snug does the bushings fit into the tubes? Any slack "can" cause this
 
I had the turn between center mandrel system also. Had the same problem on the tail stock side. Measured the run out on the shaft where the bushing goes with a dial indicator and it was severely outta whack. Have not used it since and haven't had that problem again.
 
drise said:
I had the turn between center mandrel also. Had the same problem on the tail stock side. Measured the run out on the shaft where the bushing goes and it was severely outta whack. Have not used it since and haven't had that problem again.
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That would have been my guess.
 
As many have suggested, place in between your centers, turn, and see if there is an lathe-centers alignment issue. Also ensure that the tube is free of debris. If you lathe is true, that is a big headache not to have to worry about. I would also make sure there i snot play in your tailstock after completely locking it down.
 
I agree with all that is written above, lots of good info. Just to be a smart A$% though, maybe you're not holding your mouth right? Sorry, I just couldn't let that one go. I sure hope you figure it out and can get some nice results.
 
Could be bushings or mandrel. Two quick tests:

1) Maintain blank orientation and swap bushings end to end. Turn the blank some more, if out of round reverses ends blame the bushing.

2) Flip the blank maintain bushings in their respective end. If the out of round swaps ends the it a problem with the mandrel or tail stock.
 
Mount the tailstock "mandrel" into the headstock and power it on. Does it run true? Or is the "mandrel" off-center?

If it is correct, then mount on tailstock again and turn by hand to see if it wobbles. If it does, there is "stuff" in your tailstock morse taper.
 
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