Out of round between centres

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keithkarl2007

keithkarl2007

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I got a new axminster variable speed lathe over 2 months ago and have only started using it as i was waiting for pen mills and other stuff to arrive. I purchased a dead centre, live centre and bushings from JohnnyCNC hoping it would make life a little less painful but i'm still having trouble turning out of round. I just don't know what the problem is. I've tried going back to the mandrel and thats worse. It has me really frustrated as I've bought a load of pen kits and blanks in the past few months. Any ideas???
 
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Your head stock and tail may not be aligned. You can realign your headstock fairly easily. You could also be tightening your tailstock too much, also remember to take light cuts, without too much pressure.
 
That small difference will make your turned blanks out of round. I would correct that or contact the dealer about it and have them help you. I would also check the head stock and see if there is dirt underneath the housing and clean it out. They should align evenly or you will continue to encounter problems.
 
keithkarl2007 said:
yeah i will try that, if that doesn't help would i need to shim up the tailstock
Click to expand...

On a new machine, I would not do that. Take it back to the dealer and have them FIX. Grind down rails under headstock would be one way, but that's NOT your problem on a new machine.
 
i know ed, its still under warranty but it'd cost me a small fortune to ship it back to the uk. thing is i've only used it twice and thats when i noticed the problem
 
Keith,
What kit is it you are turning and having the problem with?
Can you give us a few more details on how you got the blank ready,
including trimming the ends,cleaning out tubes,etc?
and how you are turning it, such as what tools,how sharp are those tools,etc?

Have you turned any/many pens before this new lathe?
(Hate to ask that one, but you have (0) photos in your album..)

I'm sure there is a solution, it is just such a broad issue at this point,
with so many variables,let's try the process of elimination.
Like Mudder was asking for someone to write an article on out of round, and
I thought about it, but to cover every base in detail would require volumes
of writing, or so it would seem.
Thanks,
John
 
If you are using bushings they can be drilled off center. I had one 10 thou. out. I t made the pen out of round. I had a machine shop drill the hole larger which makes it necessary to turn between centers.
 
i was turning a sierra with the bushings and equipment i got from you, i drilled the blank on my pillar drill glued in the tubes when dry i cleaned the inside with a small craft knife before trimming the ends. Your stuff is sweet by the way, those bushings are a lovely snug fit compared to others which have a little play in them


johnnycnc said:
Keith,
What kit is it you are turning and having the problem with?
Can you give us a few more details on how you got the blank ready,
including trimming the ends,cleaning out tubes,etc?
and how you are turning it, such as what tools,how sharp are those tools,etc?

Have you turned any/many pens before this new lathe?
(Hate to ask that one, but you have (0) photos in your album..)

I'm sure there is a solution, it is just such a broad issue at this point,
with so many variables,let's try the process of elimination.
Like Mudder was asking for someone to write an article on out of round, and
I thought about it, but to cover every base in detail would require volumes
of writing, or so it would seem.
Thanks,
John
Click to expand...
 
Keith,
Thanks for the reply,
If Sierra, I'll ask..how did you trim the blanks? Using trimmer set?
I don't know of any sets that include a Sierra pilot. Do you have one
that fits correctly. if not, blank ends just a bit out of square can lead to
all sorts of headaches.
Did you notice any bad vibration while turning?
 
Well, I won't go into the OOR discussion. Out of concentricity is the actual term, but anyway, to have the problem with between center turning I would think could be either ends not being perpendicular with the tubes, or something causing the dead center in the head stock to run out. Too much tool pressure can be an issue as well, but that can also cause the blank to spin, so. ...... I am not a believer in the head stock-tail stock alignment theory being an issue. If you were using fixed tools, like a metal lathe, you would have taper issues, but not concentricity ones. Now if it were way off, it can cause other issues, especially if you drill on the lathe.
 
i glued a slimline tube into a piece of scrap and turned it down to fit inside the sierra tube, even when i put just a brass tube between the bushings between centres i can feel the vibration



johnnycnc said:
Keith,
Thanks for the reply,
If Sierra, I'll ask..how did you trim the blanks? Using trimmer set?
I don't know of any sets that include a Sierra pilot. Do you have one
that fits correctly. if not, blank ends just a bit out of square can lead to
all sorts of headaches.
Did you notice any bad vibration while turning?
Click to expand...
 
I sense either the dead center is not running true in the head stock, or bushing issue. But having seen johnnycnc's work, I would doubt it is from bushings. If you can check the tapered bore of the lathe with an indicator, might try that as a starting point. You might just check the dead center while it is in the lathe before you take it out. If it is running out a bit, try to rotate it a quarter of a turn the pop it back in and check it. If better (or worse), do it again.
 
Could be that the hand wheel on the headstock end is not screwed down tightly. Mine worked slightly loose recently and it took me a bit to figure it out. Causes a very slight wobble on the headstock.
 
with just the dead center in place, turn on the lathe and watch the tip. It should be stationary, if it's making a circle, then the problem is in there some where (dead center, headstock spindle, bearings, etc.)
 
finally got a photo of it up, had a terrible shake in my hand
 

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Keith,
I checked your bushings (I do all of them) before mailing
on a known good lathe.They are good.
You mention having the problem on the mandrel also, and going
between centers with my bushings was better, but you are still
not there.
Sounds like a lathe or turning style problem that was there before
my bushing arrived at your door.
Try running the lathe with no centers, is there vibration then?
Then add the dead center, as has been mentioned, and check.
Put you mandrel in and see how much it wobbles,for reference.
Does the live center point turn fairly freely? is it noisy with something
driving it?
Are you keeping the tailstock quill retracted as far as practical?
they can get squirrelly when ran out too far.
Also, how sharp are those tools? do they cut at just a touch to the blanks?
If a little dull, you wind up pushing them, blank setup flexes under that pressure.And that pressure is not controlled, thus not even.

Just tossing out ideas here!
 
yeah my turning tools are sharp, i don't let the quill out too far. The mandrel that came with the lathe turned out of round, the new one i got didn't but when i bring up the tailstock it moves the mandrel but it seems to push it up rather than down, which it should if you look at the photo
 
EVery so often I spin an out of round pen on the Johnnie Bushings. Every time that happens, I pull the pen, run the points together and find they don't touch dead center. They are ok up and down, just get a hair off side to side. I've loosened and moved the headstock a hair and re-tightened the head and it works every time. I have discovered, or at least theorized, that the head becomes un-aligned over time from punching out centers. The punch isn't the same size as the hole, you are punching on one side or the other which can cause the head to turn a millimeter or so out of whack. I can't tighten the screws any tighter than they are without risking damage to them, so I just keep an eye on the situation.
 
The live center on my new JET lathe was quite out of center (when turned by hand it was well seen); I had return the live center to the seller. They said they have repaired it, but it was quite the same after returned to me.
So I went to old tool-master near me (he makes woodturning equiptment) and he made me a new live center, with 2 bearings and now it is OK.

I also had 2 mandrell rods - one running perfectly, the other was also out of center a little - but when the live center grabs in, it is OK also.

Hope you can help with anything above.
 
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