Out of center turns

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HeartofaPen

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May 16, 2010
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129
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Hockley, TX
I have had this issue in the past where when I am turning down a blank, on at least one end and sometimes both, the turn is not balanced, see pics. Not sure that is the correct term or not but wanting to know how to fix this. Haven't turned in awhile so not sure when it started but have had the same thing in the past. I made sure the head stock and tail stock align properly so not sure what to do.

Any help appreciated.
 

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I would call it out of round. It might be the mandrel is bent. You can try what was mentioned earlier and see if the problem moves to the other side or lay the mandrel in a flat surface and roll it to se if it's smooth.
 
I believe I recall a similar issue and ultimately discovered my blank was moving at times (radially between the bushings) while turning. Some sort of looseness when I chucked it between the centers but I do not recall for certain.
 
It looks like TBC bushings. If so, are you sure your blank is squared properly? If the end is not square, the bushing can turn out of round.

If that is NOT the problem, we are looking at the tailstock end, reverse the blank and see if the tailstock end still has the same problem.
That would isolate the problem, now leave the blank in the same orientation and switch the bushings--did the problem go with one bushing?

After all this, you have isolated either a bushing or one end of the lathe--then start to cure the problem.
 
That looks like the concentricity is off by about 1/32" or more. That is a lot.
Could be the ID of the tube is not clear.
You may have build up of CA on the live center angle,
Your live center bearings could be bad,
Is your bushing in the tube or just riding on the face?
Do your bushings fit loose to the ID of the tube,
 
A multiplicity of things can cause this. All but two are related to the mandrel characteristics. TBC, turning between centers will eliminate most.

Here is a thread that is not directly related but OOR is mentioned a few times as well as TBC.

If I had known this earlier . .

I am on a fact finding mission. Can you help? What do you wish you had known earlier in pen turning? or in different words: Knowing what you know now - IF you could go back and start over in pen turning - what would you skip, change or do differently? answers for instance: - I wish...
www.penturners.org

OOR (out of round - not "technically" correct but for laymen's terms, it works well). Is caused by:
1. a bent mandrel (even a minuscule bit)
2. tail stock pulled up too tight, forcing a minuscule bend in the mandrel as it turns
3. poor fitting bushings ( rather loose)
4. ends of the blank(s) not perfectly square or tube ends not square
5. slightly dull tools that require a bit more pressure to turn the blank down. Sharp tools are needed!!!!!! Let the tool do the cutting, not force/added pressure. This force - puts pressure on the mandrel causing OOR.
6. heavy sanding, particularly on softer woods. The softer wood between the hard ridges sand off quickly causing OOR.
7. Wrong Live Center in the Tail Stock. The mandrel has a dimple in the end that fits up to the Live Center of the Tail Stock. MANY talk stock live centers are much more pointed than the one that is actually needed. You MUST HAVE a 60° Live Center to fit into the dimple of the mandrel. IF NOT, the very pointed one - the very tip of the pointed one will ball up or bend (might need a magnifying glass to see it) and will cause OOR. Quite common for new pen turners.
8. Loose tail stock, not tight enough.

9. You have already checked tail stock and head stock alignment.

TBC will or can eliminate problems 1, 2, 3, 5, & 7, and in some cases 4. It Looks like you ARE using TBC, then the problem is loose bushings in the tube, or not square blanks combined with a lot of pressure, forcing it OOR/no concentric.

Second Thought, In Some cases, while the lathe will line up tail stock to head stock OK - they "can" be locked down out of alignment in some cases. Might be yours
 
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Thanks for the feed back. I will try some of the suggestions when I get back to the shop later today. This is a new kit for me, a seam ripper and first time using the bushings. I have had the exact same thing in the past with several other pen kits on both my MIDI and Full size lathe. I square all of my ends on the drill press using the barrel trimmers and never had a problem at first. I did find that my Drill center vice was out of square so I quit using it and now getting straight drill outs and I believe trimmings. It also happened when I would use the adjustable mandrels.

I will see what happens and let you all know.
 
OK, I have dome the suggested and here are is what happened.

The first one came out good. Perfectly round the tube inside in all proportions and have already delivered it to client. The second one, I just did this morning, waiting on more tube since I ruined a couple. It also came out OOR. As for the roundness, it is perfectly round it is jus there is more wood on one side of the tube than the other. I have been having issue with when drilling in my drill press that it not always drill straight through. I thought it was my drilling vise so I went back to a different vice I had and thought it resolved.
Well, on the one from today, when I drilled it, it was not a straight through drill. The bottom hole was off center to the starting hole. A couple other blanks I drilled with the same setup were al but perfect. I am picking up more tubes tomorrow to try with these.

My question is, can when drilling and it drills in an angle instead of straight through, can that cause this OOR to happen? I am setting up to try and drill from the lathe which I have not done before but have had what I needed for awhile.
 
It also came out OOR. As for the roundness, it is perfectly round it is jus there is more wood on one side of the tube than the other.
Click to expand...

Technically, OOR is not correct, but it is used more in the vernacular and rather going into a sentence long explanation every time, we just use the term OOR. But as you noted - it is not OUT OF ROUND because it IS round. The problem is that It is not concentric to the center of the tube. That signifies a different problem. I don't think it is related to the drilling itself. If the drilling is straight regardless if going through at an angle, a straight through hole will not cause it. The problem WILL show up with the blank not being squared on the ends to the tube AFTER drilling.

Now, if you square the blank, drill at an angle and don't re-square the blank perpendicular to the tube, that can certainly cause that.

WAIT! I just looked closely at your pictures. The bushings should be up inside the tube to the bushing's shoulder. They are not in that picture above. You are probably using the wrong bushings. The picture of those bushings show the bushings with a shoulder. The shoulder should fit up to the tube. Or are my eyes imagining things?
 
leehljp said:
WAIT! I just looked closely at your pictures. The bushings should be up inside the tube to the bushing's shoulder. They are not in that picture above. You are probably using the wrong bushings. The picture of those bushings show the bushings with a shoulder. The shoulder should fit up to the tube. Or are my eyes imagining things?
Click to expand...
I just looked again, and I think you're right.
 
Not sure that I was able to resolve the issue yet but was able to get 4 seam rippers finished. One the last 3, I would turn to the bushing on the head stock side then turn around and do the other. Sanding was not an issue after that. I will post picks in the other items turned forum.
 
I now turn most of my Pens between centers living in the UK if you go to the PROKRAFT web site you will see an excellent video on how to do this. You still use bushes but mount between centers. This allows you to take the turned wood off the lathe as many times as you like and it always goes back in the same place and runs perfectly true.
Pen Mandrels will never allow this much accuracy. Hope this was helpful.
 
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