Help! - Out of round -- bad bushing?

[JimMc7]

I'm getting my 1st occurrence of noticeably "out of round" with the cap on Baron pens and I'm asking for any suggestions to try to fix.

I think it may the bushing (or could be the small left spacer after I looked at the photo). I get an ~14 thou concentricity variation on the left side of the cap (you might see the color variation in the photo). I don't have this problem on other pen types using this same mandrel.




Things I've tried already (using the same procedure to tighten the tailstock & mandrel nut where applicable):

1. Checked the mandrel -- ~2 thou variance -- think that's ok
2. Checked the bushings-only installed on mandrel -- ~3 thou varance
3. Checked the bushings and tubes w/o blanks -- ~3-4 thou most places but did vary ~7 thou on the left edge of the cap tube (the problem spot!)

Things I'll try next:

1. Remove that small left spacer -- maybe not square on the end and left bushing is twisting a bit when tube-only or tube w/blank installed (more force on outer edge of bushing)? A bit of slop in the bushing might make this worse. Sorry, should have tried this before I posted but didn't think of it until I looked at the photo.
2. Buy new bushings.

I'd appreciate any other suggestions. Thanks!

 

[leehljp]

Jim,

1. Is that a 60° live center? My eyes are not what they used to be but that doesn't look like a 60° live center to me. IF not, that would be the first thing that needs to be changed. The standard L-Centers that come with wood lathes are not meant for mandrels and it often causes enough wobble on the end that results in your problem.

2. Over tightening the tail stock to the mandrel can cause the problem also.

3. Over tightening the mandrel nut if the blanks are not square - will jam them up and can cause some OOR problems, IMHO.

 

[randyrls]

Jim; Check that the blank ends are square to the tube inside them. I had OOR problems until I figured out that tightening the brass nut was actually pulling the mandrel out of true.
I did a dumb stunt once. Some bushings are available for both 7mm and 8mm mandrels. I believe the Baron is one of them. Make sure you are using the correct mandrel.

A quick test for OOR is to lay a lathe tool across the bushing while the lathe is running at slow speed, and feel for any bounce or vibration. Only touch the bushing and not the blank. It will be immediately apparent if there is any OOR on the bushings.

 

[dntrost]

Another thing to try is it appears you are using an adjustable mandrel. Shorten the mandrel so it is the size of only half of the blank and try to turn one half at a time. I found this helps. Others will say get rid of mandrel and turn between centers. I have not yet gone to that but have started only turning one half at a time and have seen drastic improvement in OOR pens.

 

[JimMc7]

Hank & Randy, thanks for the suggestions.

The live center point is a 60* Oneway pen pilot point.

I use a pen mill and sleeves on a drill press to square the blanks so I think the ends are reasonably square to the tube -- same process works for slimlines, Sierras, Cambridge, keychains, Jr Gents and the Baron pen portion tube -- only having a problem with the Baron cap.

Another fact: I rotated the left cap bushing 90* on the mandrel and tested bushings with tubes-only again. This dropped the variance to what I think is an acceptable 2-3 thou. Also helps explain the 1 good Baron cap I've done (previously posted Eugene bloodwood cross pen). I got lucky on 1 and not on the other 2!

Bushings are relatively cheap so I think I'll just try another set rather than driving myself silly measuring this set and wasting more material!

Thanks again for the suggestions.

 

[JimMc7]

Dion, good point -- I'll try that, too. I have shortened and done only one blank on slimlines when I get a bit of chatter -- although the chatter is usually on the blank nearest the tailstock rather than the headstock side in this case. Even with the mild chatter I don't notice the OOR like I do on this Baron cap -- I can feel the OOR "bounce" when I sand & finish.

Thanks!

 

[Wheaties]

Dion, good point -- I'll try that, too. I have shortened and done only one blank on slimlines when I get a bit of chatter -- although the chatter is usually on the blank nearest the tailstock rather than the headstock side in this case. Even with the mild chatter I don't notice the OOR like I do on this Baron cap -- I can feel the OOR "bounce" when I sand & finish.

Thanks!

That's what I was doing (shortening the mandrel), but I noticed it getting worse and worse the more I turned, and instead of going through a bunch of mandrels and fighting OOR all the time, I just said screw it and bought a live and dead center from John at PenturnersProducts.com. I would highly recommend you give this option some thought. I tried it out last night and OOR completly disapeared. Good luck!

 

[ed4copies]

Another thing to try is it appears you are using an adjustable mandrel. Shorten the mandrel so it is the size of only half of the blank and try to turn one half at a time. I found this helps. Others will say get rid of mandrel and turn between centers. I have not yet gone to that but have started only turning one half at a time and have seen drastic improvement in OOR pens.

I agree completely.

Also, try your number 3 with the bushings reversed. See if the runout is still the same. Will isolate, bushing or mandrel or some other "wobble" next to the headstock. (bad MT???????)

 

[jkeithrussell]

Get in touch with johnnycnc and get set up to turn between centers with his custom bushings.

 

[KenV]

"Another fact: I rotated the left cap bushing 90* on the mandrel and tested bushings with tubes-only again. This dropped the variance to what I think is an acceptable 2-3 thou. Also helps explain the 1 good Baron cap I've done (previously posted Eugene bloodwood cross pen). I got lucky on 1 and not on the other 2!"

Most excellent technique to use when approaching final shape or when using abrasives and finish. Will immediatly show if you have a "cocked bushing" or similar that is causing an off center turning effect. Have saved several items that were not working well. Magic marker reference is handy to approximate the 1/4 turn.

 

[RussFairfield]

Before looking for bad bushings and mandrels, have you looked at your sanding technique??

It could be too much sanding with too coarse a sandpaper. All wood blanks will have a difference in the grain directions around the blank and flat grain wood is removed faster with sandpaper than quarter grain.

A straight hard grain is the worst because it will go from flat to edge grain twice around the pen, and it is a situation that is begging to be made oval with sanding.

 

[JimMc7]

Zach, et.al., I have one of johnnycnc's CTC kits but no Baron bushings as I'm not all that fond of the Baron kit, anyway. Just trying to finish the few kits I have! Good point though, probably should just throw a few more $s in the pit (no offense meant for Johnny -- aimed at the generic money pit of penturning) and get the Baron bushings. Likely cheaper than wasting blanks.

Russ, I'm a newbie so all of my techniques are marginal at best! All of the Baron caps I've done are acrylic/alumilite. I noticed the OOR on the 2 failures at the 1st try of sanding so I don't think sanding technique is the particular problem here. Thanks for the suggestion in any case.

 

[JimMc7]

I bought new bushings and these seem to fix my OOR cap problem (of course, could be I just got lucky again with the new ones).

 

[Rifleman1776]

Try using the 'no mandrel' method of turning.
And, reconsider your source for mandrels. PM me if you don't understand.

 

[JimMc7]

I ordered the Baron CTC steel & Delrin bushings from John @ penturnerproducts -- shouldn't have to worry about OOR caps now.

As usual, great service, fast shipping, IAP shipping discount and a couple of free blanks from johnnycnc -- thanks!

 

[OKLAHOMAN]

Take a real close look at the where the tube meets the blank. If your hole is OOR at the ends and the blank and tube have some space between them on one side, your going to get OOR on the ends .

 

[heinedan]

My suggestion would be to throw away the mandrel and the busings. Buy yourself a good set of bushings and a dead center from http://www.penturnersproducts.com. Start turning between centers and you will never have an out of round problem again. JohnnyCNC's bushings have zero play in them and they are always perfectly centered. It's the only way I turn pens now.

Good Luck,
Dan

 

[randyrls]

I bought new bushings and these seem to fix my OOR cap problem (of course, could be I just got lucky again with the new ones).

One stupid mistake I made once was trying to use "B" size bushings on an "A" mandrel. :frown:

 

[Monty]

My suggestion would be to throw away the mandrel and the busings. Buy yourself a good set of bushings and a dead center from http://www.penturnersproducts.com. Start turning between centers and you will never have an out of round problem again. JohnnyCNC's bushings have zero play in them and they are always perfectly centered. It's the only way I turn pens now.

Good Luck,
Dan

I concur with Dan, I would even suggest turning the blank down to about 0.050 oversize, than remove the bushings altogether and replace the blank between centers using just the tubes. Turn the lath on and if there is any OOR, you'll be able to tell bu just touching the spinning blank.

 

[JimMc7]

My suggestion would be to throw away the mandrel and the busings. Buy yourself a good set of bushings and a dead center from http://www.penturnersproducts.com. Start turning between centers and you will never have an out of round problem again. JohnnyCNC's bushings have zero play in them and they are always perfectly centered. It's the only way I turn pens now.

Good Luck,
Dan

Thanks and sorry I wasn't clear on my last post but that's exactly what I did!

 

[RussFairfield]

Don't forget that the outa-round could be the result of differences in wood grain and sanding.

This is a common cause of the outa-round, and a lot of people spend a lot of time chasing their tail by looking at mandrels, bushings, and tail centers.

 

[Paul in OKC]

Don't forget that the outa-round could be the result of differences in wood grain and sanding.

This is a common cause of the outa-round, and a lot of people spend a lot of time chasing their tail by looking at mandrels, bushings, and tail centers.

I agree with you here, Russ. I wrote an article in the library about this topic (and what I think about the term OOR!). But I think as well two of the main things, one being wood grain. And the more I think about this, I have seen poor squareness of the pen milled end, and/or a bad angle on the pen mill. Some of the ones I have sharpened have had a concave shape from hand sharpening. Occasional touch up is good, but at some point they really need to be trued up again. Using a disc sander set up is different. How the bushings contact the end of the blank when all things are tightened up is critical. It will magnify any 'slop' there may be between bushings and mandrel. and, well.......

 

[leehljp]

I agree with you here, Russ. I wrote an article in the library about this topic (and what I think about the term OOR!).

Getting specific on terminology in a particular field that has beginners AND professionals can be as unobliging as helpful. While it is the ideal, the target audience and question must be considered.

Kinda like when I once told my wife I didn't like a curtain. She promtly told me in no uncertain terms that it was NOT a curtain, it was a "valance", IIRC.

Non-concentric and off-center descriptions to a question of "Why is the turned blank OOR?" will draw more "huh?" and What are you talking about . . often followed by a lengthy discussion that is Off Topic from the OP's question and intent. Concise explanations to the difference while focusing on the solutions to the problem is much more helpful and builds trust from the OP person.