Problem with my mandrel....I think.

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jmiket91

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So I turned my first pen after Christmas - turned around 25 or so total during the season - and I got terrible results. I pressed all of the parts in correctly, yet when put together, the pen is bend around the center band. I did notice that the mandrel seemed to be turning the exact same way on the lathe. The bushings did not even seem round when spinning. Generally I wouldn't be concerned, I'd chalk it up to just needing a new mandrel, but this mandrel has only been used to turn five or six pens. Maybe my lathe isn't turning true? Maybe it's time to go mandrel-less? Anyway, please help. I've included a picture.

 
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DCBluesman

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Looks like the lower barrel was not properly squared. In your photo, notice the difference in the gap between the wood and the center band where the lower barrel meets. The top seems much wider than the bottom.
 

Lenny

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Have you checked the alignment between headstock and tailstock by placing centers in each and bringing them together to see if the points line up.
Perhaps you do have a bad mandrel.
Check out Russ Fairfield site for lots of good information about this problem and other stuff!!
http://www.woodturnerruss.com/Pen12b.html
 

leehljp

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Mike,

Are you using the stock live center that came with the lathe? If so, that could be your problem. If the lathe is not turning true in making a pen, - a large portion of these problems occur from using the wrong live center in the tail stock. You need a 60° live center for the mandrel. If you have a 60° LC, then the next thing to check out is the mandrel, followed by dirt in the Morse Taper. And as mentioned by Lenny, check the alignment of the tail stock to the head stock. Too tight on the tail stock against the mandrel will also cause similar.

These are the most common for new turners and are easy to check and fix. Get a 60° LC; Straighten or get new Mandrel; clean the Taper; pull the tail stock to the head stock with centers in both. Do they align with each other?

As Lou said, the bend could be from the ends not being square.


AND about Mandrel-less or TBC, it does eliminate many problems that occur early on for many beginners.
 
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jttheclockman

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Check further down in this forum and someone else is have crooked pen problems and a list was given for the many things that can go wrong. To tell you exactly would be inpossible. You need to check all these things yourself. We would only be guessing. Good luck.
 

jmiket91

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Thanks guys.

I actually just went and checked - it was both of my mandrels. I suppose I'm tightening the mandrel into the headstock way to tightly with the live center....

Is there a tutorial on how to turn between centers? Is all I'll really need the dead center? I've got several pens that I need to turn ASAP.
 

WildcatHollow

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Another Thought...

Roll your mandrels on a flat surface. That will tell you if they're out of round or not.

If they're not out of round, is there a chance that you're pushing the tailstock and live center too much into the mandrel? That would cause the mandrel to bend at the center bushing, which would cause the curvature that you see in your pens.

Regards,

t.
 

johnnycnc

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Thanks guys.

I actually just went and checked - it was both of my mandrels. I suppose I'm tightening the mandrel into the headstock way to tightly with the live center....

Is there a tutorial on how to turn between centers? Is all I'll really need the dead center? I've got several pens that I need to turn ASAP.

One of our members here did a tutorial recently on this..
http://www.penturners.org/forum/showthread.php?t=54760

I am starting my own series on such things, I have a video # 1 up on youtube
as a trial, it is only about centers. I am a rank amateur at video, so it is what it is.. I will have another attempt soon.:) The tail end got clipped, youtubes 10 minute limit bit me.
http://www.youtube.com/watch?v=_c--nfxh8og

And jumping into a new technique with a bunch of pens to turn asap, as you say, may not be the best idea. Like many things, first you get good, then you get fast.:yin-yang:
 

jmiket91

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And jumping into a new technique with a bunch of pens to turn asap, as you say, may not be the best idea. Like many things, first you get good, then you get fast.:yin-yang:

Great point you have. I'm going to turn these few on a new mandrel and take extra care not to tighten it too hard with the live center, and when I'm working on my own time, I'm going to learn to turn between centers. I read the tutorial you linked me, and I watched the video. Both were great! Pretty soon I'm going to buy the TBC starter kit from your website. Thanks!
 

johnnycnc

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Great point you have. I'm going to turn these few on a new mandrel and take extra care not to tighten it too hard with the live center, and when I'm working on my own time, I'm going to learn to turn between centers. I read the tutorial you linked me, and I watched the video. Both were great! Pretty soon I'm going to buy the TBC starter kit from your website. Thanks!

I think we can turn decent pens on a mandrel, it just takes some investigating to find the problem when things go wrong.
In my humble opinion, between centers has a lot more trouble-free things to offer, and better results to boot.
I'm glad you enjoyed the links!
If I can be of help with any pointers, email me.:)
 

JakeAB

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I am starting my own series on such things, I have a video # 1 up on youtube
as a trial, it is only about centers. I am a rank amateur at video, so it is what it is.. I will have another attempt soon.

Hey John,

You may be a rank amateur at video, but your video #1 sure turned out great. I learned more in ten minutes than I usually do in a couple hours of web surfing. I hope this is the first in a long series.

I wouldn't worry about the end of the video being cut off by YouTube. Just call it a cliff-hanger and pretend you did it on purpose. Now if you just add some laser beams and explosions, you'll really catch our attention!:biggrin:
 

jleiwig

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John thanks for the video, I look forward to more. My wife was wondering what a Southerner was doing in Indiana?!

Hasen't been to Indiana much has she?

I dated a pretty little thing from Rockport, Indiana (Across the river from Owensboro,KY), and you would have thought she had stepped right off of a Georgia plantation. I always imagined her daddy as Rhett Butler for some reason due to the way he talked. :biggrin:

Thanks for bringing back some good memories of days gone by Rob!

Now back to the original post, I'd be inclined to agree with Lou. You didn't get the ends of the blank perfectly square. Even a bit of finish run over to make a ridge will knock your pen off kilter like that.
 
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And jumping into a new technique with a bunch of pens to turn asap, as you say, may not be the best idea. Like many things, first you get good, then you get fast.:yin-yang:

Actually, not to dispute what Johnny said, but if you try the between centers once, using a good dead center and the proper bushings, you'll find it actually easier than using the mandrel... I bought Johnny's dead center and the 7mm slimline bushings from him and the first pen I tried, I wondered why I had not switched sooner. If you're good on a mandrel, you'll be better on TBC.

I would do a test run on a couple before I jumped into an order, just to get the feel of working that close...
 

johnnycnc

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Actually, not to dispute what Johnny said, but if you try the between centers once, using a good dead center and the proper bushings, you'll find it actually easier than using the mandrel... I bought Johnny's dead center and the 7mm slimline bushings from him and the first pen I tried, I wondered why I had not switched sooner. If you're good on a mandrel, you'll be better on TBC.

I would do a test run on a couple before I jumped into an order, just to get the feel of working that close...

Chuck, I can't argue with you.
I go overboard not to come across as self-serving..that's just not what I am here for.:biggrin:
Between centers is the only way to go in my book,
and is so darn easy for me, surely anyone can do it!
 
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johnnycnc Bushings

Hi John,

I finally got to try the bushings, the Cambridge set. Excellent my friend. Thanks.
BTW, I watched your video. Also excellent. I never knew you could lub the bearings in that live center. I had parked my copy of that center because it seemed a little sluggish, like it was lubed with heavy grease. Actually had to tighten the quill tighter than comfortable when finishing without bushings so I switched to a OneWay. I'm going to get the other one out and try the lub. Thanks again.
 

GouletPens

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What method are you using to square the ends of your blanks before turning? If you're not squaring them, that would certainly throw your mandrel out of whack, even with the lightest pressure. If you have an out of round turning, it'll cause one side of the pen to be below the level of the hardware, and the other side to be above the level of hardware. I don't think that's' necessarily what you're faced with here. It looks more like a squaring problem to me, especially since the pen is cocked like that. Investigate further into that, because you're just pissing up a flagpole with the mandrel thing if your blanks aren't square on the ends.
 
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