Wierd cause for a 'wobble'

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MobilMan

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Mar 30, 2008
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Started turning a Wall Street11 with corn cob & noticed the right hand bushing jumping around. Very visible amount. Cob out of balance, so kept turning til it was round & somewhat smaller. Still got a dancing bushing. Something wrong here. I had just turned a Wall Street11 Click & it was running perfect. LOML latched on to that one as soon as it was assembled. "That's Mine. It's not going in the pen case". Anyway, wassa matter here? I had the slimline bushing-the WS bushing-the blank-the WS bushing then a turned blank as a spacer then nut. I had used two small homemade slimline bushings on the last setup for spacers. So I reset the setup same as before. Back to the lathe. Runs perfect again. I can normally move the tailstock away from the mandrel & the runout is hard to see. Almost perfect. I always put the mandrel in the headstock kinda loose then slide the tail forward into the end of the mandrel with a easy push then lock the tail end & finish setting the mandrel with the crank. I don't tighten the knurled nut, just snug. That way instead of a catch, it stops the blank. Just lighten up on the pressure of the gouge. Beats the heck outta me. The blank spacer is same as ready to make a pen, been milled & polished. The reason I posted this here is there a lot of 'wobble' questions here & maybe changing the setup will help in some cases. Anyone else ever had this happen?
 
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I found that some non-adjustable mandrels have a shallow tapered cone where the tail stock bit holds the end, and I've seen (and experienced) the wobble you describe. I recently purchased an adjustable mandrel from Woodcraft and the end taper is deeper allowing the tail stock spindle tapered bit to better hold the mandrel end. I have no wobble problems with this spindle.
 

thewishman

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My advisors firmly instructed me to firmly seat the morse taper firmly in the headstock before doing anything else with it. Yes, that sentence is correct and intentional.
 

leehljp

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Are you using a 60° live center? If not, you should be.

In another vein, with all the problems that can cause wobble, the majority are related to mandrels in one way or another. Eliminate that and most wobbles will be gone.
 

papaturner

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Buchanan,Georgia USA
The only strange wobble I`ve ever gotten was when I didn`t get the bushing off the threads of the mandrel. Did not adjust the length of the mandrel long enough,thatfore the last bushing did not go pass the threads. That will cause wobble and a pen that is out of round. Don`t you just love experience.:rolleyes:
 

MobilMan

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Hank. I had been using the 60deg for something else a few months ago & just left it on there. What I was talking about wasn't live center or crooked mandrel. It runs perfectly straight without the tail stock in place. What caused the wobble was the different spacer I used when it wobbled. Went back to the little spacers & it quit. Couldn't figure why a longer spacer caused it. Turned another WS11 today with same setup & like always--straight & true.
Vince. I hear that. I got rid of the wobble problem a couple of years ago when I noticed the point on the live center was bottoming out. Drilled it out deeper & took care of it. I can use a 60 deg. or the origional live center without a problem.
 

leehljp

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Hank. I had been using the 60deg for something else a few months ago & just left it on there. What I was talking about wasn't live center or crooked mandrel. It runs perfectly straight without the tail stock in place. What caused the wobble was the different spacer I used when it wobbled. Went back to the little spacers & it quit. Couldn't figure why a longer spacer caused it. Turned another WS11 today with same setup & like always--straight & true.

OK, One other thing that I ran into once: If the blank/tube is not square OR the spacer is not square, or too large, or has a burr or nick on it - then as it is tightened, it can force the blank to cant just enough to cause some wobble. Not sure if this is the problem, but worth checking out.
 
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Are you using a 60° live center? If not, you should be.

In another vein, with all the problems that can cause wobble, the majority are related to mandrels in one way or another. Eliminate that and most wobbles will be gone.

Hank,
I do believe your are a firm, repeat firm, advocate of the no mandrel method... mandrel manufacturers will have a contract on you soon.
 

MobilMan

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Hank/Bruce. That's what's got me puzzled. The longer spacer is a 7mm tubed & polished blank that was going to be the longer half of an European kit. But as luck would have it, the upper half was wasted, [guess how] so this has been in the drawer for a couple of years. Beats heck outta me. Once before I had turned a set of blanks, but just slowed the lathe speed down to sand. Got a small but noticable vibration/wobble, so increased the speed & it went away. But I guess that's part of the fun in turning, figuring out these little quirks.
 
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