PLEASE HELP

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weaveand

Member
Joined
Feb 2, 2017
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15
Location
Pennsylvania
Looking for any help I can get. I have been turning pens for a while. Recently I have been gettino pens that are not perfectly round. The are flush with the bushings in one spot, but raised just a hair about the bushing in another spot. I use a 60 degree tailstock. I do not over tighten or put to much pressure on it with the tailstock. I thought maybe my issue was the mandrel so I went out anduring bought a brand new one from woodcraft and I am still having the same problem. My headstock and tailstock are lined up perfectly. What is causing this issue?
 
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How tight do your bushings fit? I never realized how much slop there is in many bushings 'til I switched to precision TBC bushings--they fit TIGHT. Oh, and you might consider scrapping the mandrel and turning between centers, which will eliminate any chance of the mandrel bending.
 
TBC Bushings?

So, where does one find TBC Bushings?

mecompco said:
How tight do your bushings fit? I never realized how much slop there is in many bushings 'til I switched to precision TBC bushings--they fit TIGHT. Oh, and you might consider scrapping the mandrel and turning between centers, which will eliminate any chance of the mandrel bending.
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weaveand said:
My headstock and tailstock are lined up perfectly.
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What is your definition of "perfectly"? Have you checked alignment with tailstock quill fully extended as well as retracted?

Have you measured the run-out at both ends of the mandrel (with and without the tailstock supporting the tail end)? This can reveal if the mandrel is not on axis (which would mean when you bring up the tailstock it's deforming the mandrel slightly).
 
Take the blank off and watch just the mandrel spin. If it is dead on, the problem is your bushings, if it is NOT dead on, the mandrel or drive is the problem.

Once you isolate the problem (buying a new mandrel should eliminate the mandrel, but it could still be off center due to crud in the morse taper--headstock), fixing it is much easier.
 
weaveand said:
What do you mean by measuring the run-out?
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Checking to see how much wobble there is in your work at "x" distance from the spindle.


One of the easier ways to check for run-out is to take a known good shaft and mount it in your chuck, and looking for wobble along it's length as it spins.


Make certain that your morse taper is clean inside, as anything stuck in there will affect how much run-out will be apparent, because the tool accessory is not seated properly.
 
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