STUCK BUSHINGS

[Drcal]

I have turned about a dozen Sierras in the past week and something unusual has happened. One bushing- the one closet to the headstock, has to be pried off when I am ready to assemble the pen. At first I thought it was the bushing itself so I tried a whole new set of bushings and the same thing happened. The pens assembled fine and work well.

When I am trying to get the bushing off, it spins freely in the tube but won't come out easily. It is as though it is in a groove or rut in the tube and it is always the bushing closest to the headstock.

Could it be a bad mandrel? I use a mandrel I have used for a long time---it is a MT#2 adjustable- the one that has the big locking collar on it.

Help!
Carmen
Tampa Bay

 

[johnnycnc]

Having seen this, I'll take an educated guess.
you are spinning/stalling the blank, usually happens while roughing.
The brass tube is being swaged by the spinning bushing.
It expands to the inside and fills the relief cut on the bushing.
It is then mechanically locked on, just as you describe.
Solution, don't stall the blank excessively. If/when it stalls, stop and retighten
your yummy mandrel setup to keep it from continuing.

 

[Mapster]

Check for burrs on the edge of the tube from squaring the blank. That is all I can think of.

 

[EBorraga]

Another suggestion is to contact Johnnycnc and get the bushings to TBC. Very reasonably priced and a great product. You'll never have to worry about bending mandrels again.

 

[Drcal]

Johnnycnc,you are a genius!!!

"Having seen this, I'll take an educated guess.
you are spinning/stalling the blank, usually happens while roughing.
The brass tube is being swaged by the spinning bushing.
It expands to the inside and fills the relief cut on the bushing.
It is then mechanically locked on, just as you describe.
Solution, don't stall the blank excessively. If/when it stalls, stop and retighten
your yummy mandrel setup to keep it from continuing."

That is exactly what has happened in all cases where I have had a stuck bushing. There were stalls. Thanks so much.

EBorraga- can you explain your post--Do you mean get the bushings TO TBC, as you said, or FROM TBC? And do you think it is a bent mandrel?
Also, I am not sure what TBC is?

Thanks, guys.
Carmen

 

[johnnycnc]

Good deal, Carmen! Glad I could help.
Been there ,done that a few times, and it sure is puzzling and frustrating until you figure out why..

 

[Craftdiggity]

EBorraga- can you explain your post--Do you mean get the bushings TO TBC, as you said, or FROM TBC? And do you think it is a bent mandrel?
Also, I am not sure what TBC is?

Thanks, guys.
Carmen

TBC = Turn Between Centers. This technique eliminates the use of the mandrel by using bushings designed to be mounted between centers.