TBC Two Barrel At A Time

[TonyL]

I would think that some one has thought of this well before I did.

If it is possible as the best of mandrel-less turning:

TBC with and double-sided bushing/insert in between the upper and lower barrel.

So from left to right:

Drive center, bushing, upper barrel, bushing with double-sided insert, lower barrel, bushing, live center.

Is there such a thing, will the length of this cause run-off, is this the dumbest thing you ever heard? Be blunt

 

[kingkeyman]

I would think it would cause more runout than a mandrel, seeing as how there is no active support for the center bushing.

 

[skiprat]

I made these sets of mandrel/bushes some time back. The tolerances are pretty good and the sections that go inside the tubes virtually fill the entire length of tube, so they have plenty of support.
These are particulary good if you don't have a very short tool rest, to do one barrel at a time. Also great for closed ended pens:wink:

 

[TonyL]

Nicely done.

So I guess the answer is don't try it.

 

[BigShed]

I would think it would cause more runout than a mandrel, seeing as how there is no active support for the center bushing.

Yes that has been my experience.

 

[JTisher]

I thought about making a set, then I stopped using bushing altogether. Now I measure the individual pieces and turn the barrels to suit.

Joe

 

[Smitty37]

You know I think I'll try it. I have some larger bushings that are designed to go into both tubes in the center and TBC bushings for the ends. I'll just use a blank that's not worth much and see how it ends up. I think with a fairly light touch it will be OK.

On the other hand, even if it works fine, I don't see much reason to do it. It won't make much difference in time.

 

[ed4copies]

Smitty, your hypothesis includes turning carefully (one might imply "take off less material each pass"). So, the overall time will be longer.

I understand those who say they want "production", so they use TBC to save seconds between pens---however, using 2 tubes would have NO advantages, that I can see--am I missing something??

Thanks,
Ed

 

[TonyL]

If i can find a double-sided insert bushing, I will try it with some AA shorts.

 

[Smitty37]

Smitty, your hypothesis includes turning carefully (one might imply "take off less material each pass"). So, the overall time will be longer.

I understand those who say they want "production", so they use TBC to save seconds between pens---however, using 2 tubes would have NO advantages, that I can see--am I missing something??

Thanks,
Ed

I agree fully. If you notice my last sentence Ed, I don't see any real reason to do it...I just might try it to see if it comes out OK, Even if it works I won't adopt it.

I have to take pretty light cuts anyway (age and eyesight) and I am never in a big hurry to get a pen finished so more or less a few seconds or even minutes means nothing to me.

 

[skiprat]

Aah, the pen gods have spoken! LOL....
Just because some old dog can't ( or won't ) see any merit in learning a new trick, doesn't mean that there isn't any advantages to trying something new. I can think of several good advantages.
Just because some people can't see them, doesn't mean they are not there.

 

[robersonjr]

I strongly suggest you not try using just a two sided bushing for the center, the pressure of the chisel will force the blanks to bow out and become a serious danger to yourself. If you cannot support the entire length then stick to a regular mandrel. Just my two cents. Robbie

 

[Smitty37]

Aah, the pen gods have spoken! LOL....
Just because some old dog can't ( or won't ) see any merit in learning a new trick, doesn't mean that there isn't any advantages to trying something new. I can think of several good advantages.
Just because some people can't see them, doesn't mean they are not there.

Pen Gods? Plural? Who's the other one?:biggrin:

 

[Smitty37]

I strongly suggest you not try using just a two sided bushing for the center, the pressure of the chisel will force the blanks to bow out and become a serious danger to yourself. If you cannot support the entire length then stick to a regular mandrel. Just my two cents. Robbie

I think that with a typical mandrel style center bushing (for pens with larger than 7mm barrels, the part of the bushing inserted into the barrel and the longitufnal pressure provided from the centers there will be more than enough strength to prevent what you fear. I'll find out when I go back to my lathe. Generally speaking I would have far more concern of "bowing" when sanding or finishing than when cutting...I put considerable horizontal pressure on the barrels to generate heat when finishing (because a lot of finishes need heat to activate properly) and very little horizontal pressure when cutting - I am after all using a chisel - not a jack-hammer.

 

[TonyL]

I strongly suggest you not try using just a two sided bushing for the center, the pressure of the chisel will force the blanks to bow out and become a serious danger to yourself. If you cannot support the entire length then stick to a regular mandrel. Just my two cents. Robbie

Never thought of that. Thank you