"Zero" or "Hero" as the say on Shark Tank

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TonyL

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Mar 9, 2014
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Some of TBC (with TBC bushings as opposed to directly on centers and use calipers). Now, I understand there may be a run-out issue, but what about a SS, double-sided conical "nipple", insert, coupler, etc. that fits in between the upper barrel pair of TBC bushings of the lower barrel pair of TBC bushings? Assuming run-out is not an issue as we move further from the HS, wouldn't that be a way of enjoying the double-barrel turning of a mandrel with the accuracy of TBC bushings? I am really asking you expert, engineering, mathematical and just plain ol' smarter than me types :). What do you think?

This insert would be no more than two 60 degree comes with their bases touching each other (of course, all one piece.).



Thanks for reading (and very likely laughing) :)

PS. Not looking to be laughed off of Shark Tank, just for a way for this lazy pen turner to get more done in less time without comprising quality. I make my HDPE CA bushing that way; why not SS?
 
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BeeAMaker

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Not laughing a all, I wonder how that would work my self. In fact, I searched for something like this briefly when I ditched the mandrel and went to TBC. I mostly do single tube pens so I didn't look real hard, and didn't think much of it when not finding anything.
 

BeeAMaker

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How is turning on a mandrel any less accurate than between centers? It's only less accurate if you let it be.

The issues I have had is the mandrel not straight causing chatter on the outer blank. Or bowing in the middle. Even with a mandrel saver.

I also had one issue when the bushing got some grit under it and welded itself to the mandrel - almost lost the blank.
 

dogcatcher

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Why not just make TBC bushings out of HDPE? I made mine out of aluminum, and instead of "powering" it with a dead center I made the one for the headstock 1/2" round and I use it in my collet chuck.
 

Dale Allen

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Akron, OH
Tony, I'm no expert but here is my humble opinion.
BTW, I may try this after the holidays.
The use of TBC bushings reduces to '1' the number of points that can contribute to off center conditions.
There is no fit issue between the 60 degree center and the bushing because it is a pressure fit. The only place there can be a 'wobble' that could cause an out of center condition is where the bushing fits inside the tube.
When I make TBC bushings they are usually so tight fitting that I have difficulty removing them from the tube. In this way I am assured thy are not 'wobbling' inside the tube. There is still some 'play' in the fit but very little. The bushings cannot be made with absolutely no play because they would not fit inside the tube. I make my own to fit the tube I'm working with because I've seen the tubes vary somewhat from kit to kit from the same vendor. It stands to reason that the manufacturer of the brass tubes, which is likely not the kit manufacturer, does not hold tolerances to a high degree.
If I were to do this I would make a joining bushing that would fit tight into the ends and be at least 1" long inside the tube. That 'may' prevent the assemble from bowing when between the centers, but I'm not sure it would do well under the pressure of the lathe tools during turning.

Putting an additional fitting between the TBC bushing would just add another flex point and would be counter-productive, IMHO.
 

More4dan

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Katy, TX
I’ve tried something similar for jambs for larger diameter pepper mills. It was difficult to get all the pieces to fully align. It exaggerated the error than you would see for smaller pen IDs but I’m guessing it could still be an issue. For blanks that I have to turn close to the brass, I sometime nick my centers. One option is make your dead center out of simple steel that can be redressed with a file. Turn the end finished to the dead center then flip around and turn the other end. Protects the live center




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dogcatcher

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I’ve tried something similar for jambs for larger diameter pepper mills. It was difficult to get all the pieces to fully align. It exaggerated the error than you would see for smaller pen IDs but I’m guessing it could still be an issue. For blanks that I have to turn close to the brass, I sometime nick my centers. One option is make your dead center out of simple steel that can be redressed with a file. Turn the end finished to the dead center then flip around and turn the other end. Protects the live center

Sent from my iPhone using Penturners.org mobile app

For items like pepper mills, I use a blank that I turn in one piece so I have enough to shove in both ends of the pepper mill blank. In the pics is a duck call blank. The headstock is drilled and tapped to screw onto the headstock. The tailstock end is drilled for a 60 degree live center. The blank is turned as one piece and cut in two piece, runs as true as your lathe is.

I have use this method to turn all kinds of things, including pens, duck calls, flutes, pepper mills and a yarn "doohickey" for my wife.
 

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sbwertz

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May 11, 2010
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Phoenix, AZ
I’ve tried something similar for jambs for larger diameter pepper mills. It was difficult to get all the pieces to fully align. It exaggerated the error than you would see for smaller pen IDs but I’m guessing it could still be an issue. For blanks that I have to turn close to the brass, I sometime nick my centers. One option is make your dead center out of simple steel that can be redressed with a file. Turn the end finished to the dead center then flip around and turn the other end. Protects the live center

Sent from my iPhone using Penturners.org mobile app

For items like pepper mills, I use a blank that I turn in one piece so I have enough to shove in both ends of the pepper mill blank. In the pics is a duck call blank. The headstock is drilled and tapped to screw onto the headstock. The tailstock end is drilled for a 60 degree live center. The blank is turned as one piece and cut in two piece, runs as true as your lathe is.

I have use this method to turn all kinds of things, including pens, duck calls, flutes, pepper mills and a yarn "doohickey" for my wife.

For peppermills, I turned a mandrel from hardwood with a #2 MT for the headstock and a 1" tenon that fits the peppermill blanks for the PSI antique style peppermills. For the tailstock I use a large (1 11/16") 60 degree live center directly in the 1" hole in the blank. This makes it self centering. These are the only peppermills we turn at the Center for the Blind because they are basically just a VERY large pen blank! My blind turners can make them with ease. The mill just screws on the top.
 
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