Rounding square blanks?

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Woodchipper

Woodchipper

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Rounding prior to final turning? No problem with wood but synthetics, to use a generic term, is another matter. How do the members here do it? Jig of some kind?
 
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It's not pretty, but I usually put the square blank in a pen jaw chuck, with half of the blank sticking out - I then turn that half round, down to a diameter that will fit a collet. I then insert the part I just turned round into the collet, tighten it down, and then turn the remaining square half.
 
Turn between centers with a skew. I believe it is axminster tools from England that makes a set of centers which have a very small point and a cup.
Matched Pair - Cone Centers
1.Find rough center on both ends of the blank, using the corner to corner method.
2. mark that point with a spring center punch.
3. place between centers
4. turn to largest round diameter blank will allow creating a long cylinder as close to perfectly the same diameter throughout
5. remove centers
6. install collet chuck and collet to match diameter of the previously turned cylinder
7. drill for the tube side of your pen
8. Proceed with normal pen creation processes.
 
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Depending on the actual synthetic material, I will just turn it with negative rake tools or I will "round" the blank off on my belt sander to get things started.
 
I am from the school, it is a waste of time. I never found a need to round down a blank to make a pen. Carbide cutters has become my tool of choice to start all blank turning and I use the round cutter. Found no need for negative cutter. I did buy a few negative blades a few months ago but have not tried them because no shop time till winter months again. But after carbide gets me close, I always break out the trusty skew to finish all blanks up. It a matter of choice I guess. It comes down to learning technique when using turning tools I guess.
 
KMCloonan said:
It's not pretty, but I usually put the square blank in a pen jaw chuck, with half of the blank sticking out - I then turn that half round, down to a diameter that will fit a collet. I then insert the part I just turned round into the collet, tighten it down, and then turn the remaining square half.
Click to expand...

+1 for this method if I really need it to start my process with a round blank.
 
Woodchipper said:
Rounding prior to final turning? No problem with wood but synthetics, to use a generic term, is another matter. How do the members here do it? Jig of some kind?
Click to expand...
Just the same as wood, put it on the mandrel but using carbide tools to take it down to size I want, then scrapers to finish. Not something that I turn often, it's so messy and time consuming that I don't enjoy it.
 
sisbra, don't have carbide tools...yet but considering it. Yes, messy; figured one blank took a half hour to turn to dimensions. John T. has some good info, too.
 
A variant of Kevin's process... Jam one end into my Er32 chuck without nut/collet. Other end live center in tailstock. Turn the tailstock half to 3/4 inch round. Flip the blank & mount into headstock er32 using collet & nut. Turn other square end round to 3/4 inch. I use an open end 3/4" wrench to gauge diameter.
 
I treat them the same as wood. Drill it and glue in the brass tubes while it's square. Flush up ends. Turn between centers or on mandrel. With wood I usually use a spindle roughing gouge to knock of corners and a skew to shape. With synthetics I just use my radiused square carbide tool. Even with chippy stuff like polyester, my normal carbide cutting bit can be presented pointing down as a "negative rake" tool to give a good surface finish. Generally I start sanding synthetics at 320 or so.
 
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