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.
 
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.
 
For Acrylic I round the corners using my 6" belt sander. I also do the same for hardwoods and woods that may have "hard" spots in them, like Koa. Doesn't take much time and it sure helps.
 
As you can see from the varied responses many round their blanks on the lathe as part of the turning process. Others use sanders and other jigs to cut the corners off before they start turning.

Personally, I have never liked the little "impact" forces that an out-of-round blank puts on my cutters so I almost always cut the sharp corners off of my blanks before I put them on the lathe. I started out using my belt sander to get them kind of round, but a few years ago I started using a jig that I came up with that works along with my bandsaw fence. It is based on one that PSI used to sell called the Corner-B-Gone Pen blank Preparing Jig. I made mine out of wood instead of aluminum though. I used a 1/4-20 threaded rod for the mandrel. A 3D printed version would have been much easier to make, but I just haven't made the leap into 3D printing - yet that is.

Since my jig cuts in reference to the center line of the tubes and bushings instead of just one side of the blank, it even helps compensate when the blanks are not drilled straight through from end to end or when the blanks are rectangular rather than square or if they have an irregular shape such as a piece of FOG wood or a deer antler. (I also use it sometimes to remove some of the bulk of the blank if I have one that is considerably larger than the pen I am making). - Dave

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I drill and tube my blank then turn between centers using some sort of gouge to round it up. Roughing Gouge, Spindle Gouge or Bowl Gouge all work but mostly the roughing gouge. Once the blank is round I reach for a skew.
Yes, resin blanks take longer to turn than wood.
I do not own a collet system and probably never will.
 
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