Turning Burl (Trying That is)

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Rags

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Winchester, Ca, USA.
Well I successfully turned one pen from coolibah burl but have now had two failures in a row. I guess I was just lucky on the first one. I have been keeping the tools sharp (4-5 sharpening per session) and going slow attempting to take shallow cuts on each pass. I am using a gouge (small one) and as I get down to about 1/8" thickness left I am getting "catches" and eventually the wood has split both times. Always happens at the bushing.

So I am looking for advice/guidance on what I may be doing wrong. I am running the lathe at 3000rpm which seemed to work very well on non-burl woods like cocobola, goncalo alves, curly maple and a few others. Maybe this is the problem (too fast) but I don't want to take a chance on ruining another blank. The blanks do seem to be very dry and hard as they were difficult to drill using a new bit. In fact the blanks were smoking when I drilled them even when lowering the bit slowly. DP speed was 1950 rpm.

Any advice would be greatly appreciated. It may just be my lack of experience or current skill level but thought I would seek the wisdom on the forum. Thanks in advance.
 
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Bill,
I used to have the same problem until I started using a skew, My blow-outs dropped off, then I started doing what shane said and stabilizing with thin CA. I lay wax paper under by blank and across the lathe and hand turn the blank while drenching with thin CA. after I turn thru the CA I stop and add some more, turn, add, until I get the shape and size I want. Now very seldom do I have a blow-out. I also do the same with segmented blanks.

Rob
 
what Rob said...the skew is the best tool for problem woods (and all others and acrylics) but it must be sharp and use very light shearing cuts (look in the libary for tips on the proper use of the skew) and the thin ca will harden the wood and and bind it together which will help prevent blow outs
 
I started to have the same problem with Jarra burl. I was just starting to come apart. Luckily I noticed that is was and then I soaked it with CA a couple of times and . Ended up fill some voids with CA and the pen turned out really cool.
 
I use a roughing gouge but I use just the end of it, may as well get a good quality skew and be done with it.

IF the wood is soft, bad or what not then take it to a belt sander first, get the basic roundish shape then use the chisels on it to smooth it up.

Ed
 
Rags,
What works for me is
1. making sure the glue to the brass tube is good. Brass tube must be sanded to get tooth. Hole correct sized, not to big. Glue aa the tube without pockets.
2. Gouges may work for initail cuts, but a skew is what works best. SHARP skew cutting as a skew, than used a scraper to get the final exact sizes at the end.
3. LIGHT CUTS, especailly near the end.
Rich S.
 
Skew is the best tool for the job.

Also, make sure your cuts go from the middle of the barrel to the bushings. Coming from the bushings inward increases the chance of catches significantly.

Dave
 
you might want to check how tight you're tightening the nut on the end of the mandrel. i've had a few crack/chip out when i tightened it too much. it really doesn't take much pressure at all.
 
If it is always happening at the bushings, make sure that you are milling the wood dead even with the end of the brass tube.

As far as sanding the brass tubes goes, I know a lot of people do that, but I quit doing it several months ago and have had only one failure since then. The single failure occurred where there was absolutely no glue on the tube.
 
Welcome to the forum. As everyone says high speeds work best. However if you dont have sharp tools and take light cuts your chances of a blowout are higher at high speeds from my experience. The blank is much more forgiving when you stabalize with thin CA.
 
High speed! Gouge is fine for rounding, but I use a round nosed scrapper. For final shaping, a skew is the way to go. Or, on some very notty woods, sand baby sand!
 
Some of my experiences,
First off the speed on your drill press is excessive and causes excessive heating the magic speed is about 900 rpm for me
What type of glue do you use to glue up the blanks? I use epoxy and then heat cure it
I use a round nose scraper, just my preference skew works too,
if it is still a problem i turn pretty large and then just use 60 grit to take it down to the bushings.
 
Disagree with the slow advice. Fast reduces chances of catches and blow-outs and gives smoother cuts. But, for burls, stabilizing is really highly reccomended. Just consider the grain pattern, or rather lack of it, with burls. They are just looking for an excuse to come apart. I have a stack on my bench now that will be sent off for stable process. BTW, stable adds beauty to the wood.
 
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