Trouble turning Burl

[mpex]

I'm having trouble turning a couple Burls. The two that I have tried are Red wood and Coolibah. At least 50% of them crack while turning. When I say crack, I mean a big or small chunk flies off. I had an amazing Coolibah on the lathe yesterday, had turned down the bottom piece and prepped for finish, had almost completely finished the top and was just going back over with a skew and a chunk came flying off.

So my question is, is there anything I can do to help prevent this from happening?

Method: Turn blanks around 1900-2000 rpm with a rougher. Sometimes I start out a bit slower. I try not to turn aggressively, trimming off a small amount of wood with each pass. Once I have the shape right, I use a skew to smooth out any small gouges and to refine the shape and put the right circumference on the ends.

Is it also possible that my tools are not sharp enough? I had them professionally sharpened about 20 pens ago (mix of hard/soft woods.)

Thanks!

 

[nava1uni]

I think that part of the problem is that your tools are not sharp. I sharpen my tools constantly while turning. Either with a grinder and then a diamond hone in between using the grinder. Burls have lots of voids that can catch and often the wood is soft. You can use thin CA to stabilize it before you start and then while you are turning so that you can turn it better.

 

[Steve Busey]

How dry are the blanks? If they're still "green" or wet, they're very prone to move/crack as they get thinner. When dealing with burls, if you can get stabilized blanks, you'd likely get better results.

 

[George Watkins]

Is it also possible that my tools are not sharp enough? I had them professionally sharpened about 20 pens ago (mix of hard/soft woods.)

Thanks!

I think this is your problem- I sharpen my tools before every pen I turn and then quite often before I take the final cut as well.
also allot of burl wood can blunt tools faster than most normal woods, this seems more so with some of the ozzy burls like coolibah, jarrah, salmon gum etc

you also don't mention what glue your using? you can get failures in all materials if you don't get an even spread of glue over the whole tube.

 

[ed4copies]

As you turn the burl, if you are seeing a lot of endgrain, add some thin CA. This will seep into the wood and reinforce it.

"Professionally sharpened" tools are great, but you really need to watch and learn to sharpen your own tools, OFTEN. Turning requires sharp tools!! IF you just can't figure out how to sharpen, then use carbide insert tools.
(Not meant as a "slam", sharpening is a MUST for good turning!!)

 

[Sawdust46]

I'm right on with ed4copies. If I have a soft or "sensitive" wood that appears like it might catch or if the is a small knot that might loosen, I coat it with thin CA. Just be carefull you don't glue the tube to the bushing!
I also have learned the hard way to keep my tools sharp. I would recommend you get some kind of sharping system. You will get to where you can sharpen a tool in 2 or 3 minutes.

 

[CharlesJohnson]

If you use flat surface carbid inserts,they are Real easy. Flat top surface down on a diamond card. These cards are not expencive either.

 

[woodbutcher]

Is it also possible that my tools are not sharp enough? I had them professionally sharpened about 20 pens ago (mix of hard/soft woods.)

Thanks!

I think this is your problem- I sharpen my tools before every pen I turn and then quite often before I take the final cut as well.
also allot of burl wood can blunt tools faster than most normal woods, this seems more so with some of the ozzy burls like coolibah, jarrah, salmon gum etc

you also don't mention what glue your using? you can get failures in all materials if you don't get an even spread of glue over the whole tube.

As you turn the burl, if you are seeing a lot of endgrain, add some thin CA. This will seep into the wood and reinforce it.

"Professionally sharpened" tools are great, but you really need to watch and learn to sharpen your own tools, OFTEN. Turning requires sharp tools!! IF you just can't figure out how to sharpen, then use carbide insert tools.
(Not meant as a "slam", sharpening is a MUST for good turning!!)

You can learn a lot listening to these guys.

 

[low_48]

Are you using the skew like a scraper, or with fine shearing cuts? Shearing cuts are the best of course. What glue are you using? If you are using CA, you may not be getting a 100% bond between the brass and the wood. I prefer epoxy.

 

[switch62]

+1 on all posts above.
If your burl has a lot of voids and very "burly" then as you turn off the outer layers you are actually removing support for some parts of the burl. Hence peices flying out. If you get stabilised burl (all the voids filled with plastic) or soak the barrels with thin CA as you go, these pieces will stay glued in. You can also fiil voids with sanding dust and thin CA.

TonyO

 

[PenPal]

Just a thought from me try using a gouge all the way sharp if experience is haunting you a Skew surely will, life around here is made up of burl burl burl, look for the t_________ighter burl and be careful where you buy. I work with tough stuff especially for pen rests all burl caps near the outside where the bark was.

Have a mate who uses up to 16 timbers including many burls in any one bud vase finishing the surface with 26 coats of french polish where any or every blemish will show they sell for 800 dollars plus. Turning is not his profession rather furniture making.

Recently I changed computers and to recover pics is proving difficult but if you go to my past posts you can see some of the burl I work with for pen rests etc.

As in the Olympics every timber has its degree of difficulty mastering the easy burls such as Amboyna and your typical American timbers can lead the way to experience a blunt tool can never be anything but a recipe for problems.

A mate of mine sharpened his gouges using a plain rest holding the chisel at a flat face across the grinding disk looking down so his grind was flatish not hollowed all his long turning life, another used bridge timber up to 80 pounds with only a flat scraper winning more first prizes than most commencing turning in his older age. His tool skills were average but the finished huge pieces beautiful.

The suggestions for you from others are valid, ie harden the surface , sharp chisels that cut there is a difference here. Have success but stay with easier spectacular timbers remember to trust suppliers only when you deal with the ones on this forum or recommended dont be afraid to pay for quality timber blanks, seek help in person where you live.

Have fun Kind regards Peter.

 

[PenPal]

Some examples reference previous posts

Amboyna Burl Rosewood 11.9.12
Reverse swap for Hans 2 entries 8.9.12
Gift for a mate 5.16.12
Pith swap to Don Ward from me 2.28.12
My sister turns8 Tee 11.15.12
Amboyna Burl 11.9.11

Kind regards Peter.

 

[mpex]

Well, I got a Woodchuck Pro in the mail yesterday and gave it a try. No problems! The other 2 things I did was not to use a skew at the end. I was able to get it to ready to sand with the Woodchuck. I also left the blanks 1mm thick and did the rest with sand paper. I filled the voids before I started sanding. Still a bit early to jump up and down, but
it all worked! Will do final finishing tonight.
Thanks so much for the advice!

 

[Sawdust46]

You've gotten some excellent feedback and it sounds like you are getting results. You're on your way to addiction!

 

[Hubert H]

Just wondering? Could it be that the Coolibah burl blank was just one of those XXXX. I had a Coolibah blank that was a bear. I sharpened my tools 4 or 5 times - maybe 6. I used CA to reinforce the end grain. I finally had a nice pen. I have never had another Coolibah blank act like that one.

 

[dbarrash]

Sharpen before each pen..............Sharpen during each pen..........
I have so for to go! Every time I come to this forum I learn so much!
Thanks all!

Dave

 

[mpex]

Just wondering? Could it be that the Coolibah burl blank was just one of those XXXX. I had a Coolibah blank that was a bear. I sharpened my tools 4 or 5 times - maybe 6. I used CA to reinforce the end grain. I finally had a nice pen. I have never had another Coolibah blank act like that one.

It could be. The blanks have a lot of cracks and voids in it. The piece I bought was a 5x5x2 and I cut it down on a table saw into blanks. The one I turned yesterday with my new Woodchuck worked perfectly. I will see on the next ones I do if I experience any problems.

Thanks all!!!