Posted on the general forum but thought I'd get some info here as well
Question for turners--Can a wood be too hard to turn. I have a piece of what I think is Australian pine. It's been sitting for a good 10 years. I decided to try making a bowl out of some of it. I cut a chunk off and rounded it on the band saw(pretty round) and mounted a face plate. I used a roughing gouge to round the outside. I could not get it to cut. The lightest pass gave me a catch.
I tried the top which is fairly flat.Same result What do you think? This stuff is very dense and heavyP
Jim, I would use a roughing gouge on a bowl form....the tang wasn't made for that kind of stress. Don't know about wood hardness you have, but I've turned some rough customers....biggest problem is the tool gets so hot, you cannot hold it.
SPINDLE roughing gouge is not a really good choice for flat grain bowl work
A deep fluted bowl gouge with the shank strength is a wise choice.
Some woods get really hot coming off the bowl gouge, and edges sometimes have a short run, but have never met a wood harder than high speed steel edges.
There's no wood that's as hard as high speed steel, and many tool steels are a good deal harder than HSS.
If you have a sharp tool and decent technique, it should cut. Some woods cut better than others, and some merely crumble, but if the mechanics are correct it will cut.
The hardest woods I've ever turned have been Leadwood, Snakewood, Lignum Vitae, and a few others that are much harder than anything that grows in North America. I have tried some woods that were loaded with silica or grit, which dulled the tools quickly, so I decided NOT to proceed, but if I kept sharpening, I could still cut them.
Just checking, but have you got the lathe going the wrong way? I remember not being able to start a cut one time, and discovered I had the lathe in reverse! Now, that won't cut, but its good for a laugh .
Sounds like you're cutting dry end-grain, and getting catches with that roughing gouge. First, try switching to a different tool...bowl gouge or scraper, and make sure your tool rest is as close to the piece as safely possible. Another thing that should help...drill a 1" diameter hole in the center of your blank, to the desired depth of the bowl. Then approach your cuts from the side-grain.
I recently turned some very old white oak (I think). The wood came from a log cabin built just after the revolutionary war. I turned some scoops at pictured and some small bowls. My gouges barely dented the wood. Even using the Glasers (A11), Hamlets (1060) and a Thompson tool, I could not pick up cuts. I ended up scraping the bowls round and scraping to hollow them. I think the wood must have a very high silica content that is dulling the tools. That's all I can surmise. Joe
Ray Thompson gave me some white oak that had been offered to a buyer for a well known oak outlet. The buyer did some sort of test on the wood and declined to buy, saying that the mineral content was too high. he was right. This stuff was HARD. Not as hard as Australian Ring Gidgee, but very close. I have turned leadwood, snakewood, iron wood, lignum vitae ... and none were as hard as this white oak. I sharpened often ... take a cut, sharpen, rinse lather repeat ... wait that's for my shampoo ... cut, sharpen repeat, repeat repeat ... Eventually got there, but had to take light cuts and sharpen much more frequently that any other wood ...
>>>I think the wood must have a very high silica content that is dulling the tools. That's all I can surmise.
Joe, I wondered about that on some very old wood I have. Someone gave me a thick walnut plank from a very old house, said to be a mantel possibly 100 years old. I haven't turned any but it dulled a brand new Starrett bimetal bandsaw blade in short order: one crosscut and a couple of rip cuts. I have NOT tried turning this but after this discussion, I think I will.
Can wood get harder just aging? Can the "slica content", or whatever it is that dulls tools, increase with age?
I found this in an interesting article:
6. All clean woods which quickly dull tools share the property of being dense and heavy. There are no light woods which dull tools. Osage orange dulls tools because it is an extremely dense and hard wood. Ditto for black locust.
7. Some forms of silicon are water soluble and can move within a tree’s transport system and some of these silicas can interact with endogenous chemicals and result in deposits of silica compounds. This is not a common situation.
8. These deposited silica chemicals are probably (?) not hard crystals -- think more like table salt -- and are not especially dulling to tools. This is a shaky “fact” and subject to modification as the definitive investigations are conducted or uncovered.
Info from Rob Wallace, probably the same WoodCentral Rob. The article is here:
Did the turning attempt destroy the sharp edge of the tool? That would be a hint.
There are two woods I've turned which certainly destroyed the edge of tools: root burls that contained rocks and dirt, and a piece of a pier submerged in salt water for an unknown long time and containing voids from worms and parts of shells. Then than that, I've never found wood I couldn't turn. I prefer to turn hard woods, the harder the better. I have turned a number of pieces a kind gentlemen from Australia sent to me. He warned me it might be too hard to turn but I had no issues. Sharp tools...
Besides the documented danger of breaking a tang of a spindle roughing gouge on bowl blanks (I've seen broken tangs, heard of injuries), I think another reason the tool is not appropriate is the cutting edge is simply too wide. Many roughing gouges have a shallow curve 3/4" or wider which simply presents too much wood to the tool at one time, especially when pounding against the end grain twice each revolution. (On spindle work it is always cutting side grain.) A 1/2" or even 3/8" bowl gouge is much "gentler" and only removes a small, more controllable amount of wood at once. Also, I didn't see where you mentioned your technique, but just in case: presenting any tool directly into the outside diameter of a rough bowl gouge will give me a beating. With a bowl gouge, I learned to start at the face near the "corner", trim down to solid wood, then cut across the side of the blank towards the headstock, a little at a time if necessary. This way you are always cutting side grain rather than end grain. Works for me.
Question: can you cut it with a sharp chisel and mallet? If so, I think it can be turned.
BTW, I can't find any wood with that name, but there is an Australian Cypress, Callitris glaucophylla sometimes called white cypress pine, from the Wood Database, "...one of the hardest conifers in the world, rivaling some species of Yew (Taxus spp.) found in the Northern Hemisphere."
However, the reported Janka hardness is only 6,060 N. Compare that to 19,510 N for Lignum Vitae which is fun to turn. But with wood common name confusion all over the world, who knows what species it actually is.
An option if you give up on the bowl: slice the blank into smaller pieces and do some spindle turning! Just think, instead of one bowl you can make a dozen things!
Hey, do you know some other turners in your area who could try cutting on your blank? Or here's a great idea, if you give up send it to me. I would love to try some "Australian Pine" or what ever it is.
Not sure if the tool was just dulled quickly or not because I did not take it to another species to compare. I would get maybe one cut then nothing. Joe
These are the Delrin scoop jaws I made to turn the scoops I posted last week. I bought a slab of 1" thick Delrin on Amazon and cut the pieces on the table saw. There are four views shown. Side, Top (you can see that I slight hollowed the inside of the jaws), minimum span and maximum span. The chuck is a Vicmarc VL100. I can get the jaws to close down more if I shave some more material off the diagonal cuts in the interior where the 4 jaws meet. I use a band clamp to tighten it all down because the delrin is slippery and the scoops can still move with just chuck pressure. The blocks are cut 3" tall and 2" wide. The handle just sticks out between the jaws.
Hey Dick, The four scoops came out ok. I did not notice any flexing, but I know that they moved a little because I could move the orb in the socket with a little force. At first, I wrapped tape around the jaws. That worked sort of. When I switched to the band clamp, the scoops were rock solid.
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