Anyone have opinions about why green wood dulls gouges (M2, M4, and Kryo M2) and band saw blades so fast relative to the same wood dry? One would think that the water would cool and lubricate the cut versus dry wood, but still it appears as if tools dull much faster. I work mostly with English Walnut, "Black" Walnut root burl and Western Maple. Perhaps having a scary-sharp edge is just more critical to sever the wet fibers...I don't know. Do you?
This group has never been short of people with opinions (albeit some more reasoned than others) so I thought I'd ask to see if anyone has a reasonable explanation.
My experience has been the resin buildup on the tools. When I have turned really green or wet woods, the heat seems to dry out (cook?) the resin from the sap onto the tools. Just like a saw blade, a resin encrusted cutting tool is its own worst enemy because as the resin builds, it generates more heat. As the heat rises it cooks more resin onto the cutting edge.
I always keep a large cup of water next to the grinder, and when I turn really wet woods I dip the tool into water and wipe before getting resin into/onto my grinding wheels.
I agree with Darrell-there is abrasive material in the bark. When the bark is cut away, I resharpen and find that with the woods I usually work (various Ozark region hardwoods), edge life is longer than for dry wood in the sam species. And the shavings hittin my hand are a lot cooler!
In my experience, most green woods are easier on the tool edge than dry wood..
As to the bark, it would seem that if there IS a difference, wet would be easier on the tool if there is sand, etc. in the bark, as it wouldn't be as "set" in the bark?
My first 2 tools when turning green wood with bark on are the stud finder and a
2" roughing gouge..
You sort of want to avoid nails, barbed wire and assorted stuff that is often in branch or trunk wood... It's a "no drama, no trauma" kind of thing.....
A few years ago, I bought the Benjamin's best 3 piece bowl gouge set from PSI and it came with a 2" gouge that looks like a huge dog food scoop... About the only thing I use the monster for is taking bark off stuff because it's big, heavy and ugly and I don't care if I hurt it..
I have never noticed that wet wood dulls tools faster than dry wood. I turn green wood almost exclusivly, but notice a big difference in dulling turning tools when I do the occasional dry piece. When cutting green wood on the bandsaw, I think green wood cuts with less resistance, as long as you have a sharp blade with the proper tooth set and gap. Dry wood cuts more slowly, but will cut better with a different tooth set than my usual resawing blades.
The biggest difference in dulling seems to be the woods. The prettiest myrtle wood comes from the Oregon and north California coast. It can dull the tools more quickly than other woods. My theory on that is that it has a higher silica content than most other woods because growing on the coast, it sucks up a lot of micro particles of silica/ sand.
I have noticed that the walnuts (English, Black, and Butternut) seem to dull the tools rather quickly for woods that aren't that dense. I have suspected that since they are acidic in nature, that the acid could be the culprit, like George said. I suppose Oak will do the same thing, but I almost never turn oak.
Density of the wood does contribute, and I haven't realy noticed that bark contributes, if it is clean. If it has been laying on the ground, then it picks up grit.
With the different grades of steel, I have noticed little difference in the time that any steel will hold the 'fresh off the grinder' edge. The harder steels will hold the 'I can still hog off a lot more material' edge than the M2 does.
All of this is theoretical, just observations that I have made.
Seems unlikely the tree could transport particulates, though soluble silica compounds may be metabolized into less soluble or insoluble types. One common mineral stain in our local woods is calcium oxalate, the stuff of the common kidney stone. It will dull tools, that's for sure.
I'm sure others have noticed that trees which retain branches for a long time often have greenish stain in the convoluted grain on the ground side of the branches, where a less-soluble compound would naturally slow along with the reduced flow to the crown. I rather suspect this is the same calcium oxalate. Our common eastern white cedar is one which has both green and the dulling effect. Proportionate, I don't know. Never paid that much attention. I sharpen when the tool is no longer cutting cleanly.
Funny that you should mention that, Reed... A friend that lives in Alaska stopped on the Oregon coast on his way here and brought me a bag of myrtle wood pen blanks.. I'm looking forward to playing with them, they sure are pretty wood..
I turn a lot of walnut and maple and find the exact opposite: dry wood always dulls tools faster, unless the bark is still on, and then I suppose it's dirt in the bark. Band saw blades are another matter, but the only time I have fast dulling problems with bandsaws is with sapwood, and I'm not sure it's dulling so much as clogging up the blade with sap. Maybe try cleaning the tool edge when you think they're dulling quickly and see if it's not just a tiny bit of buildup at the edge?
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