john lucas
AAW Forum Expert
What I've learned so far. I have been playing with angles for quite a few years now trying to learn the what's and why's. It gets very complicated. Not the angles, that's easy. The more acute angles cut cleaner but don't hold an edge as long. More acute angles can be a little grabbier (if that's a word) if you aren't a skilled turner. For example when I was teaching more I learned that students had more catches with a spindle gouge ground at 35 degrees than one ground at 45. I don't notice much difference myself now but then I've been turning for about 35 years.
In actual use I will make a cut. If it doesn't cut the wood clean enough I will switch to a gouge with a more acute angle on the edge. Typically on bowls I start with my normal gouge which is 55 degrees ( or around there, I don't worry about exact angles, I'm looking for usable angles). If that's not cutting clean enough I'll switch to a 40 degree gouge. If that doesn't work my spindle gouge is 35 degrees. If that doesn't work I'll switch to the Hunter tool which has an angle about 27 degrees.
OK that sounds simple enough, BUT, if the bowl is deep you can't use the 35 degree gouge because the handle will hit the rim when you try to keep the bevel rubbing. That's where the Hunter tools come in, but I can talk about those in another article.
What I'm finding is there are lots of other factors besides cutting angle of the edge that affect the quality of the finished cut. If you force the cut, meaning pushing the gouge faster than it wants to cut, you get a less finished surface. Lathe speed. Slower speeds tend to make you force the cut easier. Higher speeds which can be dangerous of course, seem to help keep you from forcing the cut.
Tool angle. That is the way the wood crosses the cutting edge. When the wood crosses the cutting edge at 90 degrees you get a fast cut but a somewhat course cut. When the wood crosses the edge at an angle ( or skewed cut) you get a cleaner cut. The steeper than angle the cleaner the cut, but the tool cuts slower. So when your having tearout problems try looking at the cutting edge and see if you can rotate the tool to move the cut around the cutting edge so the wood passes at an angle. For example when rolling beads with a spindle gouge I usually start with the flute up and the wood at the top of the bead passes the edge at 90 degrees(we will call that 12 oclock) As I roll the tool over to cut the sides of the bead the wood is passing the edge at a slight angle so the sides of my beads would usually be cleaner than the top. I started rolling the gouge slightly for the beginning of the cut so the edge that starts to cut is about 11 oclock which is at a slight angle to the wood passing the edge. This leaves a cleaner cut. Hope that makes sense. I do grind my spindle gouges using the wolverine jig so the left and right edges roll around more than a lot of tool edges coming from the factory.
Edge polish. If you sharpen your tool to a finer grit you have a more polished bevel. This seems to affect the quality of the cut. I've been playing with different grits for sharpening and can tell the difference in the finished cut if i use a higher grit to hone or polish the edge. Of course if you really slow down the forward feed of the cut you get a burnished edge from this polished bevel. There seems to be a fine line between a clean cut and a burnished cut. If you sand afterwords it won't matter but if your cutting clean enough to not sand the finish may react differently to the burnished wood vs the cleanly cut wood.
Grain direction. It should go without saying but if you cut downhill with the grain you will get a cleaner cut than uphill against the grain. This is kind of what got me started playing with all the parameters above. When finish turning the outside of bowls so that I can finish the foot, I found that the last 1/4" or so has to be turned against the grain. You know that little section just before the foot where your gouge won't fit in either a push cut or pull cut. What I've learned now is I can usually go to my detail gouge that is sharpened at a 35 degree angle and clean up the last little bit so it requires little sanding. In fact if you combine all of the above, not forcing the cut, use a more acute edge, polish the edge, and cut with an angled or skewed edge, you may not have to do any more than touch it with 400 grit to finish the bowl. \
You'll notice I haven't talked about scrapers. I don't use them often simply because I can't get as good a finish. I'm not as skilled with them as Richard Raffen. I will use them when I haven't succeeded in getting as clean of a shape as I want with my gouges, however I don't claim to be an expert with a scraper. I'll leave that discussion to others.
Oh I'm sure there's more but my brain is still reeling from the last 9 days on the road. Thought I would give my take on this topic while waiting for the shop to warm up and then I'll sit back and read all the arguments pro and con later. Have a good day,
In actual use I will make a cut. If it doesn't cut the wood clean enough I will switch to a gouge with a more acute angle on the edge. Typically on bowls I start with my normal gouge which is 55 degrees ( or around there, I don't worry about exact angles, I'm looking for usable angles). If that's not cutting clean enough I'll switch to a 40 degree gouge. If that doesn't work my spindle gouge is 35 degrees. If that doesn't work I'll switch to the Hunter tool which has an angle about 27 degrees.
OK that sounds simple enough, BUT, if the bowl is deep you can't use the 35 degree gouge because the handle will hit the rim when you try to keep the bevel rubbing. That's where the Hunter tools come in, but I can talk about those in another article.
What I'm finding is there are lots of other factors besides cutting angle of the edge that affect the quality of the finished cut. If you force the cut, meaning pushing the gouge faster than it wants to cut, you get a less finished surface. Lathe speed. Slower speeds tend to make you force the cut easier. Higher speeds which can be dangerous of course, seem to help keep you from forcing the cut.
Tool angle. That is the way the wood crosses the cutting edge. When the wood crosses the cutting edge at 90 degrees you get a fast cut but a somewhat course cut. When the wood crosses the edge at an angle ( or skewed cut) you get a cleaner cut. The steeper than angle the cleaner the cut, but the tool cuts slower. So when your having tearout problems try looking at the cutting edge and see if you can rotate the tool to move the cut around the cutting edge so the wood passes at an angle. For example when rolling beads with a spindle gouge I usually start with the flute up and the wood at the top of the bead passes the edge at 90 degrees(we will call that 12 oclock) As I roll the tool over to cut the sides of the bead the wood is passing the edge at a slight angle so the sides of my beads would usually be cleaner than the top. I started rolling the gouge slightly for the beginning of the cut so the edge that starts to cut is about 11 oclock which is at a slight angle to the wood passing the edge. This leaves a cleaner cut. Hope that makes sense. I do grind my spindle gouges using the wolverine jig so the left and right edges roll around more than a lot of tool edges coming from the factory.
Edge polish. If you sharpen your tool to a finer grit you have a more polished bevel. This seems to affect the quality of the cut. I've been playing with different grits for sharpening and can tell the difference in the finished cut if i use a higher grit to hone or polish the edge. Of course if you really slow down the forward feed of the cut you get a burnished edge from this polished bevel. There seems to be a fine line between a clean cut and a burnished cut. If you sand afterwords it won't matter but if your cutting clean enough to not sand the finish may react differently to the burnished wood vs the cleanly cut wood.
Grain direction. It should go without saying but if you cut downhill with the grain you will get a cleaner cut than uphill against the grain. This is kind of what got me started playing with all the parameters above. When finish turning the outside of bowls so that I can finish the foot, I found that the last 1/4" or so has to be turned against the grain. You know that little section just before the foot where your gouge won't fit in either a push cut or pull cut. What I've learned now is I can usually go to my detail gouge that is sharpened at a 35 degree angle and clean up the last little bit so it requires little sanding. In fact if you combine all of the above, not forcing the cut, use a more acute edge, polish the edge, and cut with an angled or skewed edge, you may not have to do any more than touch it with 400 grit to finish the bowl. \
You'll notice I haven't talked about scrapers. I don't use them often simply because I can't get as good a finish. I'm not as skilled with them as Richard Raffen. I will use them when I haven't succeeded in getting as clean of a shape as I want with my gouges, however I don't claim to be an expert with a scraper. I'll leave that discussion to others.
Oh I'm sure there's more but my brain is still reeling from the last 9 days on the road. Thought I would give my take on this topic while waiting for the shop to warm up and then I'll sit back and read all the arguments pro and con later. Have a good day,
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