Finishing Cuts on the
Insides of Bowls
I use any one of several ways to get aa finish cut on the inside of a piece. Which is better depends on the wood. If anyone wants more discussion on any one of these, ask, and I will elaborate. [EDITOR'S NOTE: Russ is no longer with us, so please don't ask.]
All of these tools are a bit different from the normal, and I recommend a trial run at a very slow lathe speed so that you can get used to the tool and see how it cuts before going blind on the inside of a bowl.
1. Ride the bevel, but grind the bevel of the gouge to a convex curve so that there is one there to ride on. The flat or concave curve off the grinder makes the tool contact the wood at the cutting edge and the heal of the bevel, and there is no pressure on the wood behind the cutting edge to hold it down while it is being sheared. This bevel should only be 1/16" wide so whether it is flat or concave is close enough. I grind this by hand and don't worry about multifacets on the bevel because the wood only sees the one next to the cutting edge. This shape works better than the normal concave bevel on almost all wood. Since it is difficult to grind, I only use it for those that can be difficult, soft and/or spalted.
2. For shallow forms, bottoms, and flat surfaces I grind a gouge that is flat across the end with no side grind, and as little bevel as possible. I set up the tool rest so there will be about 1/32" difference between the edge and the heal of the bevel. Then hold the gouge square to the face of the wheel, and rotate the bevel across the wheel. This works best when there is a minimum of curve to the bevel, so an 8" wheel is better than anything smaller, and a 5/8" diameter tool is better than a smaller one because the bevel is wider.
I set the tool so the bottom of the flute is on the centerline while the gouge is held flat (level with the lathe bed). Then rotate the flute to somewhere between 45 and 90 degrees into the wood, ride the bevel and raise the tip (lower the handle) slightly to initiate a cut across the bottom of the flute. Light cuts only, but the cutting action is similar to that of a skew chisel on a slindle cut.
3. Grind a micro-bevel on the scraper, and then tilt it up into a shearing cut across the edge. I make the micro-bevel by grinding the edge at about 75 degrees (included angle), and then remove all sign of a burr by using a stone on the top of the tool. Then hold the stone at 90 degrees to the top surface and draw it down across the cutting edge, lightly and no more than 2 or 3 times. You should have a very fine burr on top of the scraper and it will have the same surface as the grit of the stone that was used.
This is not an aggressive tool, and very light cuts are possible without large forces on the wood. Here is where a polished edge on the toolrest will be appreciated.
4. Grind a shallower bevel on the tip of the bowl gouge. I normally use a Wolverine jig to make a very long side grind on a bowl gouge, and its tip angle is normally about 80 degrees (included angle). For this tool I change the tip angle to about 55-60 degrees. The gouge is used with the flute turned into the wood, and then ride the bevel into the bowl. The sharper angle will make more of a shearing cut. It is not good for other than light finishing cuts because the shallow angle is very "grabby". This tool works very well for natural edged bowls from Walnut or other woods that tend to have a lot of tear-out on the shallow end-grain cuts.
The gouge is ground more like a blunt spindle gouge than a traditional bowl gouge, and a spindle gouge with a moderate "fingernail" shape and a 60 degree (included angle) bevel will work as well. But, I prefer the long grind on the bowl gouge because the long edges make excellent scrapers. To grind this edge, I usually start with a gouge that has already been ground is nearing the end of its useful life. I set the leg on the jig for grinding a spindle gouge so that the bevel behind the tip rolls back across the top of the flute. Otherwise, the long edge behind the tip will be very thin and sharp. The tool rest is adjusted so the tip angle is about 55-60 degrees (included). The long edges can also be ground back by hand.
I hope that all of this may be of some use. These cutting edges work for me, but that is not a guarantee that they will do the same for you without some practice.
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