The bowl gouge is manufactured to very high standards and is probably the most used tool owned by many turners. In the past, the tools were hand forged from carbon steel and came in all shapes and sizes. Today we have quality M2 HSS (High Speed) steels that give us a tool that takes and holds its edge for a lot longer. In addition to the HSS steel there is also Powder Metallurgy (PM). PM is a metal-forming process performed by heating compacted metal powders to just below their melting points.
Gouge made for HSS steel will have a hardness between 62 to 64 degrees Rockwell, and a Gouge made from PM steel will have a hardness between 66 to 68 degrees Rockwell. Keep in mind that the alloys used in making HSS or PM can vary which lead to different variations of hardness. The hardness quoted above is from Crown Tools who manufacture Woodturning Tools in Sheffield England.
A typical bowl gouge is manufactured from solid bar with a deep flute milled along two-thirds of the length of the bar. The flute is milled in such a way that the shavings will be ejected from the tool without clogging while making a cut. There are some profiles however, that have quite narrow flute profiles and these unfortunately have a tendency to clog up with shavings created by the tool.
Bowl gouges normally have much longer handles than spindle turning tools to allow the user better control. They also have deeper flutes in relation to the bar size than a spindle gouge. They can be ground in a variety of ways; from square to a swept-back grind of varying degrees. These are often referred to as: Celtic/Irish grind, Ellsworth grind and long-grind bowl gouges. There are also many other names for these grinds. Individual turners have their own personal variations on these for various reasons; no grind is right or wrong.
“Rub the bevel”, turners often use this term, but I wonder how many truly understand what it means? My understanding is that the tool at its cutting edge requires bevel support to allow the tool to cut in a controlled manner. The amount of support relies upon how heavy the cut is: if it is a light cut then less bevel support is required. As the cut becomes heavier, the amount of bevel support required is increased as the edge cuts deeper into the wood. The edge has to submarine below the surface to achieve a cut. The depth of cut is limited by three elements: bevel length, lathe power and the ability of the turner. The amount of true bevel contact is actually much less than expected; the resin build-up just behind the edge is the actual amount of bevel contact that has occurred. The “dreaded catch” is a result of insufficient bevel support for the attempted cut. The gouge should be presented to the turning at the same angle as the bevel is ground this will allow much greater control.
My favorite is a 5/8″ gouge with a Ellsworth grind, which has been modified. I use a 60 degree grind and roll the top of the wings in slightly towards the center. This allows me to rub the bevel at a flatter angle and then turn the gouge slightly to start the cut, either left or right.