Double-beveled gouges?

[rsser]

Along The Bevel - The Woodworkers Institute (http://www.woodworkersinstitute.com/page.asp?p=1222)

From memory Eli Avisera uses a small 2ndary bevel for bowl outsides, and the pictures of gouge grinds on Wood Central includes one with a convex 'bevel'.

(The curse of variation in terms: with flatwork chisels I call the 2ndary bevel the small steeper bevel at the tip; O'Donell uses the term differently but it's clear from the pic series what he's referring to.)

The question arises of how much of a problem is caused by a single bevel off a bigger diameter wheel; 8" wheels seem to be common in Aus. and Tormekers have the benefit of 10" (T7). So there's less concavity in the bevel.

[tea lady]

:S The problem seems to be using the wrong tool! Why use a shallow fluted gouge when he usually used a bowl gouge which did the job perfectly? And a shallow fluted gouge for coves? :doh: Just use a spindle gouge. :rolleyes: Shallow fluted gouges are great for hollowing end grain boxes, where nothing else does the job as well. :cool: And you want all of that long bevel.

[rsser]

Terminological probs again. Some turners use the term shallow-fluted gouge to refer to what I call a spindle gouge.

If it has a very shallow flute it seems 'detail gouge' is often the label.

Apart from that, one reason for using a shallow-fluted gouge when a bowl gouge might do is that you get more steel for your money.

[NeilS]

Played around with secondary bevels on gouges for the inside of bowls. They work well, but no better than a smaller gouge. Now I just use the same single bevel angle on all of my bowl gouges. It's simpler and quicker. No mucking around changing grind settings.

I like the idea of a flat grind, but like my 8" diamond wheel too much to consider changing to a flat grind.

[dr4g0nfly]

Turners have always used a grinder of some sort to sharpen their tools (honing of skews not-withstanding).

The presentation of the cutting edge and the use of the bevel behind it is something we all understand.

When we start to learn to turn we 'Rub' the bevel and although the term persists, we soon learn that the 'Rub' causes the bumps and ripples Mick shows in the images.

Hence we adjust our tool presentation to present the cutting edge and caress the bevel.

If we were to use the concavity of the tool grind, the bigger problem would be the dragging of the trailing side of the grind across the workface.

As we progress as turners we learn to adjust the angle of the tool presentation to give the Cut and without active thought on our behalf, to use the natural springiness of the wood to microscopically deflect under the tool and provide the Rub (caress) on a tiny area of the bevel behind the edge to provide the burnish.

[rsser]

Turners have always used a grinder of some sort to sharpen their tools (honing of skews not-withstanding).

Mike Darlow was a big advocate of belt sharpening and the Sorby ProEdge has something of a following.

Maybe a more accurate description of what O'Donnell found works better for him is a shorter straight bevel and ground-away heel.

[robo hippy]

The secondary bevel makes no difference on a convex shape like the outside of the bowl.With the convex shape, you can not rub the heel of the bevel, and it makes no difference if the surface of the bevel has the grinding wheel concave shape or not. The bevel is rubbing, very gently, very close to the cutting edge. By keeping the rubbing spot close to where the tool is cutting, the tool and cutting is easier to control.

When you you get to the concave shapes, then the heel of the bevel will rub. A sharp heel will actually kind of dig in and push the cutting edge into the wood. The sharp edge will also bruise the wood, and much more so if the wood is green. This is why we 'relieve' the heel of the bevel. Bevel angle determines how well you can move down the side of the bowl, through the transition, and across the bottom of the bowl. Again, this keeps the cutting edge closer to where the bevel is rubbing.

Smaller tools have smaller bevels, so, again, the cutting edge is closer to the cutting edge, which is why a lot of people like smaller tools for making the finish cuts. I do use them some times, and I still relieve the bevel.

robo hippy