grind angles

"B" has a limited tool life

Geoff Whaling

Apart from the self feed aspects of the grind angles from a purely tool maintenance and sharpening aspect profile "B" has a limited tool life. As the nose shortens the profile will eventually migrate towards profile "C".

Re: "B" has a limited tool life

David Gilbert

The scraper in A appears to have an included angle of 90 degrees. I used a negative rake scraper with this profile and it worked pretty well. I was told by Stuart Batty that they will work even better when the included angle is less than 90 degrees. Once reground to less than 90 degrees I found that Stuart was correct.

Cheers,

David

Re: grind angles

Dennis in Southern Oregon

Keith, it seems to me that if you are using these gouges in the normal bevel-rubbing mode, there is no functional difference between B and C provided the nose angles are the same. You just have to hold the handle in slightly different angles to get the bevel to rub in the two cases.

Re: grind angles

Keith Tompkins

Dennis, I thought the same thing, but it makes a difference. It may make no difference if cutting only with the tip, but I seldom do that. With grind B, you must hold the handle above horizontal at all times, otherwise, the tool catches; and it will catch when least expected, especially if cutting with the side of the bevel. I discovered this unfortunately during a demo, when I was hollowing end grain freehand quite a distance over the rest. I did a quick resharpening during the cut, and immediately the tool was grabbing and catching. So badly, I cut through the side of the piece I was turning. Not good at all, and totally unexpected. When I got home, I examined the cutting tip; it was running uphill as in "B". Could this be the problem? I reground as in "C", and the problem was solved. In the two years since, I've tried all kinds of grinds and angles....I won't grind anything that runs uphill again. I would be interested if you grind the shapes and get back to me.

The upward hook angle cutting edge .......

JamieDonaldson

... in example B would obviously be very "catchy" regardless of handle angle or bevel rub. I don't know of any tool in that configuration that would be safely usable.

Re: The upward hook angle cutting edge .......

Keith Tompkins

I think you are right Jamie! Even the slightest amount of hook makes a big difference. Even FLAT like a normal scraper has an effect.

burs on scrapers

Geoff Whaling

Isn't that what you create when you "raise the bur" onn a scraper?

True indeed Geoff, and most scraper users......

JamieDonaldson

...elevate the handle heel to reduce the hook angle to more of a negative rake action. The burr on a scraper usually doesn't last long in use, and turners who attempt to rub the bevel are courting disaster!

Re: grind angles

Dennis in Southern Oregon

I am a bit confused as to the overall shape of the tool. What is the profile as viewed from the top? Is the slope shown in the side view ground longitudinally or does it run all around the end of the skew? Do you have a picture?

Re: grind angles

Keith Tompkins

Hi Dennis, the tool I'm referring to is the center image. The tool below it is my Thompson detail gouge as a reference. With my fluteless gouge (skewji-gouge variation) the cutting edge faces downward, and the bevel is very small.

Re: grind angles

Brad Vietje

I wonder what difference it would make if "C" was ground with a flat bevel, instead of a hollow (concave) top? I don't think that would be quite the same as "A". If C were sharpened on a sanding disk or belt sander, the top surface would be flat.

Safe spinning,

Brad Vietje

Newbury, VT

Re: grind angles

Keith Tompkins

Hi Brad, I think grinding a flat in "C" would work fine as long as it slopes downhill. The trick is to get the cutting edge way down on the tool, as opposed to a conventional gouge, where the cutting edge is high up on top.

Re: grind angles

john lucas

I played pretty extensively with flat bevels vs concave. Very little difference. If you hone an edge there's no difference because you hone tiny flats on the edge so the wood doesn't see any difference.

It all started years ago when I was reading about Japanese chisels. We all know how good those guys are with a chisel. I worked very very hard flattening my chisels. There was virtually no difference for how I use a chisel. I do sharpen a micro bevel on my chisels after grinding the concave angle

when I did my skew testing I ground flat, concave and convex. I found very little difference in how they handled. For any of these tools it's more about the presentation of the tool to the work and how skilled you are that seems to make the most difference.

Re: grind angles

Keith Tompkins

But John, you are exploding the "just one more tool" myth!