Thread: More on shear scraping

I have done some experimenting using shear scraping with 3 tools on some pine scrap.

The curved scraper was the easiest to use mainly because it's easy to see. It removed most of the tear-out but there was still a remnant that would not budge.

The bowl gouge gave the best result, the remnant mentioned above was almost entirely removed but did leave a number of concentric tool marks which required 120 grit sandpaper to remove.

I also tried a spindle gouge because it was handy, I kept getting catches as the nose of the fingernail shape kept hitting the timber. When it wasn't catching, it produced a reasonable result but I found too difficult to use on a regular basis.

Originally Posted by tea lady

I usually sand with the lathe turned off after the initial sanding. Just to get the reversed grain sorted out. (Cos I haven't got a reverse switch on my "home" lathe.) sand with the grain by hand. I find you only need to do it on the first grit. (80# for mere mortals. Only Ken W starts with 240# )Then you can turn the lathe on again to complete the sanding.

Hope to clear it all up at the turn on. Failing that we could get together some other time. If you are still struggling.

Another thought is that sometimes with blackwood I have had patches of what seems to be hard toasted areas. Only surmising here but I think sometimes if blackwood gets hot sap or something in it goes hard, and becomes impossible to sand. Ya have to go back to the chisel to get rid of it. I've never heard others mention this though, It could be my imagination. So go easy with the sanding pressure, and if the paper is getting hot move to a new spot on both the paper and the bowl. The heat kind of means that the paper is more rubbing than sanding anyway. You can get hard patches of sap on radiata too.

Hope my thinking out loud helps.

Thanks, Tea Lady. You may be right as the timber sometimes has hard and soft patches and that could be contributing. I'll try and make the turn-on and if not, we'll see what we can do. A reversing switch would help but that would take a fair bit of effort to install on my lathe.

Tiger,
Do you round off the heel of the bevel on your gouges? This really helps on the inside of the bowls. If you leave the bevel as is off the grinder, the sharp heel can actually leave burnish/bruise marks in the wood. It also, on the inside of the bowl leave the bevel much farther from the cutting edge due to the concave shape of the bowl. This is why you don't have this problem on the outside of the bowl. The sharp heel can actually push the gouge into the cut which is why you get the concentric rings. I grind about half of my bevel off, and have recently discovered that I get a better cut on the inside of the bowl if I use a smaller gouge, like 1/2 to 3/8 inch. I figure this again is having the bevel closer to the cutting edge.

robo hippy

Originally Posted by robo hippy

Tiger,
Do you round off the heel of the bevel on your gouges? This really helps on the inside of the bowls. If you leave the bevel as is off the grinder, the sharp heel can actually leave burnish/bruise marks in the wood. It also, on the inside of the bowl leave the bevel much farther from the cutting edge due to the concave shape of the bowl. This is why you don't have this problem on the outside of the bowl. The sharp heel can actually push the gouge into the cut which is why you get the concentric rings. I grind about half of my bevel off, and have recently discovered that I get a better cut on the inside of the bowl if I use a smaller gouge, like 1/2 to 3/8 inch. I figure this again is having the bevel closer to the cutting edge.

robo hippy

Thanks, Robo, won't be hard to do so I'll give it a try.

Somebody explained about grinding off the bottom of the bowl gouge many years ago to me because I was having the burnished ring problems on the inside of my bowls. It works great. Over the years I 've gotten to where I grind even more away so there is a moderately short main bevel. The main reason I do this is it makes sharpening faster because the bevel is shorter and your removing less metal. It really works well if you use a diamond hone.
I've been experimenting with convex bevels for turning the inside of a bowl. Johannes Michelson uses this grind for his cowboy hats. His grind doesn't have any concave or flat areas. It's totally convex. It's interesting using this grind. There is a video on U-tube showing how to sharpen it. I'll see if I can find it and post it if anyone is interested.