skew vs negative rake scraper

Re: skew vs negative rake scraper

Ralph Lindberg

I've been sharpening my "french curve" negative scraper at the same angles as my skew.

I think it works well, I like the reversibility, but note the edge appears to go dull faster then when I was grinding it as a conventional scraper.

Re: skew vs negative rake scraper

robo hippy

I have been playing a lot more with burnished burrs for my shear scraping, all Eric Lofstrom's fault... I had already found that a high shear angle cut with gouges sharpened on a 1000 grit CBN wheel can clean up a lot of tear out that would not clean up with the same tool sharpened on a worn in 180 grit CBN wheel. The hand honed tools did not cut as well. I am finding that the burnished burrs on scrapers are doing pretty much the same thing, but that burr is very strong and can be used for roughing cuts. A NRS is still a scraper, and on harder woods does a fairly good job, but still, the shear scrape seems to give the cleaner surface, with the exception being on end grain, or across the bottom of a bowl, but not up the sides of the bowl... I use a hand held 3/16 micro grain carbide rod in a handle... The more I use it, the more I like it...

robo hippy

Re: skew vs negative rake scraper

Dennis in Southern Oregon

Robo, could you explain the bit about the carbide rod?

burnishing scrapers

John K Jordan

Reed, We've discussed this in the past - I burnish every scraper with a carbide rod since I got my first scraper long time ago. (I mounted mine in a nice rosewood handle. ) At first I used the Veritas burnisher with carbide pins but that isn't much good for gouges and the small-angle negative rake scrapers in wide use now.

As you mentioned, the burr lasts a long time unlike a grinder burr. It's more like a sharp cutting edge. The rod is traditionally used on cabinet scrapers to burnish a cutting edge so using it on turning tools was a no-brainer.

I did try the burr raised by the 1200 grit CBN wheel on my Tormek. A few days ago I compared the burrs raised by the rod, a hand held flat diamond hone, and a round tapered hone held and used just like the carbide rod. The carbide rod worked the best for me for shear scraping with a gouge and NRS. Under the microscope the burnished burr looks like a smooth knife edge while the burr from the grinder looks like a row of jagged teeth ready to get knocked out.

For the best shear scraping, I grind a fresh edge with the 1200 grit Tormek wheel, remove any burr with the Tormek leather honing wheel polishing the edge a bit, strop the tool on flat leather, then make one swipe with the carbide burnishing rod. It doesn't need much pressure to roll up the burnished burr. After some use I may replenish this burr, usually after honing the edge with an extra fine (blue) Eze-Lap diamond hone. I use the same method with gouges for shear scraping, negative rake scrapers, conventional non-negative rake scrapers, and card/cabinet scrapers.

BTW, I love the edge the 1200 grit CBN puts on a cutting tool. I mostly use it on the spindle gouges.

JKJ