Author Topic: Scrapers  (Read 5442 times)

Offline richinva

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Scrapers
« on: April 26, 2006, 11:49:24 am »
Hi guys,

What procedure do you use for bowl scrapers?  I tried as the book indicated, but recently turned the UTS to the "front", with the stone turning away from the edge, hoping to raise a burr that way.

Do you utilize some type of burnishing device or use the tool straight off the Tormek?  Have had one fellow tell me he uses the Veritas burnisher with great results.

Thanks.

Rich

Offline Jeff Farris

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Re:Scrapers
« Reply #1 on: April 26, 2006, 07:15:13 pm »
I do scrapers in the horizontal mount, too. You do have to concentrate on keeping the tool down on the TORLOCK tool rest, but I prefer this to the chatter and increased stone wear that you get in the vertical mount.

The ground burr is superior to the burr that you would get from a dry ground method. If you plan on pulling a burr with a burnishing tool, it is important to take the tool to the leather honing wheel and polish off the ground burr.

But, what is "best"?  That's a tough question.  The ground burr from the TORMEK is cleaner and sharper than any ground burr out there and I think it is nearly the equal of a pulled burr.  I find a pulled burr to be somewhat difficult to control. It is often more aggressive than I want it to be, even when I am using what I think is a very light touch.  If you can control it, a pulled burr leaves a very, very nice finish on face grain projects. For me, the extra step of removing the burr and then pulling one with a burnishing tool doesn't give me enough improvement in results to make it worthwhile.  For face grain projects, I polish the flat side of the scraper to a mirror finish, sharpen it in the horizontal mount, with the grindstone graded to the fine finish and go straight to the lathe with the ground burr.

But, here's a curve ball.  If the grain is oriented so that you are finishing an inside surface of end grain (trunk of the tree parallel to the lathe bed and working on the end of the project -- like a goblet would normally be), I don't use any burr at all.  I found this tip in one of the British wood turning magazines a few years ago, and found it to be very successful.  If you have something like the TORMEK leather strop available, you can get a far superior finish in end grain scraping by polishing the face (flat side) of your scraper to a mirror finish, grinding the bevel very fine (fine side of the stone grader), and then polishing off the wire edge and polishing the bevel side, too.  Try it both ways on end grain -- with and without the burr.  I think you will see a dramatic improvement in the surface finish without the burr.

One more note on scrapers. It is important to learn when to use them and when not to use them.  Lots of folks use them on long grain (spindle work - between centers) projects. While they will cut there, a far superior surface finish will be achieved with gouges and skews -- provided that you always work with the bevel riding.   Scrapers are finishing tools, not stock removal tools, and should be used on face grain cuts and end grain cuts only.  If your long grain project needs scraping, you didn't use your gouges and skews correctly.
Jeff Farris

Offline richinva

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Re:Scrapers
« Reply #2 on: April 26, 2006, 09:55:24 pm »
Jeff,

Thanks, just what I was looking for.

These are for end grain of bowls only.  Most, and I stress the word most, of the spindle work now is pretty nice off the tool, especially when the skew is fresh off the Tormek............ :)

I'll try your way, have a Honduras mahogany bowl on the chuck as we speak that has some wicked end grain..........

Will let you know how it turns out.

Rich

Offline boehme

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Re:Scrapers
« Reply #3 on: June 08, 2006, 11:44:42 pm »
"Really concentrating" is an understatement!  No matter how hard I concentrate, I almost always seem to let the stone grab the scraper if I try grinding in the horizontal position -- and then I have a really big dig in the stone.  Maybe I am applying too much forward pressure.

Bill