Finishing with a scraper as opposed to sandpaper...

[Alan Carruth]

Michael Lewis asked:
"...what would be wrong with sharpening your scraper by stoning the sides on a diamond block? "

Nothing, if you had the time. You'd have to lap away about .001" of fully hard tool steel to get the edge back each time.

I do touch up the edges by lapping the burr off the surface, and then standing the scraper up on a diamond stone and rubbing it to make a flat on each side of the hollow grind. This gives a nice light, sharp edge for final scraping on soft wood, for example. There's no reason you could not simply keep sharpening the thing that way, and avoid the grinder altogether, but it's hard to keep the edge perpendicular with no hollow. Perpendicularity id not a shibboleth, of course; it's just nice in that the edge will be about the same on both faces.

Alan Carruth / Luthier

[Michael Lewis]

Thanks Alan.

[Arnt Rian]

Alan, you say on the SM instructions to "Use as fine a wheel as possible". The finest 6" (white) grinding wheel that Norton makes is 150 grit, I think. Is this about right, or should it be finer (or coarser)?

[Steven Wilson]

Just got my new scraper last week, very nice job Alan. I've all ways used home made scrapers from spring steel and saw blades. I really like the heft of it, I can very effectively scrape with one hand. I was wondering if there was a reason for the hollow grind one the side. Or is it just for ergonomics?
Thanks
Steven

[Michael Lewis]

The hollow grind gives a slightly more acute angle to the cutting edge.

[Chuck Tweedy]

I think Steven is asking about the hollow sides to the tool.
I assumed it was to make flattening the sides easier. Minimize the amount of material you need to remove to true up that surface.
Like a Japanese chisel.

[Alan Carruth]

Arnt Rian asked:
""Use as fine a wheel as possible". The finest 6" (white) grinding wheel that Norton makes is 150 grit, I think. Is this about right, or should it be finer (or coarser)?"

I just use the finest one on my grinder, and offhand I can't tell you what the grit is. When I want a really fine edge, say for scraping a violin top, I'll de-burr on the diamond stone as usual, stand the scraper up on the diamond stone, and rub around the edges to make a new, fine burr.

Steven Wilson asked:
" I was wondering if there was a reason for the hollow grind one the side. "

Chuck Tweedy got it. These scrapers are hardened, but not tempered, so there's usually some stress introduced by the heat treatment that's not subsequently relieved. The folks who make them use a centerless grinder to level the surface pretty well, but it's never perfect, as the steel will keep on moving for a while. Lapping off the entire surface is time-consuming, so the hollow in the center helps a lot. Besides, it's nice to hold on to. The next generation of these scrapers should have wider 'land' on the straight side, to allow for more sharpenings.

Alan Carruth / Luthier

[Michael Lewis]

Alan, at the rate most folks use and sharpen scrapers the current model you offer should last a lifetime, why worry about making it last even longer?

[Alan Carruth]

Michael Lewis asked:
"Alan, at the rate most folks use and sharpen scrapers the current model you offer should last a lifetime, why worry about making it last even longer?"

I use my scrapers a LOT, and have reduced the size of a couple of them noticeably. These things get a lot more use on archtop instruments: if you don't make those, you might be surprised. Anyway, it's just a matter of trying to get the most value out of the piece of steel.

Alan Carruth / Luthier

[Mario Proulx]

I have about a dozen scrapers on the fly at any given time, and some of the oldest ones are at least 1/2" narrower than they started out as... Yup, they wear!

[Martin Keith]

Just chiming in here about Alan's "Ultimate" scraper...

I had the good fortune to use one of these at Ken Parker's shop and was really pleased by the utility and comfort of this tool.

This really is a great little tool, and I'll use it often.
Beyond the advertised applications for scraping archtops, it's useful for tons of different little scraping tasks.
I'm looking forward to scraping some binding this weekend - a feeling I don't often have about that job!

Thanks to Alan for bringing this to everyone's attention!

Best,
Martin

[Alan Carruth]

Mario wrote:
"I have about a dozen scrapers on the fly at any given time, and some of the oldest ones are at least 1/2" narrower than they started out as... Yup, they wear!"

I made my first heavy scraper out of an old power hacksaw blade after my favorite card scraper got too narrow to use, and I couldn't find another one with the same feel. I'd seen Carleen Hutchins using the heavy one for years, and just never tried it. After I made one, I kicked myself for not doing so years earlier. My students all liked them so much that we had to make them, which took class time, and the results were never quite as good as they could have been because I just don't have the heat treating facilities. I was really happy when a student came along who could take it over, and do it right, and with StewMac to handle the mail order end of it, I'm off the hook. Whew!

Alan Carruth / Luthier

[Bob Gramann]

I had to make a StewMac order so I added the scraper to it. It happened to arrive today just as I was ready to start scraping bindings. It's wonderful. I'm sure I'll find a reason to use my card scrapers again for something, but I love the new Carruth scraper and I heartily recommend it. I can scrape bindings with one hand holding the scraper and the other holding the guitar instead of having to hold the card scraper with two hands. It cuts beautifully. I look forward to my next carved top. Thank you, Al.

[David Schramm]

Since a hollow grind is like what we use on our ice hockey skates, couldn't you use one of those pocket sharpeners for figure skates and hockey skates to sharpen this scraper? It's called a Skate Mate http://www.skatemate.com

[Alan Carruth]

That Skate Mate thing looks like it would work well. Thanks for the heads-up.

Alan Carruth / Luthier

[Don Williams]

I have had one of Al's scrapers for a couple years at least, and I keep it in my shop apron at all times. It's the best scraper I've ever had, and worlds better than my Lie-Nielson card scrapers.

As to scraping vs sanding... In my humble opinion, and I think that of generations of fine woodworkers, I believe that they are NOT the same. Sanding is abrading, or tearing the surface fibers. Scraping is more akin to planing than sanding. Done right, and with a very sharp scraper, you can produce micro-fine shavings. Some compression can occur if you press too hard I suppose, but I don't tend to do that very much.

[Bill Brighton]

Those dermatome blades look a bit like disposable straight razor blades. There is a Japanese company called Feather that makes blades and razors (also surgical blades). Guys, these things are the sharpest things I have ever shaved with. They have several different kinds, pro-guard (with wire wrapped around it to protect you) professional, professional light and professional super. I have only ever gone as far as professional light because when I use that, I lose too much of my face. These are very reasonably priced, and for 24 dollars, you get a package of 20. You may get the same result, and even if they are not exactly the same, they are only about a dollar or so a piece.

http://www.classicshaving.com/Feather_Razors.html

Yeah, it's pretty good! And what do you think of cut throats?