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Thread: Al Carruth scraper - Sharpening

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    Default Al Carruth scraper - Sharpening

    I'm considering buying one of the Al Carruth scrapers from StewMac (the "Ultimate Scraper"). I notice that Al sharpens on a regular grinder with a fine wheel. I do not have a regular bench grinder. I have a Tormek Supergrind 2000. It works fine for all of my chisels, irons, etc. Does anyone know if that would work for the Ultimate Scraper? Thanks. -Mark

  2. #2
    Mandolin tragic Graham McDonald's Avatar
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    Default Re: Al Carruth scraper - Sharpening

    The idea of using the bench grinder is that it puts a burr on the edge. I use a fairly coarse grinding wheel to sharpen mine, set just a fraction past square so it grinds the shallowest of bevels on each side of the thin edge, though I think a finer wheel would be better. I suspect it needs the faster spinning wheel to get the burr, but the Tormek might work. If not a cheap bench grinder would be a worthwhile purchase even if you only used it for that one job. The Carruth scraper is a magic piece of kit and I rarely if ever use the old thinner ones any more.

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    Default Re: Al Carruth scraper - Sharpening

    StewMac sells their "ultimate mini grinder" as the optimal tool for sharpening Carruth scrapers. It uses 3" wheels. I've found that diameter just right for the purpose. You can get what's essentially the exact same grinder (3" wheels, variable speed) from Harbor Freight for about $40. It's billed as the 3" Multipurpose Bench Grinder, and also has a flex shaft if you have need for such. I bought one solely for sharpening Carruth scrapers. (Almost bought an ice skate sharpener to use on them, as it's pretty much the same principle.)

    A solidly fixed tool rest that's perpendicular to the wheel is critical for sharpening Carruth scrapers. My Tormek doesn't have that style of tool rest, and IMO the wheel diameter (at ~9") is too large for the task. Great for other things, but not for this.

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    Hands of Pot Metal
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    Default Re: Al Carruth scraper - Sharpening

    I was taught to use a coarse file to raise the burr and a large screwdriver shaft to turn it over. Long time ago from old guys. Worked fine on flat blades in Stanley #80, my scraper plane, flat scrapers and gooseneck scrapers. It’s a pretty basic skill, make shavings not dust.

    A grinder for a scraper seems overkill to me, kind of like a jig to sharpen twist drill bits.

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    Default Re: Al Carruth scraper - Sharpening

    Bill, that's how I sharpen all of my cabinet and gooseneck scrapers as well. (Although admittedly I've got a fancy burnishing rod that I got as a nice gift and replaced my screwdriver...).

    This particular scraper seems to be made of much, much thicker material, however. And I assume that's the reason it is advised that a power tool be brought in to the picture...

  6. #6

    Default Re: Al Carruth scraper - Sharpening

    Interesting idea, and I’ll have to try out the concept on an 1/8” or thicker milling spacer, but to paraphrase an obscene saying, anything’s a scraper if you’re brave enough! Although the Carruth video implies almost as much fussing as with a card scraper, if the edge lasts a lot longer, it’s worth it.
    By the way, it seemed to take many years for wood turners to realize that carbide (metal) milling inserts make really nice and inexpensive chisels/scrapers/gouges.
    (A skate sharpener normally has a wheel running in the same plane as the blade to do hollow grinding, so it’s really a machine tool, and does not leave the burr that Carruth says is doing the work. I made one of these back when I was skating alot and had a mill, but pretty tricky task anyway since figure blades taper over their length so you need to find the midline very accurately.)

  7. #7

    Default Re: Al Carruth scraper - Sharpening

    Ok, so I just blew my lunch hour - and then some, trying out variations of card scraper, low-temper tool steel, and really tough stuff. Soft pine, maple, apple. Ground crossways, lengthwise, fine, coarse. Not going to bore everyone, but the hardest (more than file hard) 1/8” material, a metal-cutting lathe blade, made a good scraper, held just enough off vertical to engage the edge. Did not matter how it was ground, including diamond lapped totally square. Probably would last the longest.
    My only traditional card scraper may not be the best - only have ever had one, with a good fresh burr, did work on everything, angled over a bit more.
    A normally sharpened hand-plane blade (i.e. 25 degree bevel) scraped the best, although it would probably dull fast.
    A bevelled blade from an antique Stanley scraper (the type that clamps through a hole in the center) worked fine too.
    No great conclusions except that the card scraper, since it comes in shapes, has no competition from things that don’t.

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    Default Re: Al Carruth scraper - Sharpening

    The Carruth scrapers are 3.5mm thick. Much closer to an ice skate blade than a card scraper, and they work on the same principle. The working edge is hollow-ground; It's not a "burr" as on a card scraper. Carruth may call it a burr, but it's a ground edge. The edges last a very long time if sharpened properly.

    As Graham said, with a little use they'll become your favorite scraper.

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    Registered User j. condino's Avatar
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    Default Re: Al Carruth scraper - Sharpening

    I have both of those scrapers from Stew Mac, but......

    To be honest I use a shop made set from a 3/16" thick chunk of scrap tool grade steel that cost me $4 just as often, if not more. I sharpen it in about 5 seconds on the belt sander and change the curves whenever necessary. 'Works fantastic.

    I think that a reground ice skate blade would actually work quite well. It is a lot more about the a sharp edge and skilled user than a fancy tool.....

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    Mandolin tragic Graham McDonald's Avatar
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    Default Re: Al Carruth scraper - Sharpening

    I don't think the Carruth scraper is a fancy tool. Just elegant in its simplicity. More power to ye if you want to fashion a piece of 3/16" steel into a scraper. I would rather spend a few dollars on someone to do that work and just use it.

    I resharpened mine today and thoroughly enjoyed a light finishing scrape on the inside of a maple back.

    Cheers

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  12. #11

    Default Re: Al Carruth scraper - Sharpening

    Quote Originally Posted by grandcanyonminstrel View Post
    I have both of those scrapers from Stew Mac, but......

    To be honest I use a shop made set from a 3/16" thick chunk of scrap tool grade steel that cost me $4 just as often, if not more. I sharpen it in about 5 seconds on the belt sander and change the curves whenever necessary. 'Works fantastic.

    I think that a reground ice skate blade would actually work quite well. It is a lot more about the a sharp edge and skilled user than a fancy tool.....
    From my tests yesterday, this is pretty much what I discovered. However even a very high quality figure skate blade (they’re much thicker than hockey ones) is not as hard as it or other alloys can get. The hollow grind is not related to cutting, but to edge control, and can be ignored for scraping. If the job was to scrape thousands of feet of board, then a specialty tool steel would be just the thing, but that’s not needed for us. The far softer card scraper can be very easily cut or ground to new shapes, which is a benefit for some things, like maybe furniture or moldings, and a thick piece of tool steel isn’t. So a broken (figure) skate blade, dressed with a couple swipes on a medium or fine belt, no mystery burr or hollow, can be useful for someone not attached to the time-consuming skill of turning burrs on cards. Not that I don’t enjoy arcane skills, but I’m also not trying to earn a living shaping wood.

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    Registered User j. condino's Avatar
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    Default Re: Al Carruth scraper - Sharpening

    Quote Originally Posted by Graham McDonald View Post
    I don't think the Carruth scraper is a fancy tool. Just elegant in its simplicity....
    At almost $100 delivered for the set of two for something you can make in fifteen minutes for $4 is definitely a fancy overpriced tool. They might as well sell them at Lie Nielson or Bridge City tools....

  15. #13

    Default Re: Al Carruth scraper - Sharpening

    Well, Lie-Nielson can sell you a $45 wallet to keep your scraper in! But seriously, selling specialty tools in very small quantities pretty much forces very high markup. Luthiers are a tiny fraction of even price-insensitive hobby woodworkers, so I’ve got sympathy for some of the ‘ridiculous’ pricing. I’m cheap in general, and tend to make my own jigs and such - a hobby in itself, but again, this takes time that I wouldn’t be able to afford if I were trying to get product out.
    I live close to NYC, in a fairly wealthy area, and sometimes find the ego-trip hand tools, often still unused, at tag sales for cheap, which is fun. I do like user-made and primitive tools, and collect them, since they often tell interesting stories of problem solving and making do.

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    Registered User tree's Avatar
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    Default Re: Al Carruth scraper - Sharpening

    My go-to reference on sharpening is Leonard Lee's excellent book, The Complete Guide To Sharpening. The chapter on scrapers is only 12 pages, but it covers the subject with clear and concise language, drawings and photos (NFI).

    It seems to me the important things about scrapers are 1) getting the geometry right, which is not at all difficult, 2) honing the edges to improve strength and sharpness, and 3) rolling the appropriate amount of hook on the edge for the purpose of the job at hand.
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    Default Re: Al Carruth scraper - Sharpening

    Quote Originally Posted by Jonathan Ward View Post
    ...As Graham said, with a little use they'll become your favorite scraper.
    I was anxious to try the Carruth scrapers but had not really used them until recently. I'm working outside of my own shop part of the time these days and we have the Carruth scrapers there. I learned to sharpen them and learned to use them. They were all we had for a while, but we got some card scrapers recently. To be honest, I prefer the card scrapers and I can't remember that last time I used the Carruth scraper. I've noticed that the other guys working there (less experienced than I) use the card scrapers most of the time too.
    As I see it, each type of scraper has it's place, and I've learned techniques that work for me with a card scraper, so perhaps that is why I prefer it.

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    Default Re: Al Carruth scraper - Sharpening

    "As I see it, each type of scraper has it's place,..."

    Roger that. In matters of taste, there is no argument. For each application there's a proper tool, and that decision can be very personal. If a man prefers to do his scraping with a soup spoon that he sharpens on a rock, more power to him. A couple of my favorite scrapers I made from old saw blades using a plasma cutter. Years back, Bob Beerman at the Bass Violin Shop in Greensboro showed me how he scrapes speed necks with a piece of broken glass. Works great for the purpose. I like the Carruth scrapers because they hold an edge for so long. More scraping, less sharpening. But they're not for everything.

    Back to putnamm's original question, everybody and his dog knows how to raise a burr on a card scraper. If you choose to buy Carruth scrapers, you will get the best results sharpening them using a 3" diameter fine grinding wheel with a solidly fixed tool rest at 90 degrees. If you choose not to buy Carruth scrapers, the matter is moot. As long as quality work gets done, everybody's happy.

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    Registered User sunburst's Avatar
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    Default Re: Al Carruth scraper - Sharpening

    Quote Originally Posted by Jonathan Ward View Post
    ...If you choose to buy Carruth scrapers, you will get the best results sharpening them using a 3" diameter fine grinding wheel with a solidly fixed tool rest at 90 degrees...
    Be aware that maintaining the straightness of the straight side of the scraper as you grind the edge is on you. One of the first things I had to do with a Carruth scraper at my place of work was to reestablish 'straight'. It had been ground to a slight inside curve, and scraping flat surfaces with it was impossible.

    (FWIW, we have to maintain 'straight' on card scrapers too, but we can do it relatively easily using a good straight file and sharpening stones. We can also flex the scraper in use so that we can scrape anything from a dead flat surface to a slight hollow. The flexibility of a card scraper adds versatility.)

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    Default Re: Al Carruth scraper - Sharpening

    Further beating on this expired equine: The whole concept that you can maintain a straight edge while cross-grinding by hand is simply flawed - at least at the level that might be relevant. You can’t really even establish a straight edge to any precision by honing against a stone unless the stone is freshly ground. I’ll bet that the concave edge you experienced is common. The adjustable convexity of the card version may indeed be much more useful on more parts of the instrument as you can eyeball the shavings and adjust the curve during use.
    But just for hogging a lot of wood quickly, a harder tool makes sense. So does a power tool.

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  23. #19

    Default Re: Al Carruth scraper - Sharpening

    I've been using them for a couple of years. I bought the large bean shaped one and then about a year ago I got the rectangular one and then the small one. I did buy the Stew Mac mini grinder. I love them. They hold an adge for a long time, they feel good in my hands and though I have card scrapers and was taught by my father years ago to sharpen them, I always reach for the Carruth scrapers. The large bean shaped scraper has a section that makes a great scraper for F5 recurves.

  24. #20

    Default Re: Al Carruth scraper - Sharpening

    I seldom comment,
    But an effective scraper is the easiest thing in the world to make, and sharpen.
    I have quite a variety of scrapers made of everything from spring steel shim stock, pieces of banding steel, old handsaws, disposable Japanese saw blades, and basically any steel that’s harder than cold rolled, but still soft enough That it can be cut with a file.
    I might use a belt sander to shape one, but I always sharpen with a file. As for what to use to burnish them with? It needs to be harder than the shaper you’re burnishing, and the smoother the better. A steel dowel pin 1/2” dia. By 3 “ long is an excellent choice. They’re case hardened, and very smooth.
    When I decide it’s time to resharpen the one in my hand I clamp it edge up in a vise and use the file lengthwise across the entire edge at once. It doesn’t take long, maybe 10 strokes. I use my fingernail to tell if I’ve rolled the edge over a bit. Next step, and most people won’t tell you this, but I’ve learned it from experience, is that I take fairly smooth stone and hold it flat against broad side of the scraper and remove any burr left from filing. Both sides. At this point you have pretty close to a perfectly sharp 90deg corner. Burnishing the prepared edge doesn’t take much effort, moderate pressure with your chosen tool held about 5-10 degrees from flat and one stroke in either direction on both edges is all it takes. Because it’s actually easy to roll the edge over too far, and the only way to test it is on the piece of wood you’re working on. It’s really quite simple once you’ve done it a few times, and only takes a couple of minutes.
    Now here’s my next trick, you can refresh the edge quite a few times by taking your burnishing tool and holding it flat against the broad side of the scraper flattening the burr and then re-burnishing it the normal way.
    I love my scrapers because I can remove a lot of material quickly, they won’t tear out figured grain, they can leave a very slick surface, they make less dust then sandpaper, and they can give you a bit of an upper body workout, and who doesn’t need that?
    Even if you don’t like all my ideas, try some of them. You might be surprised.

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