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Thread: Sharpening Card Scrapers - Rob Cosman's Way

  1. #1

    Sharpening Card Scrapers - Rob Cosman's Way

    While reviewing different approaches in preparing card scrapers I found the method used by Rob Cosman to be the most involved. Basically he recommends flattening and polishing the 3 surfaces of each side, eventually using a 16000 grit Shapton stone. He also employs the Charlesworth ruler trick to flatten a small strip on the adjacent sides. He then creates a burr on each side of the edge in a more customary way. All other methods found were much less involved. Do you think Rob Cosman's approach unnecessary and too involved?

    Here's a link to the Rob Cosman video for those that haven't seen it.
    Last edited by Steve Mathews; 06-05-2024 at 8:27 PM.

  2. #2
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    Steve, I do not recall a video by Rob on sharpening scrapers, but will note that the use of the Ruler Trick was the idea of Chris Schwarz.

    A scraper can be sharpened with just a fine grinder, such as running the edge along a 180 grit CBN wheel. This works well with thick blades (1/8") ..





    However, with card scrpers, where one seeks the finest surface, there are a few givens: flatten and smooth all edges, draw out the edge, turn the hook (10-15 degrees). This is illustrated here: http://www.inthewoodshop.com/Woodwor...29Scraper.html

    Note that the Ruler Trick is not used here. Plus, I only use a 600 grit diamond stone for flattening and polishing.

    I use a 1/8" diameter carbide rod to turn the hook. Thinner is better, and carbide does not require lubrication.

    About a year ago I came across the Accu-Burr rod. this has pre-ground angles for turning the hook, and it does both sides of the card blade at the same time. My pictorial review also modified the handles: http://www.inthewoodshop.com/ToolRev...Burnisher.html



    In short, there are a few steps that can be removed from Rob's method without any deterioration to the finished surface. Without meaning to appear critical, Rob caters to beginners, and also dresses up his technique a little.

    Regards from Perth

    Derek
    Last edited by Derek Cohen; 06-05-2024 at 7:51 PM.

  3. #3
    Id look at more you tubes of other people. We flattened three sides. I think it was file first, then on a stone 3 sides then pull a burr with a burnisher and likely oil was used.

    I dont use them that often.

  4. #4
    You can put a rough but effective burr quickly on a card scraper with a file and sand out the resulting surface on cherry or maple with 150#. Stoning the edge and faces before turning a burr with a hard burnisher will give a finer result, sometimes good enough to finish depending on the job, and you can knock down and renew the burr multiple times before going back to the beginning. Use a light touch when burnishing and the resulting small burr will be less fragile.

    I wouldn't polish the edge that fine before burnishing but everyone has an opinion. Try a medium grit stone and see what works best for you.

  5. #5
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    Derek, i may well be wrong, but i always thought the ruler trick came from the late David Charlesworth . . . . .

    If i am wrong, Lord knows it would not be the first time . .. .

    Best, Patrick

  6. #6
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    Patrick, the RT indeed came from David Charlesworth. He developed this idea for plane blades. However, Chris Schwarz first applied this technique to sharpening card scrapers (not Rob Cosman). Actually, I am under correction, Chris was given this technique by Deneb Puchalsi (Lie Nielsen).



    Rob is a fine teacher and I admire him greatly. It is not a criticism when I say that he borrows techniques from others. As another example, he acknowledges this when he can remember. He does not recall that he uses a (yellow) tape trick to replace the #140 block plane rebate he used to use, and that he got this from me.

    Regards from Perth

    Derek

  7. #7
    It is a good idea to work through the ideal method to prep a card scraper as you are learning.
    Basically (practically) square edges, polished, with a slight burr.
    Try both methods of turning the burr (in one like the Cosman video) the burr is turned directly. In another, you first burr from the flat face toward and edge, then burr that burr back out.
    Which last is also a method to shape up a scraper as it dullss. So try that, too.

    After a while, you will evolve your own methods for efficient work in any given situation. Sometimes you need all the steps in the progression. Sometimes you can drop a few.

    Back in the 70's when i thought i was getting good with card scrapers, a guy who was part of a lineage/tradition that went back into the 18th c and only makes high end handmade OBF (Old brown furniture) was talking about a run of pie crust tables he was finishing the tops for. He mentioned scraping and i got into card scrapers and details and kind of rattled on. He looked at me for a bit and then said. "I just use a red devil paint scraper and file it". After a while he allowed "You have to make a good handle for it. The plastic is gives out and is no good" For a lot of stuff, quick efficient smoothing, a paint scraper works well. after that, there are a range of old handled scrapers, intended to be used with or without burrs, are effective. Card scrapers are for final finish, or shaped ones made for detailing. I find i tend to use Starrett scrapers the most. for flat work and near corners.

    PS: I did find out later that the OBF guy did use card scrapers at times, sometimes for details.

    smt
    Last edited by stephen thomas; 06-06-2024 at 9:03 AM.

  8. #8
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    For $40, that Veritas Variable Burnisher does a helluva job...

  9. #9
    Quote Originally Posted by stephen thomas View Post
    It is a good idea to work through the ideal method to prep a card scraper as you are learning.
    Basically (practically) square edges, polished, with a slight burr.
    Try both methods of turning the burr (in one like the Cosman video) the burr is turned directly. In another, you first burr from the flat face toward and edge, then burr that burr back out.
    Which last is also a method to shape up a scraper as it dullss. So try that, too.

    After a while, you will evolve your own methods for efficient work in any given situation. Sometimes you need all the steps in the progression. Sometimes you can drop a few.
    This is what I would advise as well, Though I use the second method of first drawing out the burr, then turning the hook.

  10. #10
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    You really must first draw out the burr. That's where the steel comes from. Without doing so, the burr is tiny.

    Regards from Perth

    Derek

  11. #11
    Quote Originally Posted by Derek Cohen View Post
    Patrick, the RT indeed came from David Charlesworth. He developed this idea for plane blades. However, Chris Schwarz first applied this technique to sharpening card scrapers (not Rob Cosman). Actually, I am under correction, Chris was given this technique by Deneb Puchalsi (Lie Nielsen).



    Rob is a fine teacher and I admire him greatly. It is not a criticism when I say that he borrows techniques from others. As another example, he acknowledges this when he can remember. He does not recall that he uses a (yellow) tape trick to replace the #140 block plane rebate he used to use, and that he got this from me.

    Regards from Perth

    Derek
    I do recall Rob giving credit for the yellow tape trick to someone else but not as much as the ruler trick mentioning David Charleworth. Most important is he doesn't take credit for it himself. Derek - Thanks for letting me know that this was originally your idea. I use it with pleasant success frequently. As for the ruler trick the basis for it seems the same whether it's applied to a plane blade or card scraper.

  12. #12
    I'm not a Cosman fan and do believe this method is overly complicated. A lot of what he says, I don't agree with. Probably more than any other major YT content creator focused on woodworking. But we're each entitled to our own opinions and methods. But give it a try, if you like. If it works for you, then it works. There's more than one way to do most things, and so long as you're happy with the results, that's all that matters.

  13. #13
    Quote Originally Posted by Jimmy Harris View Post
    I'm not a Cosman fan and do believe this method is overly complicated. A lot of what he says, I don't agree with. Probably more than any other major YT content creator focused on woodworking. But we're each entitled to our own opinions and methods. But give it a try, if you like. If it works for you, then it works. There's more than one way to do most things, and so long as you're happy with the results, that's all that matters.
    Wow, that would put him below of a lot of "just fell off the turnip truck" buffonnery.

  14. #14
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    Consistency - both in depth and sharpness - is in my experience, what makes scraping with a card scraper successful and enjoyable. Like a lot of things, if you don't have the muscle memory and intuition for the tool, then going through every one of the steps in a "cadillac" method with care is a good way to get to that consistent result. But if you've done it a hundred times, you get a feel for what works, when you need a complete rehoning of the edge, etc, and those steps look like all spare-no-details, instructions: overkill.

    My personal favorite example of this in my life is with welding. If I want a good weld, I need to self-consciously go through every imaginable joint prep, measure my piece and adjust the welder from a reference to the right welding parameters for the weight and type of steel I'm welding, and then be very careful about how I approach the weld, and it has to be a flat weld line, or maybe only a little uphill (never, ever downhill). My friend the professional metal worker and former professional welder does everything I do through careful following of a routine in about 2 seconds in his head and with casual use of a wire brush, twists a dial, and runs a perfect weld without much regard to position, etc. If there is something special about the metal involved, add a minute while he changes the wire or electrode, and maybe polarity of the welder. I'm a lousy welder who can get to passable with careful effort; he's an expert who can exceed my passable quality without even thinking about it. Card scrapers are a simpler version of the same thing, I suspect.
    Last edited by Steve Demuth; 06-06-2024 at 1:41 PM.

  15. #15
    Quote Originally Posted by Cameron Wood View Post
    Wow, that would put him below of a lot of "just fell off the turnip truck" buffonnery.
    Well, I don't watch many of the "Just fell off the turnip truck" variety channels. And I guess I should have qualified that statement with "of what I have seen" or something like that, because clearly I haven't watched all of YouTube. I'm just saying that of the content creators that I have seen multiple episodes of, and there are probably two dozen or so that fit into that category, he's the only one that I regularly disagree with. It's to the point where I typically avoid links to his channel unless he's proclaiming information I can't find elsewhere. I don't trust his motivations.

    But that's just me. I'm not trying to say I know more than him, he's a bad woodworker, he doesn't know what he's talking about, or anything like that. If you're a fan of his, I don't have any problem with that and won't hold it against you. Different strokes for different folks. And he seems like a nice enough guy. I'm just not a fan.

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