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Thread: Cosman Kerf X-10

  1. #1
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    Cosman Kerf X-10

    Has anyone tried this kerf-finishing tool for half-blind dovetails? Is it worth buying?

    Once again, Rob has mesmerized us with a dazzling demonstration of its use to punch out the remaining triangle of the kerf after sawing (at an angle) around the pins. It leaves a kerf straight down, all the way to the gauge line. To see it in action, start at 26:23 in this video:

    https://www.youtube.com/watch?v=sx0tc-UGRXY&t=1646s

    Here's the listing of the tool:

    https://robcosman.com/collections/sa...mans-kerf-x-10



    Expensive? Absolutely. Gimmick or useful? That's my question. Seems like it would simplify chiseling because you'd only need to pare out the end lap. Anyway he sure makes it look easy.

    I can't believe I'm considering spending this much money for a tool like this.

    I'll bet there are some here who know of a simple, inexpensive alternative to the fancy Kerf X-10. Or let's hear from the purists who only chisel at this step. Or maybe we'll see a testimonial for the X-10. Curious to hear.

  2. #2
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    Oct 2019
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    I know the alternative, a
    0,5mm card scraper will do the job nicely. I started using one recently with a light mallet. Maybe I will make a folded back for it.

  3. #3
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    Quote Originally Posted by Bob Jones 5443 View Post
    Has anyone tried this kerf-finishing tool for half-blind dovetails? ...
    Something like that has been discussed many times, at least, over the last few years. Derek Cohen was the first to write about it that I noticed. He built one himself, and I'm sure has described it on his website if you can't find the description here. Taylor Toolworks had one that looks just like your picture under their TayTools brand. And as I recall several others have had solutions that serve the same purpose but with a different form factor, a card scraper corner being the least dedicated.
    Last edited by David Bassett; 01-02-2021 at 4:28 AM. Reason: typo

  4. #4
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    I may have answered my own question (while not reading the replies above!). I went out to the shop and found an old scraper that is exactly 0.025". Rob's fancy product is 0.025", he says, to make sure that there are no shelves left in the kerf after sawing on the diagonal with the dovetail saw, which has a 0.024" kerf.

    Wouldn't you know, the scraper pounded right into the kerf. It's nowhere near as elegant as the brass-backed special tool with the mahogany handle, but it was basically free. I think I'm going to work it into my kit.

    It looks like the Tay Tools part is "currently unavailable."
    Last edited by Bob Jones 5443; 01-02-2021 at 5:18 AM.

  5. #5
    Hello Bob,

    I also was very intrigued last year concerning this tool and decided to make my own. I used the extras from a saw I had made so had the bit kicking around the shop. It's not the prettiest tool around, but works well.

    One tip I've learned is to be sure to put a clamp across the dovetails with light pressure. You don't want the 1/2 pins cracking. Happened to me once before I started to use the clamps. This will depend on the species of wood as well as the thickness of the 1/2 pins.

    Michael

    20191002_122106.jpg

  6. #6
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    I purchased one from Ron Bontz a few years back. Beautiful tool. Works great. I agree with Michael that for a little extra peace of mind, clamp across the dovetails.
    Last edited by Phil Mueller; 01-02-2021 at 9:18 PM.

  7. #7
    Amen. I noticed Frank Klaus doing this several years ago.

  8. #8
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    Ron Bonz's Kerf Maker is a great help with half blind dovetails.

    Kerf Maker.jpg

    Before this my home brewed tool for this was a piece of broken saw blade also used as a scraper.

    Not sure but one of the master woodworkers, may have been Frank Klaus (see note), used a piece of bandsaw blade with the teeth filed off. (Derek Cohen mentions Tage Frid for his first time seeing this done)

    jtk
    Last edited by Jim Koepke; 01-02-2021 at 3:28 PM.
    "A pessimist sees the difficulty in every opportunity; an optimist sees the opportunity in every difficulty."
    - Sir Winston Churchill (1874-1965)

  9. #9
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    The first time I saw this was Tage Frid using a piece of bandsaw blade, about 20 years ago.

    I can say, with some confidence, that I made the first dedicated kerfing tool. This was in 2011 - certainly long before Cosman ...

    http://www.inthewoodshop.com/ShopMad...erfChisel.html



    Regards from Perth

    Derek

  10. #10
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    Iíve used a .024 card scraper from Lee Valley for years. A few taps with a tack hammer and it works perfectly. Six bucks and easily replaceable if necessary.

  11. #11
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    Hi all and happy new year.
    With respect to my little dovetail tool. I use 1095 spring steel, same as my saws, so the steel is not as brittle as a chisel. Mine can be tapped from two different directions. The top of the brass back or from the back of the handle. Wooden mallet preferred. Depending on your work position. They can be made with or without reverse teeth, no set of course, and are available in 3 thicknesses. 0.015", 0.020", and 0.025". The available wood species are several with a batch of resin infused curly maple slated to be turned in the next couple of months. I ran out of stabilized quilted/curly maple. Sorry. Otherwise, the card scraper works fine. As others have said, the method has been around for some time. Best wishes,
    Ron

  12. #12
    I have been looking at this tool recently and decided to make my own out of an old cheap big box store hand saw.

    Anyway, how much of a variance can there be between the thickness of the kerf extender and my dovetail saw plate + set ? just For reference I have a Veritas Dovetail saw which comes in at .026 including the set. Should the kerfing tool be the same thickness as the kerf left from my saw, or should it be slightly larger?

  13. #13
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    Quote Originally Posted by Ethan Lorden View Post
    I have been looking at this tool recently and decided to make my own out of an old cheap big box store hand saw.

    Anyway, how much of a variance can there be between the thickness of the kerf extender and my dovetail saw plate + set ? just For reference I have a Veritas Dovetail saw which comes in at .026 including the set. Should the kerfing tool be the same thickness as the kerf left from my saw, or should it be slightly larger?
    My understanding is it should be the same size as the saw plate. It could likely be a bit thinner. If it were much thicker, it might be more likely to cause splitting.

    jtk
    "A pessimist sees the difficulty in every opportunity; an optimist sees the opportunity in every difficulty."
    - Sir Winston Churchill (1874-1965)

  14. #14
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    Red Devil...UNION, N.J. USA No.4101



    Rosewood and brass in the handle, very stiff blade....Bought mine for a dollar bill....just a simple "putty knife" nothing fancy...except..it is the same thickness as the saw's kerf.

    Just used it last building some drawers....

  15. #15
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    Derek, on the basis that woodworking has been about rather a long time it's a strong comment to say you made the first dovetail kerfing tool. All manner of shop made devices have never been recorded.
    Props for publishing your useful method before Cosman.

    In regards to how useful it is, I don't know. Perhaps I'll need to try it some day and report back. If someone wants to drop their own money on any kerfing tool, go right ahead.

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