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Thread: Card scraper machine marks?

  1. #1
    Join Date
    Jun 2016
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    Card scraper machine marks?

    I just finished up a small box using Padauk with a Spanish cedar bottom. I used hand tools for everything except for rough cuts. On the sides and top, I used a card scraper to get rid of some tear out. On the top around some tough grain, there is what almost looks like planer marks (third photo). I had just put a new edge on the card scraper. It's no big deal, but I'm just wondering if there is a better technique when using card scrapers. By the way, 3 coats of clear shellac followed by a steel wool and wax polish.

    pad_box_1.jpgpad_box_2.jpgpad_box_3.jpg

  2. #2
    Join Date
    Dec 2015
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    Quote Originally Posted by Bill McDougal View Post
    I just finished up a small box using Padauk with a Spanish cedar bottom. I used hand tools for everything except for rough cuts. On the sides and top, I used a card scraper to get rid of some tear out. On the top around some tough grain, there is what almost looks like planer marks (third photo). I had just put a new edge on the card scraper. It's no big deal, but I'm just wondering if there is a better technique when using card scrapers. By the way, 3 coats of clear shellac followed by a steel wool and wax polish.
    What exactly does "put a new edge on the card scarper" mean? Clearly the cutting edge of the scraper had some chips/defects, so now the question is "why"?

    Some possible causes include:
    • Edge not sufficiently stoned, or not sufficiently smooth off the file if you're one of those freaks who skips stoning. Check the edge with your fingernail before burnishing - it should be smooth and sharp like an edge you'd put on a smoothing plane.
    • Damage from burnishing. If you burnisher is too soft or nicked then it can hose the edge. Check the edge with your fingernail after burnishing - it should still be smooth and sharp like an edge you'd put on a smoothing plane.
    • Case-hardened steel from a previous burnishing not removed by filing/stoning. Steel gets harder and more prone to fracturing/chipping as you work it. After some number of burnishings (where that number depends on your skill and your tolerance for chipping) you have to file away the previously burnished steel and start from fresh metal. If you wait to long to do this or do an incomplete job of it, then the edge will "crumble" during burnishing. This is really a second sub-case of "damage from burnishing", but with a different root cause.

  3. #3
    Join Date
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    If it were me, if you felt those ridges, I would have worked them along their length. Not sure that the scraper edge will cause that problem. I think more likely is the scraper is following hard and soft areas of grain. Since a card scraper does not have a sole, you can fall prey to this pretty easily. If it was poor edge prep, I think you would see that show up by either not cutting, or leaving scratches along the length of travel, but not with those undulating ridges like you are seeing.

  4. #4
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    Looks to me like you were getting some chatter while scraping. Next time, try taking a less aggressive cut when you hear or feel the chatter. The only way to fix it is to skew the scraper across the chatter lines and take light passes.

  5. #5
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    Jun 2016
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    Cleveland, OH
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    Derek,

    Since this is only the second time I have put a new "hook" onto a scraper, I think you are probably on to something! I have a Veritas burnisher (the clam shell type, not the rod). I draw filed the edge, then ran the edge over coarse, fine and extra fine diamond plates. Then, used the Veritas burnisher. I did not do the finger nail test and I'll try that on my next go. It was taking curly savings at first, then got harder to use and was producing more saw dust than shavings. So, looks like a case of a dull tool and a lazy sharpener - me. Chalk it up to a learning.

    Thanks for the quick reply.

  6. #6
    Join Date
    Jun 2016
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    Cleveland, OH
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    Dan and Pete,

    Like you say, I was probably too aggressive with a dulling tool and started "riding the waves". I like the skewing idea and that makes a lot sense. Is it ever advisable to scrape across the grain?

  7. #7
    Join Date
    Jul 2015
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    Broadview Heights, OH
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    711
    Bill,

    The wood doesn't care. If that smooths out the surface, have at it. I often plane across the grain if that produces the surface I need.

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