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Thread: Scraper Questions

  1. #16
    Join Date
    Feb 2008
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    E TN, near Knoxville
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    Quote Originally Posted by JohnC Lucas View Post
    One other advantage of the negative rake scraper is it applies almost no force against the wood so you get less chatter than you do with a regular scraper. This is especially true on thin platters with wings such as natural edge bowls. I used to think that holding a scraper handle up high was the same thing as a negative rake scraper if they both had the same included angle to the edge. It's not. My older tear drop scrapers were ground about 75 degrees. So flipping them over does produce a negative rake but it still works like holding a handle high on a regular scraper. Sharpening a scraper to a more acute angle like 45 degrees and giving it a negative rake on top is a much more controllable tool and leaves a fantastic finish.
    I think holding the handle high is equivalent to the NRS in the geometry of the edge relative to the wood (if the included angle of the tool is identical) but not in the presentation and the amount of control you get by holding the tool horizontal and flat against the rest. With the handle high and the edge down it seems the wood would more easily deflect the tool downwards and not make as even a surface.

    Funny thing about these scrapers today - yesterday I read from a woodturning book written by F.Pain in 1957. The guy showed how he ground curved edge scrapers with profiles that look very much "Rudy Lopez's" grind - Pain ground them from old files with a sloped top similar to negative rake scrapers but he doesn't call them that. He said they worked better with this grind but didn't attribute it to the grind angle but to the idea that he was grinding down into softer steel in the middle of the file. He raised a burr with a hardened rod.

    Another thing he recommended 61 years ago - "Small flexible hand card scrapers shaped with a curved end are extremely useful for troublesome places." Hey, I like that idea.

    JKJ

  2. #17
    Best explanation for why a standard scraper doesn't work like a NRS, and it seems to make sense, is when you hold the handle high like that you get a 'trailing cut', which would be like taking a card scraper and tipping it to 45 degrees or so instead of say maybe 80 degrees. The burr is turned too far over and works more like a rake than a cutting edge. I have applied that thought to my shear scraping too. So you start by rubbing the bevel without it cutting, and then roll it slightly past the bevel rubbing cut. It does seem to cut more cleanly.

    Tool steel..... that could mean a lot of things... I did find out with the bimetal blades from Lennox that the teeth are M42 HSS.... Maybe we should find out if the M42 is available in 1/8 inch thickness.... Think the guy in the video was using that scraper on some rosewood....

    robo hippy

  3. #18
    Join Date
    Oct 2008
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    Quote Originally Posted by John K Jordan View Post
    Kyle, I read your post again, and I think I misunderstood the first time - I thought you might be trying to cut what would otherwise be the bottom surface and the obtuse angle on the ground bevel.

    JKJ
    Thanks for the info! I was cutting with the top sharp surface, although handle level and "upside down". Did try sheer also, not working well..... Just trying to find a "cheap" alternative to regrinding and repurposing a high dollar scraper...... I use my skews as NRS.

    Oh, I remember your cabinet scraper post from a while ago, and I've been using them. Not on the lathe though. I do know they cut skin much faster than wood...... DAMHIKT.

  4. #19
    Join Date
    Mar 2007
    Location
    Wetter Washington
    Posts
    857
    Sharpening scrapers "up-side down", Dave (D-Way tools) and Jimmy Allen (Boxmaster Tools) are both big fans of sharpening scrappers upside down.
    Besides conventional scrapers Dave has negative rake ones, largely due to Jimmy and another local (Scott) encouraging him
    Jimmy's tools are (I think) exclusively NRS.
    (for those not in the Seattle are, Jimmy is well known for his box work. Dave encouraged Jimmy to develop his own tools to do boxes with, so he did. The "plan" is for Dave and Jimmy to have adjoining booths at the Oregon Symposium)
    Making sawdust mostly, sometimes I get something else, but that is more by accident then design.

  5. #20
    Oh no!!! Not more tools..... If Jimmy wants to demo box turning, he is welcome to play on the lathe in my booth.... I do have a bunch of dried box blanks...

    robo hippy

  6. #21
    Join Date
    Feb 2018
    Location
    Sparta Tn
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    122
    I wish i could be a that symposium. I just checked and didn't win the lottery so guess I'll stay on this side of the Mississippi for a while.
    Last edited by John K Jordan; Yesterday at 4:24 PM.

  7. #22
    I should have been more explicit - my post was in reference to that of John Lucas.

    Left click my name for homepage link.

  8. #23
    Join Date
    Feb 2008
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    E TN, near Knoxville
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    Quote Originally Posted by John Keeton View Post
    I should have been more explicit - my post was in reference to that of John Lucas.
    Ok, nevermind, then! The handy "qoute" feature can minimize ambiguity.

    BTW, I didn't make it to the Knoxville club meeting last week so Ii don't know what tilted/offset platters were shown. The May newsletter should be out soon, I think.

    JKJ

  9. #24
    Join Date
    Feb 2008
    Location
    E TN, near Knoxville
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    Quote Originally Posted by Reed Gray View Post
    ... I would be willing to bet that a carbide burnisher would turn a burr on it...
    Reed, I tried using a carbide burnishing rod on one of the 1/8" thick StewMac scrapers a few minutes ago. It certainly did raise a burr, even with light pressure. That's not surprising since it does with 10v steel.

    I'm running on 10% today and wasn't able to test it on wood but I'll try to in a few days. Perhaps using them with a burnished burr would work better for woodturners than luthiers. Or at least get extended use from them with each sharpening.

    JKJ

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