Large scraper use....

Discussion in 'Newbie' started by Marc Phillips, May 17, 2009.

  1. Marc Phillips

    Marc Phillips

    Joined:
    May 17, 2004
    Messages:
    5
    Location:
    Columbus, GA
    Home Page:
    I have one of those large heavy scrapers... 1 1/2" I think...

    I remember using it once quite a while ago and loved the way it cleaned up the transition area of the bowl I was working on and made it very easy to get a nice curve there... Normally I do the whole bowl with a 1/2" bowl gouge with a fingernail grind.

    Anyway, I was working on a Sweetgum green (sorta) bowl yesterday and thought "that scraper would work great on this transition curve" and sharpened it up....

    .... and all it wanted to do was catch... and catch... and catch... changed the tool rest height, tried changing the angle of attack... catch, catch, catch.... had the Oneway curved tool rest very close to the wood... more catches....

    Went back the bowl gouge laid over on it's side and finished scraping/light cutting that area and finished the bowl...

    So... what was up with that? The last time I used that heavy gouge I had beautiful ribbons coming off of it, almost no effort at all as it glided across the surface... now I can't get it to work at all. :mad:

    Any help?
     
  2. Bill Boehme

    Bill Boehme Administrator Staff Member

    Joined:
    Jan 27, 2005
    Messages:
    8,120
    Location:
    Dalworthington Gardens, TX
    Home Page:
    If you are working on the inside of the bowl, make sure that the tool rest height is adjusted so that the edge of the scraper is ABOVE the center line. Also hold the scraper so that it is tilted slightly downward (i.e., the back of the handle is higher than the cutting edge). When you use the tool this way, the wood is moving away from the tool so a dig-in is far less likely. When you are scraping, make sure that the tool is held solidly on the rest and you use the left hand edge of the scraper only. A big fat scraper like that is sometimes a bit tough to handle inside of a bowl. I prefer to rotate the scraper about 45 degrees CCW to shear scrape, but you should master the basic method first.

    On the outside of the bowl, the scraping edge needs to be BELOW the center line in order to keep the wood moving away from the edge.

    Finally, make certain that you are not pushing the tool into the wood -- it should touch the wood very gently -- if you find it necessary to push the tool into the wood to make it cut, then the tool is dull. Depending on how dull it is, you may only need to pull another bur or you may need to touch it up on the grinder and then raise a bur -- some turners are satisfied with the edge as it comes off the grinder, but it is not very durable.
     
  3. odie

    odie

    Joined:
    Dec 22, 2006
    Messages:
    4,420
    Location:
    Deep in the woods

    boehme......

    By "pull another bur", do you mean by burnishing the edge?

    I have one of the carbide tools.......I think it may have been made by Oneway, that has a carbide post intended for burnishing a burr on a scraper. I haven't used this for many years because I've never been very successful with it. I've concluded that it would probably do a much better job on carbon steel, but it never really satisfied my needs for a good burr on HSS.

    Then again, you may be doing things entirely different than I've experimented with in the past.........and, I guess that's what I'm enquiring about.....

    I'm one that has been satisfied with the burr straight off the grinder. I think you're right that it doesn't last as long as I'd like for it to.......but, it's not much of a consideration for me, because I can get a scraper sharpened and back on the lathe in about 10 seconds.


    ooc
     
  4. Bill Boehme

    Bill Boehme Administrator Staff Member

    Joined:
    Jan 27, 2005
    Messages:
    8,120
    Location:
    Dalworthington Gardens, TX
    Home Page:
    Odie,

    It is essentially the same way that a bur is pulled on a cabinet scraper and as described in a recent article on sharpening scrapers by Alan Lacer in American Woodturner. I think that I was like a lot of people and did not use quite the right technique when pulling a bur with a burnishing rod, but I recently had a class with Alan Lacer and he showed how it is done. The problem that I was having was being caused by applying too much pressure on the edge of the scraper. The actual amount of pressure needed is rather light because too much pressure will roll the edge into a curl which will not cut anything. It is hard to describe in words how much pressure to apply, but it would be something in the neighborhood of a firm handshake and far short of a white knuckle grip. A single pass is made with the burnisher and the angle is a few degrees from perpendicular to the top surface -- essentially the same as the little burnishing jig that you have -- I think that I have one that is just like it -- made by Veritas. According to Alan who made a bunch of photomicrographs of scraper edges sharpened with different techniques, the quality and durability of the pulled bur is far better than the rough crumbly bur that comes off the grinding wheel. Alan uses a diamond hone to remove that bur before pulling one with the burnishing tool.
     
  5. Jock Manuka

    Jock Manuka

    Joined:
    Oct 8, 2008
    Messages:
    23
    Location:
    Te WahiPounamu

    yep , thats the one , Scraper blade down Elbow up .
    Get yourself a rough platter blank , and turn a plate from start to finish .
    Worked for me :)
     
  6. MichaelMouse

    MichaelMouse

    Joined:
    May 16, 2005
    Messages:
    3,540
    Your difficulties sound familiar. It is for the reasons you state that I don't use scrapers. I haven't the skill required to touch and follow a surface properly without risking a grab. That's why I use a gouge to do that job, where I get a bevel to lay on the surface and keep track of the bite I'm taking. Not as sensitive to out-of round conditions once you start it, too. And if the picture of the spalted bowl you posted on WC is the bowl in question, it is much less likely to peck out punk as well.

    A scraper can be "sharpened" many ways, with each giving you a bit different angle to worry about. Read a bit about cabinet scrapers on the flat side, and you'll learn more about how to cut with burrs, and how to make large, small or not at all work for you. It's a firm hold on theory rather than rules of thumb that will get you there. How far you roll them determines what presentation gives you the best sharpness angle. Essence of no-bevel work is an infinite relief angle. I love my Veritas dial-a-burr for my cabinet scraper. With variable burnishing angles I can get the degree of aggressiveness I want and the durability and angle required to even scrape dried squeeze-out.
     

Share This Page