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Clarification on scraper sharpening

Discussion in 'MACHINE RESTORATION & WAY SCRAPING' started by toms73novass, Jan 19, 2017.

  1. toms73novass

    toms73novass United States Swarf Registered Member

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    I have read mutiple posts that the blade should be sharpened to a negative angle of 93-95 degrees.

    Could you please indicate should it be sharpened like A or B. I thoughts that it should be B.
     

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  2. Bob Korves

    Bob Korves H-M Supporter - Premium Content H-M Supporter-Premium

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    It should be A, negative rake.
     
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  3. easymike29

    easymike29 United States Active User Active Member

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    Drawing1.jpg
    Better yet...
     
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  4. Bob Korves

    Bob Korves H-M Supporter - Premium Content H-M Supporter-Premium

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    Yes, easymike29 shows the way most people do it, that way you have two edges to use before having to sharpen again...
     
  5. toms73novass

    toms73novass United States Swarf Registered Member

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    Thanks for the info, I'm sure I'll have more questions as I begin to experiment and learn.
     
    Last edited: Jan 20, 2017
  6. Bob Korves

    Bob Korves H-M Supporter - Premium Content H-M Supporter-Premium

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    I must say though, that I use a different angle, maybe 3-5 degrees (85-87 degrees from the handle) and notice that the drawing shows much more bevel than what 88 degrees would really look like. A scraper with an angle like the drawing would be difficult to make cut in use.
     
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  7. easymike29

    easymike29 United States Active User Active Member

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    The drawing is purposely not to scale to emphasize the orientation. I might add that the the entire bevel is ideally on a 12" radius.

    Gene
     
  8. Bob Korves

    Bob Korves H-M Supporter - Premium Content H-M Supporter-Premium

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    Yes, Gene, there should be a radius in the cutting edges of the tool as seen in plan view. The radius changes depending on the work being done, and to some extent on preference and how the tool is held. A larger radius for rough scraping large flat surfaces, smaller radii for finishing, dovetails, etc.
     
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  9. Inflight

    Inflight United States Active User Active Member

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    I just made a quick video showing how I sharpen a carbide tipped scraping tool.



    Let me know if you have any questions.




    Matt
     
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  10. Uglydog

    Uglydog United States Active User H-M Supporter-Premium

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    Please note that in addition to the rake the radius also matters.

    Additionally,
    HSS is easier to sharpen than Carbide, at least on the wheels that most of us have on our bench grinders.
    HSS hones also well.
    Carbide costs more to begin with, and while a sharp edge may last longer, that should not mean that you need carbide in order to produce great scrapes.
    My opinion based on reading and my Minnesota scraping mentors.

    Daryl
    MN
     
  11. Bob Korves

    Bob Korves H-M Supporter - Premium Content H-M Supporter-Premium

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    You can get a suitable carbide blanks for a few dollars or less if you look around, and braze or clamp them to a shop made handle. Honing the cutting edges by hand works fine, though Matt's setup is pretty elegant. The corners of the radius need to be intentionally dulled in both the vertical and horizontal planes so they do not dig and and gouge the work if the tool gets a bit off level.
     
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  12. Uglydog

    Uglydog United States Active User H-M Supporter-Premium

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    Bob Korves,
    You are likely correct.
    However, my emphasis is that it's ok to use HSS.
    It actually does work. And depending on your set-up it may be a better cheaper option.
    And yes, moving to carbide at some point is appropriate and good.
    But, we don't need to go nuts thinking and believing we must have carbide to begin our learning process.

    Daryl
    MN
     
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  13. Bob Korves

    Bob Korves H-M Supporter - Premium Content H-M Supporter-Premium

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    Absolutely, Daryl. At a get together last Sunday, Ulma Doctor (Mike Walton) made a scraping tool from a file in a few minutes on a ordinary bench grinder. That is not even HSS, it is carbon steel. It worked just fine, and we were scraping mild steel. It is still completely usable as a file. Hand scraping is pretty easy and cheap to get started with. Carbide will stay sharp longer and will cut harder materials, but it is not at all necessary for learning how to scrape. A year or two ago I did my first scraping with a scraper made from a file, also with Mike as my mentor. Mike has one made from a small file, for doing small and tight dovetails...

    We are conditioned by Madison Avenue, and often by our peers, to think that it takes the latest and most expensive equipment to do good work in our home shops. Nothing could be farther from the truth.
     
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  14. T Bredehoft

    T Bredehoft Active User H-M Supporter-Premium

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    Well said, Bob!
     
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  15. Bob Korves

    Bob Korves H-M Supporter - Premium Content H-M Supporter-Premium

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    Check out this link of Dapra pricing for scraping equipment (with thanks to Ulma Doctor):
    http://www.moglice.com/Dapra/BIAXPriceList.pdf
    and you will see why Daryl chimed in. Their prices are outrageous, and their equipment is nice, but not at all necessary. One of the best things about scraping is that it can be done on the cheap, using brains and time and effort rather than money and more money. I think there is enough of a simmering nascent market for someone in the US to give Dapra some real competition.
     
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  16. bfd

    bfd United States H-M Supporter - Premium Content H-M Supporter-Premium

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    ulmadr and bob korves well said. the only thing is the thousands of scrapers (carbide tipped ) at the lb naval shipyard. with the fixture they provided in the carbide room. all sharpened to a 5 degree angle as bob indicated as an apprentice we got to sharpen the scrapers. yes there was enough scrapers to allow 20 apprentices to sharpen 8 hours a day 5 days a week and still have more to do grunt work for the peons the fixture set the radius don't know what it was bill
     
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  17. ericc

    ericc United States Active User Active Member

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    Hi Bob. Do you have a picture of this tool and the approximate angles? I tried making a scraper out of a file, and it did not do well. Actually, it was more like I bought a file at an estate sale that had been repurposed into a scraper. When I sharpened it, it didn't work. It made a few crumbs, but not enough to be useful.
     
  18. Bob Korves

    Bob Korves H-M Supporter - Premium Content H-M Supporter-Premium

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    Well, Eric, it was not my file and I did not grind it. It belongs to Ulma Doctor on this site and he might be able to help you with photos and angles. It looked like the angles were about the same as a commercial scraper, actually just one side was sharpened quick and dirty for the demo. It is important to get a good edge and to not overheat the file, or it will lose its hardness. Lots of BIG new machines were scraped in efficiently and accurately entirely with carbon steel tools before HSS and carbide came into use and before grinding entered widespread use for fitting machine parts. I understand that some of those old boys (and currently working scraper hands) could and can make chips that have a thickness of several thousandths, with smoke coming off of them, all day long, every day, by hand, for an entire career...
     
    Last edited: Feb 17, 2017
  19. Bob Korves

    Bob Korves H-M Supporter - Premium Content H-M Supporter-Premium

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  20. Sblack

    Sblack Canada Active Member Active Member

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    Can you suggest a source for quality carbide blanks that don't cost a fortune? I am told that there is good and poor quality cabide but I don't know where to source the good stuff. I am planning on brazing them to a ho,der as you suggest.

    Thanks
     
  21. Bob Korves

    Bob Korves H-M Supporter - Premium Content H-M Supporter-Premium

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    All you need is a piece of micrograin carbide, say perhaps 1" wide, 3/8 to 1/2" long, and 2mm, 3/32", or even 1/8" (3mm) thick, C2 grade seems to hold up well and chips less. Different sizes and tip radii work with different types of work and also depend on user preference. Blanks are available from places like MSC, and purpose made Sandvik Coromant scraper blades are available on eBay, though the prices have really increased (just looked, !!!) in the last few years. Great deals are still out there, though, with some searching. It is not rocket science, but some guidelines should be followed to have a good initial experience... PM me if you want help in deciding on equipment. I am a rookie as well, but I do understand what works...
     
  22. Sblack

    Sblack Canada Active Member Active Member

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    Thanks for replying Bob. I have the information on the geometry from biax for both the radii and the rake angle. I just picked up a diamond sharpening setup (accu finish) at an auction. All I need to do is fab the blades out of cold roll and get some carbide blanks. The sandvik inserts appear to be $50 each and the biax ones are about the same. Are the blanks from msc of a comparable quality? Richard King has shown guys in his classes the difference between chinese carbide and the good stuff. I would like to avoid the frustration of using poor material without having to spend a fortune. Am I kidding myself thinking I can make my own blades with cabide from Msc? Any other sources that anyone can recommend? Thank you for your insight.
     
  23. Inflight

    Inflight United States Active User Active Member

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    MSC, KBC Tools, etc are fine for brazing your own scraper blades. I purchased a 10 pack of thick carbide square blanks from ebay for less than $10 with shipping. These measure roughly 3/16" thick and are about 7/8" square. This tool is used to scrape large flat areas.

    For smaller areas like dovetails, I use the KBC carbide or even a cheap brazed lathe tool mounted on a screwdriver shank.

    Scraper Carbide blank.jpg


    Matt
     
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  24. cathead

    cathead Active User Active Member

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    Looking good, Matt!
     
  25. Bob Korves

    Bob Korves H-M Supporter - Premium Content H-M Supporter-Premium

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    Hi Matt,
    I really liked your video on your scraper sharpening, and also the nice setup you made for your surface grinder. I am doing the same, and bought an inexpensive diamond flaring cup wheel direct from China, 100 mm OD, 32 thick, 20 bore, and 10 wide abrasive, 600 grit ($11.41 for the wheel and $0.71 for shipping!). This will only be used to sharpen/hone the blade at low speed, not to form it initially. I have a carbide grinder for doing that. My question is: did you have to open up the hole in the wheel to 1-1/4" for the wheel adapter? If so, I would be interested in the setup you used for that. It is a non-trivial setup challenge, at least for me so far, after thinking about it for a few days. I would like to be able to set it up based on the O.D. of the abrasive, not on the existing hole, which might well be off center. This is a cheap wheel, and I want to get the hole in the center as well as the mounting face parallel with the abrasive face. I messed around with several setup options using my 8" rotary table, but could not get anything robust enough to chance cutting it with a boring bar. I was using a piece of Delrin with a center hole that would press down on the angled walls and four toe clamps to push the Delrin plate down toward the table, and trying to block it radially with four short bolts and flat washers in t-nuts. The t-slots were over full and the whole setup was just not solid enough. I also do not want to tear up the abrasive with the mounting. I can work harder on that approach, but thought I would stand back and rethink the setup. I did not come up with any good ideas for using my lathe for this, the slots of my faceplate begin too far out radially on the plate (D1-4 mount.)

    I am not interested in a $100 setup to machine my $12 wheel...

    Anyone else want to chime in as well? This is what I bought:
    http://www.ebay.com/itm/100mm-Diamo...326645?hash=item3f6b4fb9b5:g:uOsAAOSwOyJX4KyP
    [​IMG]
     
    Last edited: Apr 13, 2017
  26. TakeDeadAim

    TakeDeadAim H-M Supporter - Premium Content H-M Supporter-Premium

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    I recently purchased some sandvick scraper blades off eBay for a few dollars each. You don't kneed 10 of them, I have the original 5 I was issued as an apprentice and they all remain serviceable. The crazy prices in the list posted above are not reflective of what a scraper needs or costs. I have a Sandvick blade holder that is nearly 40 years old and is all I ever used. The Biax is a horrible tool and produces a rough finish. Scraping like file work is meant to be precision work carried out in a workman like manner. It is not a surface grinder or milling machine. Small amounts of material are removed with care. Get a photo of the screw clamp blade holders and make one to fit the blades you can find.

    86 the file handle as the tool is designed to be pushed by the hip, not the hand. Make some large ended wood handles of several lengths and for less than $30 you have a scraper. No need for an ink roller, glue. Piece of suede to a wood block, served me fine for 35 years. Permatex bluing works just fine at a few bucks a tube.


    Sent from my iPhone using Tapatalk
     

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