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Scraper test

Discussion in 'Getting Started' started by john lucas, Mar 25, 2013.

  1. john lucas

    john lucas AAW Forum Expert

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    I had time while my glue is drying on other projects to run this test this morning. You may not be able to see the details as well once I shrunk all the photos but I'll be glad to send you the bigger ones if you want.
    Top row left to right, then bottom row left to right. Someday I'll learn to add type to these photos.
    This is a piece of yellow poplar that had a patch in it that doesn't want to cut clean. I had already turned about 10 of these so I knew how it turns. The first photo top left is a 3/8" thick 3/4" wide flat scraper ground with a negative rake at about 60 degree included angle and burr raised by a steel rod which I have found is the best burr for this scraper.
    The second photo is my 1/2" thick round scraper, same negative rake angle, burr off the CBN wheel, which again seems to be the best way for this scraper.
    3rd photo is a skew laying on it's side, included angle about 43 degrees, no burr.
    4th photo bottom left, the 3/4" flat scaper with burr held at a 45 degree shear scraping angle. You notice a definite improvement in the finish.
    5th photo was a freshly sharpened bowl gouge with a 40 degree grind. A better finish especially on the end grain.
    5th photo, a #4 Hunter tool. It's hard to see in the shrunk photo but it was a better finish still especially on the end grain.

    I hope to have time to read all the scraper articles I've been collecting and to regrind a scraper into the very sharp negative rake grind that Stewart Batty has on his tools to see if it makes a difference.
    As far as scrapers being used as the final tool for finishing I'm a little mixed on that. I do quite often because I turn fairly quickly and sometimes leave little tool marks and it's easier to use the shear scraper to clean these up. On smaller projects like boxes and quite often on my hand mirrors the cutting tool is the last finish and never touched by a scraper. The wood simply looks better if I can do it that way.

    I did not include my Easywoodtool scraper in this test because quite simply it does not cut as clean. It did at first but after just very little use it won't cut nearly as clean as my flat scaper with a fresh burr. And I do mean very little use, mayby one bowl and few quick cuts to show students how it works.
     

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  2. You are correct. Can you at least verbally rate each for us?

    I am not surprised about the Hunter tool. I have found that they yield very good finish cuts where other methods are falling a bit short.

    Regarding the gouge cut: dd you also try a 42 degree gouge, a 52.5 degree gouge, or other freshly sharpened grinds :D? Sorry, can't help getting that in.

    Mark
     
  3. john lucas

    john lucas AAW Forum Expert

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    I did use a gouge that had a 55 degree grind. It left a finish that wasn't far off the 45 degree grind.
     
  4. Bill Boehme

    Bill Boehme Administrator Staff Member

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    I agree with Mark about the size of the images. How about some 100% crops of small representative areas that show how the tools affected the surface.

    What software are you using? If it is GIMP, there may not be a text tool. If you are using Photoshop (even Elements) there is a tool for entering text. Another good editor is Paint Shop Pro.
     
  5. john lucas

    john lucas AAW Forum Expert

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    I tried to resize the images but since I threw away the original raw images these crops aren't as sharp as I would like. Been cropped considerably and hopefully you can tell something from them. Since we can only put 5 images per message I'll post 2 messages.
    On these 3 images there is very little difference in the finish quality. The skew used as a scraper has a slight improvement. It didn't have a burr while the other 2 did. The included angle of the skew is smaller at about 40 degrees.
     

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  6. john lucas

    john lucas AAW Forum Expert

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    Here are the photos of the flat shear scraper. Same scraper as the first photo but used at about a 45 degree angle. It is much improved. The next photo is a bowl gouge sharpened with a 45 degree grind. Very much improved. It's hard to tell in the photo but the Hunter #4 cutter made a cleaner cut especially in the end grain.
     

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  7. robo hippy

    robo hippy

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    John,
    I am guessing that the wood is poplar??? For sure, any scraper flat on the tool rest will leave a torn surface. You can get huge differences if you are doing a heavy stock removal roughing cut, or a very light scrape with a fresh edge. Of course, wood type will make a difference as well.

    For shear scrape cuts, I prefer an inside scraper (swept back on the left side), with a dropped handle, and a shear angle closer to 60+ degrees. That leaves a better surface. The higher the shear angle, the better the cut. With the swept back profile, as you cut, you can move down the length of the swept back edge so you get a fresh cutting surface for the entire cut.

    Wish I had camera and posting skills....

    robo hippy
     
  8. Thanks, John, for taking the time to go through a test like this and then try to convey the results over the web with photos. Most of us have enough of a challenge to learn the skills of turning let alone internet and photo prowess and all of the daily "standard" things that life throws at us.

    As far as edges, angles, and quality of cut: I think that if everyone took the time to compare, there would be surprises and revelations as to what actually yields the results we might want without a lot of sanding or using the "grit gouges". I always try to visualize the cutting edge itself in space, only a fraction of an inch behind the wood it cuts and without a shaft or handle. Isolate that edge like this, without a reference to anything else, and then you can imagine any way you want what can be connected to it to hold it or control it. It is this edge that is important to understanding tools, cutting, angles, surface quality, etc.

    Sharp tools are important. Rule #1 for cutting wood, of course.

    Shearing is better for finished surface, but if you are not yet at the finish, why would you care? You need to remove wood quickly and grossly, then worry about finished cuts. That is, unless you choose to practice finish cuts as you rough.

    Most importantly, experiment like John. Try different approaches and see what works, rather than following an axiom that might have originated from an intellectual concept and not a practical one.

    One more thing: Don't get lost or hung up in the details that are more for having fun with the advanced or more theoretical concepts in turning. It's great entertainment for some, but a waste of time and energy for others and can get one off the path. Know which group you fall into, Grasshopper. :D
     
  9. MichaelMouse

    MichaelMouse

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    Confirms that when the wood moves, rather than the tool, the results obtained are the same with the same edge presentation.

    Though I still prefer the broad sweep gouge, where the shaving flows up the flute rather than full U turning like the Hunter tool, there are places where you have to turn the edge at 90 degrees to the handle to get the best combination of pitch and skew. For this I have the termite.

    Yellow birch. Inside cut from rim down about 3/4 stages. http://i35.photobucket.com/albums/d160/GoodOnesGone/7-Surface-In.jpg
    Yellow birch. Outside cut. http://i35.photobucket.com/albums/d160/GoodOnesGone/6-Surface-Out.jpg

    Note these are the "pick up areas" of the grain which are most difficult to keep clean. You can see what you get with little skew in the first picture where the rim was quickly trued.
     
    Last edited: Apr 2, 2013
  10. john lucas

    john lucas AAW Forum Expert

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    MM There isn't a U shape flute to the Hunter tool. When used in the bevel rubbing cut the shavings are coming off the tool in the same orientation as your Broad gouge, rolling across the tip.
    see the first part of this video.
    https://www.youtube.com/watch?v=nfp2kvhH6Mo
     
  11. MichaelMouse

    MichaelMouse

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    Go ahead and pull the tool over some wood by hand and watch the shaving turn in the trough and twist out. Or, look at your video and watch it do the same. As I said, it's a gouge at 90 degrees to the handle, like the termite.

    Advantage to the gouge is that you can take off quite a bit without compromising the surface quality by varying shear and skew. Gross. http://i35.photobucket.com/albums/d160/GoodOnesGone/ShavingWide.jpg

    Or fine. http://i35.photobucket.com/albums/d160/GoodOnesGone/InsideTrim.jpg

    You can see the wide shear area pretty well here, but the final slice exit is leaving a pretty good surface, regardless.
    http://i35.photobucket.com/albums/d160/GoodOnesGone/Peeling-Outside.jpg
     
  12. robo hippy

    robo hippy

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    Well, the longer the shear cutting surface, the more curly Q the shavings will be. So, the Hunter tool has a concave surface, and you can get a little curl. MM's 'broad sweep' gouges have a much longer vertical/skewed surface/sweet spot, so more curly. Standard gouges have smaller sweet spots, so less curl. The Thompson Fluteless gouge has a fairly long sweet spot, and I get nice curly's from it. I can get them with a 'broad nose' scraper as well.

    robo hippy
     

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