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Thread: Shear Scraping

  1. #16
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    Quote Originally Posted by Robert Willing View Post
    ...What is the right angle to sharpen a shear scraper? Do I need a burr? I can't wait on a video too old for all this nonsense. I have watched two videos With Out/info. What ever happened to the shear scraping with carbide cutters. I know of two a) a shear carbide cutter and b) a square carbide cutter with a radius held at an angle. No sharpening involved. Do these shear scraper only work on end grain?
    Robert, sorry. In my personal experience there is no clear answer to some questions. No formula that fits all. Others may have different opinions.

    What is the right angle? "Sharp." A burr? Maybe, maybe not. Carbide? Maybe, probably not.

    I should say that I don't use normal scrapers for shear scraping. I prefer gouges instead so some of the following, such as the burr and angles, may not apply.

    The precise angle doesn't seem to matter as much as the edge being sharp. For example, I have shear-scraped with extremely small angles on the wings of a gouge and also on less extremely small angles, both with good results. I say "sharp" because that, to me, is more important than the angle. I like to shear scrape the outside of a bowl with a the wings of a spindle gouge. I sharpen with a 1200 grit CBN wheel on a Tormek (I used to use the Tormek stone water wheel). After I sharpen it I hone, strop, or polish the grinding burr away. When ready, the gouge is sharp enough to shave with (I sometimes test it on the hair my arm, just like a knife or skew chisel). Some people leave the grinder burr on a gouge and that works too, however, I believe a grinder burr is fragile and is knocked off fairly quickly against the wood. For me, a honed edge works better and longer.

    The other John Jordan uses and sells a shear scraper that looks kind of like a wide skew chisel with a bevel on one side only. This is used extremely sharp and with no burr - the grinding burr is probably best removed with a fine ceramic hone. This works very well on the outside of his hollow forms and works well for bowls and things as well.

    I think the more important thing than the angle of the grind is the way the tool is presented, with a gouge for example, how it is rotated along the axis of the shaft and how it is angled relative to, say, the top of the tool rest. What I do is start with a razor sharp tool the apply it to the wood and see what it does. If it doesn't make whisper thin, almost transparent shavings, I try a different presentation, different speed, different pressure, different tool. I find that some things work better for some woods and circumstances. It may seem like voodoo magic but that's the way I work. A simple formula is a good starting place but doesn't always do the best job (for me).

    The tool needs to be sharp. In my experience that leaves out most carbide cutters, especially inexpensive industrial cutters with flat upper faces. They are just not sharp enough (to suit me) and when they get dull they are difficult to sharpen. With end grain they can tear out grain far more than a sharp steel edge. And any tearout can be difficult to remove by sanding. I once bought a set of the Easy Wood tools and was so horrified by the surfaces I got compared to a gouge that I sold them. I have no experience using them as as shear scrapers. If they remove whisper-thin shavings and leave the surface smooth and with no tearout then use them.

    On a good day with good wood a nicely shear scraped surface needs very little sanding - I do little power sanding, often sanding mostly by hand starting with 220 or 320 paper, even finer grit for small turnings in hard wood.

    For a convex surface (e.g., the outside of a bowl), a shear scraping edge is probably best with a fairly straight edge - this smooths out small imperfections in the wood. For a concave surface (e.g. the inside of a bowl) a shear scraper is best with a shallow curve, a little more curved than the wood. For the inside I usually use the rounded or tear drop shaped flat HSS scrapers such as what Sorby sells. When very sharp and held at a shearing angle, they can take off the whisper shavings that give a smooth surface. With these I do occasionally use a burr on the steel cutter, depending on how well it is working. When I use a burr it is usually pretty small and raised with a carbide burnisher, not from the grinder.

    If this seems confusing with options, that's because it is. If new to shear scraping I would recommend starting with this: sharpen a bowl or large spindle gouge with long swept-back wings, hold the tool against the tool rest with the tool held at about a 45 degree angle to the right (or left, depending on the curve of the piece), rotate the tool until the lower swept back wing can be touched lightly to the wood (the flute will be "up" and/or rotated a bit towards the wood, perhaps even with the upper wing almost touching the wood for a deep-fluted bowl gouge). Touch the lower edge very lightly to the spinning wood and slide the tool to the left (or right - in the direction the flute is facing) and adjust the angles, pressure, and speed of motion to get very fine, thin shavings. This can be demonstrated in 10 seconds but is hard to explain in words!

    I suggest trying many variations and different tools and discover what works best for you, and more importantly, what kind of surface you are satisfied with.

    When I'm shaping a bowl or form I often do what as some others I know do - while shaping the piece and long before I get to the final shape I make lots of "finish" cuts then cut them away and repeat. I might try different lathe speeds, different tools, different body motions. A bit of each of these "finish" cuts can be shear scraped to experiment and discover what works best for that wood and that shape. Since I've done lots of finish cuts when approaching the final shape, when I finally get to the Final finish cut my hand and arms and stance are well-practiced and I've decided the best tool and method of shear scraping for that piece. Note that I'll never win a turning speed contest.

    Videos may be ok for learning some ways to go about this. Live demos are great. But there is nothing better than spending some time with an experienced turner. Turning clubs are perfect for meeting and arranging personal one-on-one time.

    EDIT: I forgot something likely important which almost everyone forgets to mention when they say what works for them - I mostly turn dry wood, cherry, dogwood, walnut, maple, ebony, olive, cocobolo, etc. The way I shear scrape works well for me with dry wood so I use the same thing for green wood. Something else may work as well or better for someone else when turning wet wood. I also do a lot of spindle turning and don't find much use for shear scraping there.

    JKJ
    Last edited by John K Jordan; 11-16-2017 at 12:28 AM. Reason: Forgot something important

  2. #17
    Quote Originally Posted by Robert Willing View Post
    ?... What is the right angle to sharpen a shear scraper? Do I need a burr? I can't wait on a video too old for all this nonsense. I have watched two videos With Out/info. What ever happened to the shear scraping with carbide cutters. I know of two a) a shear carbide cutter and b) a square carbide cutter with a radius held at an angle. No sharpening involved. Do these shear scraper only work on end grain?
    Here is what I do. First, I consider shear scraping a technique and not a tool so my shear scraping is done with a bowl gouge on exterior convex surfaces and with a regular half round scraper on interior surfaces.

    When using the bowl gouge, I drop the handle roughly 45 and tilted in a pull cut about 45. The tool is rolled over until the flute is almost closed, but the upper wing is about ⅛" from touching the wood. The Ellsworth grind and similar swept back grinds are good for this type of shear scraping. You really ought to get David Ellsworth's video to see how it's done. On the interior I use the scraper the way that Reed does ... rolled over on its left corner about 45. The bevel angle isn't important because it's not a bevel rubbing cut. I prefer removing the grinder bur and pulling a bur with a burnishing tool.
    Bill

  3. #18
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    Thanks for the response JKJ and Bill I and going to read these a couple times to make sure I understand all this good info I do suspect the type of wood has a lot to do with the results.

  4. #19
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    Quote Originally Posted by Robert Willing View Post
    Thanks for the response JKJ and Bill I and going to read these a couple times to make sure I understand all this good info I do suspect the type of wood has a lot to do with the results.
    Be sure ask if anything is confusing. I think the bottom line is there are several ways to do this effectively and others may have ways that will work better for you.

    I'm up to my ears for a few days preparing a kid's lesson on short notice but I'll try to take some photos of what I like to use and how - easier to see than imagine from words! I have a bowl (dry maple) mounted in a spare chuck I can use to show how I like to shear scrape. A picture is worth a 1000 words. (We used to say that means a word is worth a milli-picture...)

    JKJ

  5. #20
    Since I use scrapers, all of my scrapers are sharpened with 70 degree bevels. If you are using a gouge, your included angles are more similar to a skew, so you have 'included' angles, probably in the 20/20 range, though jig sharpened gouges tend to have a thinner included angle that hand sharpened gouge wings. I have tried a shear scrape with the burr totally honed off (600 grit wheel, hone top on 600 grit diamond plate, then to the Tormek honing wheel, not grinder wheel). It does produce an edge you can remove arm hair with. I still prefer the turned burr to it. Maybe it is because I prefer all of my scrapers to have a burr, they just work better for me than that. On the grinder burrs, you do get a sharper edge with a 600 or 1000 grit wheel and it will cut better than the burr from a new 80 grit CBN wheel. Most of the time you don't need the more refined edge. I am trying to figure out if I just take the scraper fresh from the grinder and then burnish that burr down and up, pretty much breaking the burr off, do I get as good of a burnished burr that way as I do if I hone the burr off first.... No conclusions yet...

    robo hippy

  6. #21
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    Excellent video Reed, I always learn something new.

    In regards to using a bowl gouge I did try it several times. I think I am just clumsy or I can't focus for long enough periods anymore.
    Here is a video by Lyle Jamieson (probably where the sheer/shear discussion came in) on the bowl gouge.
    John K mentioned the other John Jordan video. Lyle uses a bowl gouge but John uses a scraper. One thing I found in common is Lyle states "you forget to breath while making the cut" and Jordan states that it is "difficult to talk and make the cut at the same time".
    https://www.youtube.com/watch?v=BDIvtr7StuA

    To me having the tool handle about waist height compared to way down makes the cut easier to control so I use a scraper.
    I checked mine and the angle is about 70* but that is the way it came. I did modify to a more spear shape but not rounded.
    The rounded is great for inside and out but I have never mastered honing a curved shape. I can re-hone the spear point on a diamond plate the same as a skew. After Reed's video I do plan to round the very tip (about 1/8") just to get rid of the sharp point.
    "I became insane, with long intervals of horrible sanity." - Edgar Allan Poe

  7. #22
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    honing curved edges

    Quote Originally Posted by Michael Mills View Post
    John K mentioned the other John Jordan video...

    ...The rounded is great for inside and out but I have never mastered honing a curved shape.
    Just a technicality but I didn't get this from the other Jordan's video but from what he told me and showed me. I have his two-ended scraper and it does work well, especially on wet wood, but I still prefer a gouge for my turning.

    For honing a curved edge I've tried a lot of ways, some recommended by great turners. What I find best (for me) are these little EZE-LAP paddle hones:

    hones.gif

    Note that I sharpen my tools on an 8" or 10" CBN wheel giving a concave grind.

    The pad is 3/4"x2" and flat to the very edges unlike some similar hones. I hold the handle and put my forefinger on the top of the paddle just over the diamond pad. I put the pad on the gouge or skew against both the edge and the heel of the bevel. With the finger pressing down, I find this perfectly controllable for honing the edge of a concave grind. I have never been able to hone with either the credit card size diamond hones or the larger hones.

    I mostly use the blue Extra Fine hone for cutting tools, sometimes the Fine for scrapers just before burnishing a burr. These little hones are not cheap but they last a long time.

    For the type of 1/8" thick Sorby curved inside scraper/cutters I usually just grind the profile perpendicular to the flat sides then use a fine hone flat on the sides. This is not quite the way Sorby says to grind but is the way StewMac recommends grinding their wonderful hand scrapers: https://www.youtube.com/watch?v=a7XRbfbpXiE As mentioned, I sometimes follow honing the flat on the Sorby cutters with burnishing a burr if I'm not getting the shear scraping I want or if I want a more aggressive (non shear scraping) edge for the inside.

    JKJ

  8. #23
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    Lmao...............

  9. #24
    Great video !! What did you raise the bur with ( at about 12 min.)? Carbide ? Diameter ? Carbide grade ? Best place to but it ? Keep up the videos I learn an awful lot from them. Thanks a lot.

  10. #25
    The burnisher tool is a 1 1/2 inch by 3/16 inch micro grain carbide rod. I googled it and found a source. I have a few left if you PM or e-mail me. I probably should suggest it to some of the catalog companies as there seems to be a lot of interest in it...

    robo hippy

  11. #26
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    Quote Originally Posted by Reed Gray View Post
    I probably should suggest it to some of the catalog companies as there seems to be a lot of interest in it...
    I haven't used my larger (5/16") carbide burnisher since I got the smaller 3/16" rods ones from you. The smaller diameter rod seems to burnish the same burr with less force, as expected.

    I know there was a big interest in the rods I got from you when I took them to a club meeting - I wish I'd gotten more!. (Do you have another 10 or so available?) A couple of people told me soon after that they made handles and are using them.

  12. #27
    I did just order some more. I do not sell them for profit. Here is a link to the company, and they 'will help any customer'. They are a small business. Price to me for 100 is about $1.35 each, not counting shipping. I did ask them about carbide cutters for the woodturning tools, and they were not familiar with them, but since every one is looking for replacement cutters, I will send them some links. Sounds like they can find custom items.

    https://centennialcarbide.com

    robo hippy

  13. #28
    Join Date
    Jul 2017
    Location
    Northern Illinois
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    I was looking to buy just one of the carbide rods for burnishing my scraper but at the company Reed linked above a 6" rod is around $5 but shipping is around $15. What other options do others use?

    Thanks,
    Tom

  14. #29
    Thomas,
    I sent a PM to you...
    robo hippy

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