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Thread: Card scraper hook - how long does it last?

  1. #1
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    Card scraper hook - how long does it last?

    I've reviewed on-line resources until my fingers are blistered, and I finally got a half-backsided edge on my card scrapers.

    I'm filing down with a fine single cut file, using a wood block as a template to remove imperfections;
    I then smooth the edges with a 4000-ish grit DMT diamond plate, being as close to perpendicular as I can - sharp edges on both sides.
    I then smooth the sides of the plates using the same 4000 to try and make a proper 90 degree surface.

    First question; in drawing out the steel (it's on the granite top of my Rigid table saw) how much pressure do I need to put on the scraper? I use a Veritas Tri-burnisher, and I swipe it in my mineral oil soaked rag before using. It applies to my 2 scrapers, a Bahco and a generic Lee Valley.
    Second; I do get a very small hook, but I'm working with Oak, and I'm not getting the kind of shavings the on-line videos show. I'll keep working on technique, obviously.
    Third; again, using Oak, how long should to hook last. It seems I scrape one or two small areas, and I have to go to the next edge. Is this a function of the poor hook, or not enough pressure in working the initial edge, or what?
    I know it's nearly impossible to diagnose this long distance, but any hints would be appreciated.
    Last edited by Aaron Rosenthal; 05-24-2020 at 1:28 PM. Reason: Spelling
    Young enough to remember doing it;
    Old enough to wish I could do it again.

  2. #2
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    I burnish the edge, try it, burnish some more, try it, repeat until it's good or I've ruined it then start over. In addition to the pressure there are other variables such as the angle of the burnisher to the edge. Burnishers with smaller radii need less pressure then large radii. The Arno triangular burnisher I use the most these days needs the least pressure. I don't have a picture.

    _scrapers_IMG_7784.jpg

    Before burnishing, I do use an extra fine diamond hone on the flats of the sides and on the edge itself, but for the edge of the card I use a small jig to keep the hone perpendicular to the edge. This idea came from a FWW article Dec '18, I think.

    scraper_jigs_IMG_7887.jpg scraper_honing_1_IMG_7884.jpg scraper_honing_2_IMG_7881.jpg _scrapers_IMG_7818.jpg


    My scrapers are mostly curved for use with woodturings and I rarely use oak so can't answer that. I can't even say how long an edge will last in general because it depends.

    scrapers_favorite_IMG_7870.jpg

    If you want to avoid the burnishing completely try the StewMac (Stewart McDonnald) Ultimate scrapers, marketed to instrument makers. Two of the rounded ones shown. They are expensive but amazing. Maybe not so good for wide boards when making furniture.

    JKJ

  3. #3
    I feel like my edges last longer than they should. Granted, mostly I'm using it only for problematic things here and there, but occasionally it gets a real workout and my fingers give out before I even make it through the second edge. I can only say that after being utterly frustrated I watched this video and then EVERYTHING changed.


  4. #4
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    I watched the same video Chris posted some months ago and have been doing OK with these. I do use a store bought carbide burnisher.

    Also, at the rolling the hook stage I put the scraper in a vise with a hardwood block. I have a piece of maple 1.5 x 1.5 x 10 inches for that. I set it up with the scraper sticking up an eighth or maybe three sixteenths above the maple. So I have a right triangle, the 3/16" height of the scraper is leg, the 1.5" thickness of the maple is the other leg, with the carbide burnisher resting on those two points making the hypotenuse. I usually make a gentle pass with no pressure to make sure the burnisher isn't going to hit vise parts, and then using this crutch I can roll an even burr.

    Edit to add, I have worked very little oak. My edges don't last as long in harder woods. You might try not rolling a hook at all and see how it does in your material with just the edges dressed square. I read somewhere for marquetry they don't burnish at all, just get it square.
    Last edited by Scott Winners; 05-24-2020 at 4:57 PM.

  5. #5
    Try using a medium stone before the fine one. Jumping from a file to 4000# may be leaving file scratches in the burr that weaken it. Using a jig such as John's will help to keep the edge square.

    A few ounces of pressure is enough on the burnisher- a small hook is stronger than a big one, and can be redone several times before refiling

    The video Chris links to shows that you don't need to be overly technical to get a useable burr.

    Just filing the edge should produce a burr that will cut oak cleanly enough to start sanding at 150#, but it won't last as long or cut soft woods as cleanly as a sharpened and burnished edge, and when it is dull you have to file it again. That's how I prep scrapers for rough work like scraping glue.
    Last edited by Kevin Jenness; 05-24-2020 at 11:05 PM.

  6. #6
    When I worked in a violin shop, I was taught to just file the edge and go to work putting a radius in a very hard ebony fingerboard. I only recently have learned about further refining a scrapers edge, but did just fine shaping ebony with a simply filed edge, that only needed filing but maybe once a week. After learning what people do with scrapers I was surprised how well I worked for years without this knowledge, but after watching the video that Chris posted is makes sense that it would take a fine edge to cut and not crush softer woods, but a duller one could do just fine in a very hard wood. In my experience, Oak is quite hard, perhaps try just filing the edge and going to work?

  7. #7
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    I also use the Veritas Tri-burnisher or whatever they called it. One or two light strokes. The main thing I see folks err on is not spending enough effort on edge preparation and spending too much effort on the hook. I pull the edge once or twice and then turn the hook once or twice, then stop.

    Card-scrpr-shrpn (9).jpg
    "The Danish government believes that if we train 5,000 designers, and produce
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  8. #8
    The most important part of preparing a scraper edge is to make sure you get it perfectly 90 degrees, with the edge square and sharp and no rounding (this is critical) prior to turning the burr. For wood, a file is sufficient for this; you don't need water stones or diamond plates or anything else. For scraping a finish you do, but it isn't necessary for wood. I rarely ever use anything but a file to get the edge to 90 degrees. For learning, I definitely recommend only using a file, stones and plates increase the chances of rounding.

    To sharpen the scraper. I put it in the shoulder vise sticking up about an inch. I hold the base of the file in my right hand (I'm right handed) with my hand resting on the bench top to help steady the file and keep it square to the edge. I hold the tip of the file with my left hand. I hold the to file at a slight angle to the scraper and push the file a little while I go down the edge. After I get the edge to where it is square, I joint the edge like a saw, with the file parallel to the edge to make sure it is flat. After this I run the file along the side gently to make sure there isn't any burr from filing.

    After this I turn the burr with the back of a Pfeil carving gouge. I hold the gouge a little less than square to the edge, drop the handle so it is a little above the bench top, and go across the edge once. I then do the other side and then that edge is done. I haven't found that turning a larger burr is particularly helpful, so I don't go more than once. If anything, you increase the chance of messing up the burr or overrounding it.

    I then do the other three edges in the same way.

    I usually get 5-10 minutes of scraping from an edge. More if I am gentle, and less if I am aggressively pulling out machine marks. If you start getting powder, stop and redo the edge. At that point, all you are doing is rounding the edge and making it take longer to sharpen.



    For learning to use the scraper, my advice would be to forget everything you have seen/read in videos and books and just try it in every way you can think of, including ways they tell you not to. It really is the only way to learn. Push it, pull it, try different grips and numbers of fingers, with thumbs and without, one handed, two handed, bent, not bent, every angle relative to the wood, perpendicular to the wood, skewed, with the grain, against the grain, cross grained, and any other possible variation of technique you can think of. As long as you don't kink the blade, there is almost no way you can damage a scraper.

    Full disclosure, the scraper is one of my absolute favorite tools. I use it on nearly every project in some way. It just does things so easy and fast. I really should do a video or at least takes some pictures on how to sharpen one, one of these days. This is so much easier to show than explain. The other thing is after you get the hang of sharpening and using a scraper, you get kind of pi$$ed, because you realize how simple it is compared to how complex it gets explained

  9. #9
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    Try using one, straight off the file.

    Getting a stable, durable hook achieves best results but a sharp arris is often sufficient.

    Polishing on a stone will produce a continuous shaving, but it's not necessary.

    Most of the effect is achieved "springing" the steel into a curve that has a progressive cutting angle.

  10. #10
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    File: maybe, maybe not, depends

    Quote Originally Posted by Jim Matthews View Post
    Try using one, straight off the file.
    Getting a stable, durable hook achieves best results but a sharp arris is often sufficient.
    Polishing on a stone will produce a continuous shaving, but it's not necessary.
    Most of the effect is achieved "springing" the steel into a curve that has a progressive cutting angle.
    Yes, I agree it is useful and educational to try and evaluate different ways of preparing and using scrapers.

    The result may depend on the intended use and method of working.

    I file, hone, and burnish and use curved hand scrapers for smoothing curved woodturnings before sanding then sand with fine grits either by hand or with very gentle ROS action. The scraping leaves the surface so smooth I am often able to start with 400 grit and even finer. I show one piece in demos that was touched only by 600 grit.

    While teaching a private class at Arrowmont a few months ago, one person said honing and burnishing was a waste of time and showed his technique of going straight from a fairly coarse file to the wood. This certainly did create shavings and appeared useful. However, in testing later at home I found that filed edge left a very rough and relatively weak burr, similar to a burr directly from the grinder. The scraping left such a rough surface I had to resort to much coarser sand paper to remove the scratches left by the scraper. I tested with with hard, fine-grained wood.

    My take-away is yes, I could scrape straight off the file. But no, I could not get as smooth a surface. Also, burr did not last as long as the burnished cutting edge. Scraping with a coarse burr may be OK to remove wood to shape the part, but in my use the part is already well shaped when I take it off the lathe and and my use for hand scraping is to remove remaining tool marks and prepare the surface for sanding with fine paper.

    The file burr seems somewhat analogous to woodturners who prefer to use negative rake scrapers with the burr directly off the grinder. This works, but the life is so short (reported to be 20 seconds or less) that the tool must be returned to the grinder often. (Keep in mind that negative rake scrapers used at the lathe are subject to MUCH higher abrasion since the much more wood is passing the scraper, perhaps 1000 inches per second or more.) In contrast, a NRS that is honed and burnished properly will last much longer and provide a smoother surface to boot.

    Just my experience.

    JKJ

  11. #11
    Quote Originally Posted by John K Jordan View Post
    ... In contrast, a NRS that is honed and burnished properly will last much longer and provide a smoother surface to boot.

    Just my experience.

    JKJ
    What is your honing process for NRS's?

  12. #12
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    Lots of good info in this thread, and somewhere in the middle is what will work: what works is dependent upon the type of wood you work and your style of using the tools.

    I've gotten shavings from a card scraper just filed, but it needed further work! I find my longest lasting burrs result from modest scraper prep, including filing and then honing on a stone the edge and the sides adjacent to the edge. In turning the burr, too much is bad: a couple of passes with the burnisher, without too much pressure. I've tried a variety of burnishers and shapes, with the best (for me) being a thin, round burnisher.
    If the thunder don't get you, the lightning will.

  13. #13
    The old guys I worked with mostly used agate burnishers, I have not tried one. They were not just random pieces of agate, they were a commercial product made for burnishing. I use an old carbide laminate router bit.
    I did buy a steel burnisher once ,I think it was a Stanley. It was too soft, absolutely worthless as a burnisher.

  14. #14
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    Quote Originally Posted by Karl Loeblein View Post
    What is your honing process for NRS's?
    I use a number of negative rake scrapers on the lathe. These are my favorites for bowls and platters.

    _scrapers_IMG_7778.jpg NRS_IMG_7907.jpg

    I use an Extra Fine Eze-Lap diamond paddle hone and simply hold it against the bevel hone away the grinder burr. Then burnish a burr. When the burnished burr gets dull, I often hone it away and burnish again. This works several times before I go back to the grinder. The plastic template lets me set the angle of the tool rest for a perfect repeat of the same ground bevel.

    I use smaller NRS for other work, in a lot on end grain for things like lidded box bottoms and lids, decorative recesses on bowls and platters, etc. I made a number of them and hone and burnish the same way. This shows just a few.

    scrapers_small_thompson.jpg

    These are the hones I use for almost everything. The blue one is the extra fine I use on NRS. I like these far better than the DMT and others I've tried. They are not cheap but last a long time. I'd hate to be without them so I years called the company and ordered a life-time supply which in quantity were far cheaper than I could find them in the woodworking stores.

    hones.gif

    JKJ

  15. #15
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    Neanderthal? Really?

    I just can't believe the contortions and expense the internet has fostered in the use of hand tools and especially the preparation and use of the simplest tool on the bench. Obviously, there are those whose specialized work require departure from the basics but someone who is inquiring as a new user deserves to know about "A" before proceeding directly to "Z".

    You put the card in the vise and run a 1/2 mill file at right angles across the edge. Then you run the edge across a fine stone at right angle to the edge a few strokes, then on the flat a few more strokes. Put a drop of oil on your fingertip and tub it on the edge and flat near the edge. Now place the card flat on the bench so it overhangs just a bit. With any burnisher or really hard chisel bend down, holding the burnisher at just a few degrees off 90 and lightly push the burnisher across the edge one end to the other using the full length of the burnisher. The same motion as using a file. 2 or 3 or sometimes four passes will create the burr you want.

    The scraper is then used close to 90 degrees to the work surface, pushing it only slightly into convex with the thumbs. If you need to angle the card more than a few degrees off 90 you applied too coarse a burr. Start over.

    When the scraper fails to yield nice shavings, simply lay it flat on the bench and pass the burnisher, also flat, over it a few times which will remove any remaining burr making the "tick-tick" sound that's characteristic and re-apply the burnisher to the edge. Just like a plane blade, it isn't necessary to go back to the file and stone for quite awhile.

    Or buy yourself a $1000 imported belt sander and forget the whole thing.

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