When do you use shear scraping vs a negative rake scraper?
What top angle do you favor on a negative rake scraper?
What top angle do you favor on a negative rake scraper?
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finish scraping
- Thread starter Kevin Jenness
- Start date
I turned for over 35 years before anyone "invented" the current negative rake scraper. I bought a negative rake scraper, and now it's in my misfit, unused tool drawer. Most of us used the Irish grind bowl gouge, skew, or freshly ground scraper to do fine scraping in the past. I still think a fine burr on a big scraper is a better tool. A negative rake scraper is NOT a necessity. It is a great way to spend money if that is your goal.
I use a NR scraper all the time for cleanup and dealing with small tool marks and grain issues. Also good for those very very slight corrections in the curve on a hollow form or those tiny ridges in the bottom of bowl. Never bought one though. I get blanks of HSS on Amazon and grind them to shapes I need. Not expensive and come in a variety of thicknesses and widths. I grind mine to 45 deg on both sides. I can flip them over from time to time and get more mileage out of the steel. I don't put a handle on them and put a different shape on each end.
I use D-way NRS’s. They have 20 degrees on the top angle and 70 on the lower angle. I prefer the NRS’s over conventional scrapers. They are less aggressive. I like to shear scrape on the outside of the bowls and NR scrape on the inside.
If your scraper is too aggressive, you are not using it correctly. The back of the handle must be higher than the cutting burr. Drop the handle too much and it will self feed. Keep the handle up and it will make the same whisker fine curls as a negative rake.
Agreed.
I use both, and for different things. On the outside of bowls, platters, and many other things, when it comes time to get a nice clean finish, AFTER a couple passes of finishing cuts when I still feel the wood needs to be even cleaner, I sheer scrape. Sheer scraping works well on the outside of these items, including spindles, and can produce an exceptionally clean surface. For this purpose, I use an Irish grind (ellseworth would be a kind of Irish grind, really), which provides the appropriate swept back wing to achieve the high angle you need for sheer scraping. The goal is to get that ultra fine, fluffy SHAVING, ideally (you might get dust with somethings, but that should go away and you should get a shaving once you have cleaned up things like tearout...you should only get fine dust while tearout still exists.) Again, this is only for the outside of bowls, platters, etc.
I use scrapers, including negative rake scrapers on the inside of bowls and platters, and I guess also boxes (this is newer for me though.) A swept back negative rake scraper is usually what I prefer to use (currently the one I've been is unavailable...sadly a nice sized chunk was taken out of it). This gives me the best experience cleaning up the inside of bowls and platters for the finest finish I can achieve. It allows an easy transition from the bottom of the bowl to the sides, or along a continuous curvature for bowls or platters. I think I've generally used a rake angle of 20°-25°. IIRC the one I have used most, a Carter and Son, comes default with a 25° although I've ultimately ended up regrinding it over time to 20°, however since I have to get a new one, I've been looking at Stuart Batty's system and his replaceable-blade NRS. They by default use 20° although he offers then pre-ground at a number of different angles from 20-40°. The thing that has interested me in these in particular, is the steel. It is something called CPM 15V, and for the use case, based on the arguments Batty makes for this choice, it offers the longest burr longevity of any steel. It may not be the most appropriate steels for other tools, I don't know, but for tools that require a good, clean burr like an NRS, Batty's system sounds pretty interesting and the 15V steel sounds like the ideal choice for longest wear resistance:
NRS 2.5" Swept Back Inner Bowl (Body and Blade Options)
Advanced NEGATIVE RAKE SCRAPERS with Replaceable Blades (NRS) PATENT PENDING We have sold out of this NRS Body and have more in production. We will be shipping any backorders in August 2024 We have replaceable blades in stock. 3rd Generation Unsurpassed Performance NRS Stuart Batty pioneered and...
stuartbattytools.com
I haven't bought one yet. I think they may be having supply problems with the tariff stuff going on, not sure. The 15V Blade I think is around $90 (or at least it was)...the whole tool with a 15V blade is over $300. Its pricy! But, with my previous M42 steel NRS, while M42 holds and edge longer...we are talking about an NRS burr, so they don't last long regardless. IIRC the C&S cost about $200. The idea of spending only $80-90 on a replacement blade after a couple-several hundred regrinds, with steel that holds a burr much longer, is kind of appealing. In any case...he'll have to get back to manufacturing them again first. He's been out of stock for a few months, and maybe since the beginning of the year, on the 15V NRS and all his handles. If they don't come back in stock soonish here, I'll probably get another C&S.
Yes the 15V is more wear resistant than say 10V but it is more brittle. It can chip easily even in the cut dependent on the sharpening angle. As far as negative rake scrapers when I teach new students I show both types and espouse that the negative rake is safer simply for the fact that you don't have to remember to raise the back of the handle. For myself I can use either with exactly the same results one is not better at doing the job than the other when used properly.
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Unless you're working on the INSIDE of a bowl....
As often the case, much can depend on what and how you turn.
I use both shear scraping with the wings of a bowl or spindle gouge and a variety of negative rake scrapers, depending on a lot of factors, for example the type of wood, the shape of the surface, the grain orientation. I’ve made a bunch of negative rake scrapers, small and large, and they often have different angles. I have experimented a lot. BTW, I’ve bought one pre-made NRS and it works well but not any better than what I’ve made from scratch.
For me, the top angle doesn’t seem to matter as much as the included angle, but again, it depends. One grind doesn’t fit all. I make most of my negative rake scrapers with Thompson stock - I reshape his scraper stock, skews, or round bars to suit, then sharpen on a 600 grit CBN. I always remove the grinder burr and apply a burr with a hand-held burnishing tool.
For end grain I grind a variety of flat and curved shapes and sizes, some quite small.
For face work and side grain, I also use a variety of grinds but have developed a favorite NRS design. These have the same angle on the top and bottom so from the side so they look a bit like a cross section of a large-angle skew, maybe 60 degrees or so, usually with a combination of a curve edge and a flat or slightly curved tip, again depending. Where I burnish the burr determines which side is up. Using these on face turnings, followed by hand scraping, requires very little sanding.
All this sounds a little vague, but it would take a lot of writing and photos to describe in detail. A forum search should bring up threads with useful photos and messages. And grind some variations for yourself and experiment.
JKJ
My camera man has gotten more "in demand" but I REALLY need to do a video on NRSs. For me, the settings I use on my NRSs is 30 for the top side bevel, and 60 for the bottom side bevel, which translates to 25/55 in real angles. My platform is off by about 5 degrees. My reasoning for the different angles is that I have always figured that the burr needs some actual metal under it to support the burr, other wise, it is gone in seconds. I had one NRS that was ground to 45/45, and the burr would vanish very quickly, even a burnished burr. so I reground it to 30/60 settings. D Way actually prefers the upside down burr for cutting, reasoning being that the upside down burr is sharper due to its upside down nature. I don't think it is any better than the right side up one, especially if it is a burnished burr. For my burnishing, I use a carbide burnisher, and I do not strop or hone the grinder burr off. When it gets dull and/or clogged with shavings, I burnish it down, then back up. Seems to work fine, and I can reburnish 3 or 4 times before I head back to the grinder.
Now, a NRS is still a scraper, and if not applied correctly, it can leave tear out since it is still pulling at the wood fibers. The secret to using it on bowls, both inside and outside is you want shavings "finer than frog's fur"! But Grandpa, I ain't never seen fur on a frog! That's because it is so fine! I would swear I heard that from my dad or grandpa, but dad said he had never heard it before. I have been playing around with Tomislav's 45 to 50 degree scrapers for a finish cut since he seems to have such success with it. As near as I can tell, it does seem to work better on finish cuts that are finer than frog's fur, and on dry wood which I almost never turn. At present, I still prefer a shear scrape with a burnished burr for the final passes on my bowls, all of which are once turned, then dried before sanding. I have yet to sand out my "experimental" bowls, some of which were dry. Just got a Bay Laurel/myrtle log yesterday, so, more experimenting ahead.... I do use a spear point scraper on the outsides of the bowl, and a round nose or ) nose shape for the insides of a bowl. A NRS and/or a standard scraper do better on the bottom of a bowl or platter since the grain is pretty flat so you are not running uphill against the grain. NRSs excel on end grain. With my threaded boxes, I never sand the insides of them since even 400 grit roughs them up. I do sand the outsides though.
robo hippy
Now, a NRS is still a scraper, and if not applied correctly, it can leave tear out since it is still pulling at the wood fibers. The secret to using it on bowls, both inside and outside is you want shavings "finer than frog's fur"! But Grandpa, I ain't never seen fur on a frog! That's because it is so fine! I would swear I heard that from my dad or grandpa, but dad said he had never heard it before. I have been playing around with Tomislav's 45 to 50 degree scrapers for a finish cut since he seems to have such success with it. As near as I can tell, it does seem to work better on finish cuts that are finer than frog's fur, and on dry wood which I almost never turn. At present, I still prefer a shear scrape with a burnished burr for the final passes on my bowls, all of which are once turned, then dried before sanding. I have yet to sand out my "experimental" bowls, some of which were dry. Just got a Bay Laurel/myrtle log yesterday, so, more experimenting ahead.... I do use a spear point scraper on the outsides of the bowl, and a round nose or ) nose shape for the insides of a bowl. A NRS and/or a standard scraper do better on the bottom of a bowl or platter since the grain is pretty flat so you are not running uphill against the grain. NRSs excel on end grain. With my threaded boxes, I never sand the insides of them since even 400 grit roughs them up. I do sand the outsides though.
robo hippy
I'm curious, since I'm in the market here. The Batty NRS system has blades made with 15V and 10V. If you were to choose one, which one would you choose? Would 10V be better, given its not quite as brittle, but should still offer longer wear resistance than M42 and certainly M4?
I agree with you that you don't have to raise the back of the handle...OR, tilt the scraper so only a corner rests on the toolrest. I've tried both, and I have less control with either. Tilting the handle up seems to make a normal scraper more...well, it seem to bite into the wood more. It may be a consequence of angles and natural forces, not sure, but I've never really had that problem with an NRS. I think that may be the key benefit of an NRS...that you get the softer less aggressive effect on the wood, with the full stability of the tool on the rest. I think that's a valuable difference.
I'd be interested in a video. Actually, I think it would be interesting to see you and @John K Jordan make one together!
I am curious about bottom angles as much as top angles myself. I have three or four scrapers I think. Two of them, are relatively thick, close to half an inch. For some bowls and platters, depending on the radius of the inside, I can "run aground" with the bottom of the scraper. I've adjusted the angle on one of these two, so that gives more clearance. With a greater angle it seemed to change how it worked, which surprised me...I thought the aggressiveness of the cut would be affected by top angle (and this was not an NRS, so the top was flat), but it seemed to change things. I then reground it again so it didn't have quite the angle on teh bottom, but then I ground the lower part of it again at a much greater angle, so it has a double bevel on the bottom now. That solved my more recent issues with scraping, where I couldn't quite get into the corner of teh inside of the bowls I was working on, and it seems to behave pretty close to normally.
Still, I don't actually know any of the theory behind bottom angles on scrapers. Would be really interesting of someone taught that, as most of what I've read or watched focuses on the top angles. A video covering comprehensive theory on scrapers would be really useful.
Here is the blurb from Batty's tools store on the steels used in his replacable blades, and their longevity/resharpen lifetimes:
The 10V itself supports a 350% longer edge hold than M42 (which is what Carter and Son tools are made from, and M42 has been quite good to me so far, I sharpen a lot less often than with classic HSS, which I think is M4 steel.) The 15V supposedly lasts another 50% longer, which I think means it should hast 525% longer than M42? I try not to leave the grinding burr on my scrapers. I try to hone that off, then apply a burr myself with a burring tool. I could probably use lessons on how to do that optimally as well (another thing for a video on scrapers? @robo hippy @John K Jordan
Anyway. This is a really expensive tool, but the 10V is $299 for the whole tool, which is 50% more than the C&S NRS. The C&S also doesn't have nearly the same kind of swept back edge as the Batty tool does, and I really like that long swept back NRS edge...
The 10V itself supports a 350% longer edge hold than M42 (which is what Carter and Son tools are made from, and M42 has been quite good to me so far, I sharpen a lot less often than with classic HSS, which I think is M4 steel.) The 15V supposedly lasts another 50% longer, which I think means it should hast 525% longer than M42? I try not to leave the grinding burr on my scrapers. I try to hone that off, then apply a burr myself with a burring tool. I could probably use lessons on how to do that optimally as well (another thing for a video on scrapers? @robo hippy @John K Jordan
Anyway. This is a really expensive tool, but the 10V is $299 for the whole tool, which is 50% more than the C&S NRS. The C&S also doesn't have nearly the same kind of swept back edge as the Batty tool does, and I really like that long swept back NRS edge...
I think you’re misinterpreting the point, Richard. It’s not that the standard scraper is too aggressive. Rather, the negative rake provides a more subtle result. I default to a freshly sharpened standard scraper, but there are times when I want a more delicate scrape. That’s when the negative rake earns its keep, for me at least. This is especially true when I’m in a deeper vessel and need to hang more of the tool beyond the rest. NR scrapers are great for that IME.
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Broadly speaking, I shear scrape the exterior of the vessel and use a scraper (standard or NR) to hollow out tighter curves on the inside. That said, I still prefer a bowl gouge when the interior angle permits.
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I saw something a while ago about negative rake carbide inserts. I was very sceptical but I bought one anyway just to try. It’s a 15mm round I think. I was quite surprised how well it worked. I’m sure it will come in handy for the inside of small stuff.
My favorite grind for face work and side grain, along with the aid I made to set the platform angle the same when sharpening. This picture shows the edge view.
This picture is of the profiles. I keep several and mark which side is Top so I don’t confuse myself by accidentally burnishing from the wrong side. Shaped from Thompson scraper and skew stock, they do take a bit of time for the initial shaping, even on a 60 grit CBN wheel. Use a 600 grit CBN to sharpen. The flat on the end is incredibly handy on platters, winged, platters, and mostly flat rims and such.
Note: these are used so gently (a “whisper” cut”) I never put them in handles. In fact I sharpen the tangs into other NRS shapes, all used hand-held.
JKJ
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Not a video, but an article from American Woodturner Spring 2006 by Stuart Batty. You may find some answers in it. The included angle of an nrs needs to be <90° to raise a useful burr. Batty recommends 45° to 75° included angle. I use 60°, 30° top and bottom. I want equal angles top and bottom so the tool can be flipped to be used either direction.
Jon, I for many years was in the Thompson Tool booth every year selling his tools. This is the guy who makes them. He did make some of the gouges in 15V and he stated that 15V is more brittle than the 10V steel and I have seen that on a 15V tool, it has not happened to the one I have as it does not get used very often (the only time I use it is when I'm showing someone both the 10V and the 15V. I cannot tell the difference in the cut between them). The 10V steel lasts more than enough in sharpness. Plus the fact that I don't believe in the burr raising line. I'll say this again, I have seen many pros say to the crowd that the burr only lasts seconds. Then he puts it down after using it for a minute or two. Then later he picks it back up and uses it again. Most of my steel is 10V but next to my Powermatic is a rack of misc. tools, in there is a Robert Sorby 1" HSS scraper and usually I'll just pick it up and use it and it works great. It has not been sharpened in years yet it works without a problem (not a NRS). I have some HSS, some M42 and a lot of 10V steel and I have never did a test as to how long they last as I have left that for others. And there have been many of those and it stands that in terms of lasting in sharpness the ongoing conclusion is that (not including 15V) its 10V, then M42 and then HSS. Remember that when a pro tells you that what he is using is the best its because he's getting something for using them or he is selling them. You will only know for sure if it is by buying them all and finding out for yourself. And with that I will tell you that when teaching I tell the students all of that and that I tell them now days that Thompson 10V tools and Hunter carbide are the two best choices in each of those two categories in my estimation.I'm curious, since I'm in the market here. The Batty NRS system has blades made with 15V and 10V. If you were to choose one, which one would you choose? Would 10V be better, given its not quite as brittle, but should still offer longer wear resistance than M42 and certainly M4?
I agree with you that you don't have to raise the back of the handle...OR, tilt the scraper so only a corner rests on the toolrest. I've tried both, and I have less control with either. Tilting the handle up seems to make a normal scraper more...well, it seem to bite into the wood more. It may be a consequence of angles and natural forces, not sure, but I've never really had that problem with an NRS. I think that may be the key benefit of an NRS...that you get the softer less aggressive effect on the wood, with the full stability of the tool on the rest. I think that's a valuable difference.
I very much agree. Based on my own experience, not just what I heard someone say.
JKJ
So...I can imagine a GOUGE, is probably more subject to issues with brittleness, than the burr on a scraper, especially an NRS. Right? I don't think I'd choose the most brittle steel for a gouge, I think you would want a bit more flex for something that is often used quite aggressively to remove large chips of wood fast.
The 15V and 10V steel, I was thinking about explicitly in the context of NRS and the longevity of the burr.
Regarding scraping with or without a burr...I don't have 30 years of experience behind me, however, I have several scrapers, and I used to never sharpen them. I sharpen them fairly frequently these days, and I do find there is quite a difference between a recently sharpened scraper with a good burr (especially one I've honed the grinder burr off and put my own on) and one I haven't sharpened for some time. I can certainly make a never-sharpened scraper work. My experience is, they don't work anywhere remotely as well as a scraper with a good burr. I don't go by any particular specific timeframe, as far as for how often I sharpen. Its not like I sharpen them every 30 seconds, or every 2 minutes. I just use them until their effectiveness is gone, and then I resharpen. I don't even think that itself, has a consistent time...it depends a lot on the wood. But when I can no longer just touch the cutting end to the wood and pull it along and get nice fluff or super fine dust, then I assume the burr is gone, and sharpen again. I'll use it until it no longer seems to be working most effectively, and sharpen again. The goal I've generally had, is to get that super fine shaving/dust, which to me has always been the indication that my scraping is doing a FINE job to clean up the wood surface to a FINE surface.
Now, I know you can use a scraper to hollow. I've watched some videos by Richard Raffan where he hollows bowls entirely with a scraper. I've always found that interesting, but I haven't actually tried it myself much. I imagine that if you are doing that, then a burr doesn't matter, and the bulk of the tool is really what's taking the wood out. So I could see an argument being made in that context that a burr does not matter, and that a scraper not sharpened in years is fine. Different use case, though, right?
My interest in the 10V and 15V has been strictly for an NRS, with regards to the longevity of its burr. I don't think I'd buy a 15V gouge, though. I'm quite happy with my M42 C&S gouges, skews, etc. for most things.
Well, maybe look up my video about "Scary Scrapers". Bigger and thicker scrapers are not safer. The problem with bigger scrapers, and this is mostly in the transition area of a bowl, you can get way too much cutting edge into the wood at one time, and that is what makes them "self feed" and/or catch. As for V10 and M42 HSS edge durability, I think those numbers are inflated. As near as I can tell, there is almost no difference in edge durability. This is the same metal that bimetal bandsaw blades and chain saw teeth are made from. I have a friend that had turned for 60 years and asked him about the differences between the two metals, and he said there was no difference. As for edge durability, again, the skew chisel was the first NRS. Now they are far more specialized. The most durable and long lasting, and sharpest edge you can get is a burnished burr, similar to what you do with a card scraper. I do not remove the grinder burr, just burnish it down when it gets dull, and back up again. I have found that the burr to last longer, you need some metal under it. The standard skew chisel the burr disappears in seconds, and the burr is what does the cutting.
robo hippy
robo hippy