Negative rake scrapers

[Reed Gray]

Can some one explain these to me... Yea, I am a scraper psycho, well, with normal scrapers... I use a couple of them, but they puzzle me.

One, what angles? I have one that is symmetrical with about 40 degrees on both sides so I can go either direction. My other one is 70 on the bottom and 20 on the top. I was chatting with Mike Waldt (hope you have seen his videos) and his is some thing like 45 on the bottom, and 30 on the top (have to go check now...). What angles do you use, and why?

I hear the term included angles, which I know means both of the angles, but don't really understand what that does for the tool. It probably has some thing to do with why with a standard grind scraper, no matter how high you raise the handle, it does not cut like a NRS.

With sharpening, maybe it is the CBN wheels, instead of standard wheels, but the burr seems to be fairly long lasting, though not like what I use for bowl roughing. Still playing around with my fine grit CBN wheels on the NRS, and it doesn't seem to make much difference. I have found that I can hand burnish a very fine burr on them as well, and it cuts pretty much the same as the CBN wheel burr, and can be burnished down and then back up a couple of times, like a standard card scraper.

It just doesn't work like I think it should, or I haven't figured it out. I do use it more for end grain turnings as shear scraping seems to cut at least as clean, and cleaner in most cases...

Mike said he didn't know enough about them. I talked to Stuart Batty about doing a video on them, and I could see the idea light turn on in his head, but haven't seen anything yet. I talked to Cindy Drozda about it, and she commented about a couple of people that were better with it than her, but still nothing...

robo hippy

[Bill Boehme]

Reed, I think that there are as many ideas about NRS as there are people who use them. I think that what I use is derived somewhat from Michael Hosaluk taught about a dozen years ago. Basically, my idea is to have a scraper where the included angle is a bit greater than 90° to make it less grabby. Also, I use them only for very fine final scraping to remove a feather thin shaving from the surface. The tool that I use has an angle of about 70° on the bottom side and about 30° on the the top side to give an included angle of 100°. I use a burnishing tool to put a bur on the edge because the bur from the grinder is too fragile. Obviously this tool won't work for anything that is warped because the tool pressure needs to be very light. I don't use it often, but occasionally it comes in handy.

[Fred Belknap]

Reed I am far from an expert on NRS but I do use them. I think my scrapers are around 75 degrees with a very small bevel on top. It seems to keep the scraper from self feeding thus preventing catches. I do mostly natural edge bowls and turn them twice so I don't use them on anything that is out of round. They seem to work better at a slower speed like below 1000 rpm. I have experimented with the pin bevel from Veritas and so far I'm not sure that it is better than the burr directly from the grinder. I have CBN wheels on my grinder, the 80 grit is the one I use on the scrapers. I always use scrapers to clean up both the outside and the inside. Been following your experiment on the finer grit CBN with interest.

[Roger Chandler]

I agree with Fred about the small angle of the top bevel. I have used NRS with about 20 degree on the top and 70 on the bottom...it does reduce the tendency of a scraper to self feed, and of course makes an edge good for shear scraping. I believe numerous combinations will work.

[Dale Bonertz]

Reed,
If you want to understand them contact Tom Wirsing. He is very knowledgeable about them. Not only on how to use them but the best angles, for him anyway, and why. Great guy and demonstrator. If you need his contact info please email me and I will give it to you. I think you still have my private email.

[Grant Wilkinson]

There is a write up online of a Tom Wirsing demo at the Rocky Mountain Woodturners. It says that he grinds his negative rank scrapers with a 20° bevel on both top and bottom, for an included angle of only 40°. For someone as ignorant as me about negative rake scrapers, that seems to be completely different than what most say are the ideal angles.

[Pat Scott]

I tried one angle on top and a different angle on bottom, and found it slow and a pain to adjust the platform twice just to sharpen. Also with a small bevel on top it was hard to see where exactly the edge was contacting the wood.

After taking a Glenn Lucas class I adopted his approach which is 33 degrees on the top and bottom for an included angle of 66 degrees. The bevel is the same length on both sides, so no matter which side you are using you can see the edge. Having the same angle/bevel on both sides lets me use either side as well.

The reason Glenn uses 66 degrees is because his angle gauge has a 66 degree notch and that makes it easy. 35 degrees top and bottom is fine also. I have notes from class that say Tom Wirsing uses 20 degrees top and bottom (40 included), and Kirk DeHeer uses 35 top and bottom (70 included). Stuart Battys Negative Rake scrapers came with a 50 degree included angle "for maximum burr size". The sharper the included angle the bigger the burr, but the more fragile the edge too. I think anything between 50 and 70 degrees included angle is probably fine depending on what you want or the wood. 66-70 degrees is a nice balance between burr size, strength, and longevity. Anything more than 70 degrees is getting too blunt, and requires more force to push the edge into the wood to get it to cut.

I leave my rest set at 33-35 degrees, and as a plus that's the same setting that I use for my skews, beading/parting tool, and I think one more tool I can't think of at the moment. Sure makes things simple and easy.

[Barry Richardson]

I use my wide skew laid on it's side, and it works great to clean stuff up, so I have renamed it my negative rake scraper, since I don't skew much....

[Reed Gray]

Well, I know the NRS is older than Alan Batty after hearing him tell how they made billiard balls out of elephant ivory, a couple of years process and using a NRS to take down the balls a hair at a time, and then let them rest. As for what works best for the included angles, that seems to be about personal taste, kind of like gouge grinds. How fine the burr is, seems to be highly variable. I have used a convex grind skew to adjust the shoulder of threaded boxes to get the grain to line up perfectly, but haven't compared another NRS included angle to compare.... For burnishing a burr, the Lee Valley tool would work on a NRS with a 70 degree bevel, but not on one with 30 or so on each side because it is at the wrong angle.... I may have to contact Tom...

robo hippy

[Roger Chandler]

I have not experimented to the extent some have with negative rake scrapers, but regarding the bevel angles, I do think a number of combinations will work well. I prefer a longer bevel length on the bottom grind and a shorter bevel on the top grind. With this I have not had any problem seeing the cut.....my top bevel is usually no longer than 1/8" to perhaps 3/16ths".

[Reed Gray]

I was able to google Tom, and sent him an e-mail. Not trying to be a commercial here, and this part can be deleted by the moderators if they deem it improper, but with my grinder rest, setting multiple angles is exactly repeatable and easy.

robo hippy

[Dale Bonertz]

I think Tom used to use 20/20 but I think he went to 22.5/22.5. I am not sure why but I am sure he can explain it. He is very knowledgeable with the negative rake.

[Kyle Iwamoto]

For the extremely uneducated people like me, isn't a 20 degree angle more of a skew than a NRS? That's what I use my skews for. (Like Barry) Yes, I do know that scrapers are way thicker than a typical skew.

Actually, I wanted to post this for Robo. How hard is it to modify your Robo Rest to a Tormek. That's what I use. Have a grinder, but none of the One way attachments.... (Continuing the "commercial") I have the grinder rest jig for the Tormek, but it's a PITA to set. NOT repeatable. I like your idea for the Robo Rest......

[Reed Gray]

I have been thinking about trying it. 2 main problems, one is the standard wheels are wider than the opening, and their tool rest bar would be in the way, so I would have to make another bar for the top of the Tormek. I did send a couple to some one who wanted to adapt them to the Tormek. He was going to cut the square tube off, and weld the upright onto the Tormek tool rest. Not sure how that would work though.

robo hippy

[Greg McClurg]

Rudy Lopez has a jig template on his website for his NRS. It is simple to make and works great. His website is rudolphlopez.com.

[Geoff Whaling]

Reed,
If you want to understand them contact Tom Wirsing. He is very knowledgeable about them. Not only on how to use them but the best angles, for him anyway, and why. Great guy and demonstrator. If you need his contact info please email me and I will give it to you. I think you still have my private email.

Tom was at Turnfest on the Gold Coast (QLD Australia) again just recently so I sat through his demos. I have to agree that Tom is a good demonstrator with great technique and some very good ideas on finishing cuts with NRS's. He also had a small 300 power digital microscope to show the burr on tools after sharpening with Alox and CBN wheels. Great demos.

[Reed Gray]

Well, I just had about a 30 minute chat with Tom on the phone.... Probably raised as many questions as I got questions that were answered.... Between us, he turns mostly dry wood, and I turn pretty much all wet wood, and that results in different end product and turning styles. Still to be answered are: wheel grit, angles, metals, burr types... Every one does things different. I am not done yet with figuring this out.

robo hippy

[Brian Kent]

Well you got me started on a negative path (haha). I took a thick scraper and used a belt sander. I am not even on the starting line, but thinking about how to start to try something.

[Reed Gray]

Well, for sure, the NRS is a clean up tool. The more I think about it (I blame Jimmy Clewes) you don't want a bevel rubbed finished surface because of the burnishing. The NRS takes care of it. Figuring out which bevel angles, and the specific burr is the questionable part.

The negative path.... Like an old song, Black Rose, which was about a woman said, "The devil made me do it the first time. The second time I did it on my own."
Snicker snicker......

robo hippy

[Geoff Whaling]

Well, I just had about a 30 minute chat with Tom on the phone.... Probably raised as many questions as I got questions that were answered.... Between us, he turns mostly dry wood, and I turn pretty much all wet wood, and that results in different end product and turning styles. Still to be answered are: wheel grit, angles, metals, burr types... Every one does things different. I am not done yet with figuring this out.

robo hippy

Tom is a great guy and very interesting to chat with as we had a few drinks with Tom & Melinda after hours. Had the same pleasure last visit too. His bowls and platters are superbly finished & yes he turns dry blanks that he has to purchase from interstate as there are no trees to speak of locally in his chosen home of Colorado. He can deftly use a NRS to produce wispy angel hair scrapings that are most likely "cuts" rather than "scrapes." Well worth sitting in on his demos, very informative and well delivered.

[Curtis Myers]

I attended Stuart Battys "7 Fundamentals of Turning" at last years symposium in Pittsburg. Below are from the notes I took during his presentation.
He had very positive things to say about neg rakes scrapers for finishing cuts. He said the angles should be the same and the combined angles should be less then 70 degrees.
Negative rake scrapper angle = same on both sides e.g. 25/25, 20/20, 30/30 but not 40/40
NRS must have a burr to be an effective finishing cut. Sharpen often. Without burr it is just a scraper, tearing fibers.

Stuart has 36 videos on Vimeo. Below link talks a little bit about NRS
https://vimeo.com/68652447

curt

[Bill Boehme]

If you have a skew with a curved bevel then you have an NRS ... no bur necessary. I found that my Alan Lacer slab-o-steel skew with the exaggerated curve makes an excellent NRS. I think that Richard Raffan has a similar one. I'm not too crazy about using a skew anyway, so designating it as a NRS makes me feel like I didn't fritter away more money in my never ending quest for that one tool that will prove to be my key to greatness. It meets all of Stuart Batty's criteria for included angle. Actually, my experience is that the included angle isn't critical. Nor have I found that both angles need to be equal. Stuart will be doing an all-day demo at our club this Saturday so I'll see what he has to say on the topic.

[Reed Gray]

"NRS must have a burr to be an effective finishing cut. Sharpen often. Without burr it is just a scraper, tearing fibers."

Curtis, I am not sure about this one. Either it is a misquote, or Stuart and I disagree considerably on this one, which could be totally possible because I approach scrapers differently. Standard scrapers, for all but the really hard woods needs a burr to cut effectively, and a NRS is a scraper. I had mine at 40/40 for a while, and now I am going to have to try the different angles on the same piece of wood to see what kind of difference it really makes. Since my platform won't go below 25 degrees, but that should be enough to be able to see some differences. I may need to get a couple of small skew chisels. Start at 25 and work my way up.

I have been playing some more with them... Had an old piece of ash that was very soft in some spots, and very irregular grain, and a piece of maple of some sort that was very highly figured. I can get an almost polished surface on the outside with a shear scrape and the 1000 grit CBN wheel. Kind of hard to shear scrape as well on the inside, but I have a core to try that out on. The NRS did clean up every thing on the inside. There was one 'difficult' spot where the grain and/or soft spot ran up the side of the bowl that was a pain. Got a good cut with a 60 degree gouge from the 600 grit wheel. Got a better cut with the 40 degree NRS and 1000 wheel burr. I need a camera that will zoom in a lot closer.... I have found the 70/20 NRS really nice for finish cuts on the inside of scoops...

The advantage of the equal angles is that some times I want to go on the inside of a bowl, and some times cleaning up a hollow form cove, I need to go the other direction. I am preferring a 1/4 circle type shape for the nose starting the arc at the nose. Some times I round the nose over a little so I don't have a point. Having a proper round point can come in handy for sweeping from the wall of a box to the center....

Dang it, looks like I may end up with as many NRS's as I have gouges.... Haven't tried a NRS Big Ugly yet... I have tried it on the 600 and 1000 grit wheels, and it didn't seem to make any difference at all. Still great for heavy roughing, and up on edge like a 70 degree bevel skew...

robo hippy

[Dale Bonertz]

Tom uses the 180 grit CBN for sharpening. I agree with having a burr on it. They work without it but seems to cut better for me anyway with a small burr. I clean up the top side then sharpen from the bottom side because that will raise a small burr. I don't feel the included angle matters that much. Mine are somewhere around 30 degrees on top and bottom. Like anything more acute and it gets a little sharper but won't last as long and not sure you'll notice much of a difference. I just used mine yesterday on a walnut bowl that I was having trouble with. Great for taking those little imperfections down.

[Reed Gray]

Anything to save on sanding time... I was telling Tom about my fine grit CBN wheels and I think he was drooling..... We will chat down in Atlanta.

I know some take a standard big heavy scraper to sweep across the bottom and through the transition of bowls mostly to smooth out the ripples that always seem to be there. Some will go all the way to the rim which I never do. That cut smooths out ripples, but doesn't remove any tear out. The NRS does seem to remove light tear out. I don't think you can ever totally remove tear out other than when turning end grain. You can get it down to minimal levels though.

robo hippy

[Justin Stephen]

Anything to save on sanding time... I was telling Tom about my fine grit CBN wheels and I think he was drooling..... We will chat down in Atlanta.

I know some take a standard big heavy scraper to sweep across the bottom and through the transition of bowls mostly to smooth out the ripples that always seem to be there. Some will go all the way to the rim which I never do. That cut smooths out ripples, but doesn't remove any tear out. The NRS does seem to remove light tear out. I don't think you can ever totally remove tear out other than when turning end grain. You can get it down to minimal levels though.


Reed, I use shear scraping (either with a Sorby shear scraper or a fluteless gouge) to hit spots like that. However, I do find the process to be a little inexact at times, by that I mean harder to control the exact shaping of these final cuts. It may have something to do with my body position or my eye position relative to the shearing cuts inside of a bowl.

Do you find NRS to be a better option than shear scraping for interior transitions, getting rid of the ripples, etc.?

[Reed Gray]

Well, on the outside of a bowl, shear scraping. On the inside, which is more difficult to turn smoothly than the outside, I have that same problem with shear scraping, and my gouges. Some days it is all smooth, some days it is the washboard. The NRS is still new for me, but sweeping it across does take out the ripples.

robo hippy

[Tracy Tame]

I would like to try a NRS or two. To those who use them, what is the profile you use most, bowl scraper, round nose, full round or square end?

[Reed Gray]

Most that I have seen are like a quarter round shape similar to a skew, so top or the arc is the nose, and it sweeps around to the side. This fits nicely into bowl curves, and can be used on hollow forms too. A full half round nose would work if you have different grinds top and bottom, like 30 on top and 50 on the bottom, then you could cut both right and left. I have symmetric grinds on mine so I just flip it over and grind the other side for a burr to go the other way. I have one skew with a straight across grind, that is about 10 degrees off square. I use it for tenons (yes, I do a few of those), and for trimming up the shoulders on threaded boxes where only the slightest bit needs to be removed. For boxes, I have more of a square nose and wing, with the inside corner rounded slightly to fit into the transition at the bottom of boxes. Never could do a square transition in boxes.

robo hippy

robo hippy

[Tracy Tame]

Thanks Reed, that is most helpful.

[Geoff Whaling]

I would like to try a NRS or two. To those who use them, what is the profile you use most, bowl scraper, round nose, full round or square end?

My Negative Rake Scraper's (NRS's) are effectively re-purposed skew chisels and are ground as such. They have a conservative short bevel with an included angle of around 60 degrees. One is a traditional skew design the other shaped some what like an Alan Lacer skew profile with much more curvature. Look up Stuart Batty's comments on NRS use etc.

NRS's have been around for centuries and are an adaption of tools used in ivory and blackwood turning by old school turners like Bill Jones and tools used by pattern makers.

[Curtis Myers]

Cindy Drozda has a nice two page article on NRS (see below link)

http://www.cindydrozda.com/handouts_Pdfs/handouts/demo%20handouts/negative%20rake%20scrapers.pdf

All the Best
Curt