I just don't get negative rake scrapers.

[Russell Neyman]

It seems like everyone is climbing onto the negative rake scraper bandwagon but, frankly, I just don't get it. I use scrapers all the time and get really good results with nary a catch. Perhaps that's because I grind mine at 85 degrees. I mean, by adding a "negative rake" to your scraping edge you're essentially making the grind angle steeper.

When I want to make the edge a bit steeper (effectively exposing more of the burr to the wood) all I need to do is raise my tool rest.

Somebody throw out a nugget of wisdom to convince me otherwise.

[Roger Chandler]

For me, the negative rake scraper is such a finesse tool, because it really takes the tiniest of shavings, and will allow for good clean up of difficult grain. The drawback is that the edge must be refreshed every 15-20 seconds depending on the wood you are trying to cut.

I saw Rudy Lopez use the NRS at our Virginia symposium, and while I had been using it all along, his instruction opened my eyes to how good they really are at finessing the grain so that sanding can a lot of times be started at 220-320 grit.

That was worth me purchasing a Thompson 1.25" scraper and making myself a totally new negative rake tool.

[Brian Deakin]

You may find the links below helpful

http://www.woodworkersemporium.com/content/NRS-Instruction-Manual.pdf


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

http://www.rudolphlopez.com/pdfs/Negative%20Rake%20Scraper%20Jig%20and%20Info.pdf

and

from 1 hour 32 minutes in video below

https://www.youtube.com/watch?v=N7BjRcSDurM&t=3093s

regards Brian

[John K Jordan]

It seems like everyone is climbing onto the negative rake scraper bandwagon but, frankly, I just don't get it. I use scrapers all the time and get really good results with nary a catch. Perhaps that's because I grind mine at 85 degrees. I mean, by adding a "negative rake" to your scraping edge you're essentially making the grind angle steeper.

When I want to make the edge a bit steeper (effectively exposing more of the burr to the wood) all I need to do is raise my tool rest.

Somebody throw out a nugget of wisdom to convince me otherwise.

I converted most of my scrapers to NRS after some experimenting. I find the NRS far easier to hold for finer and easier control than the conventional, flat-topped scrapers. The top bevel lets the scraper be held horizontal on the tool rest instead of angling the tool downwards.

Also, a NRS is easier to use inside a hollowed piece or bowl since the top bevel automatically "tilts" the edge while the tool remains horizontal.

Note that my scraper use is very gentle, to remove tool marks in dry wood. Those who remove wood or hollow aggressively with scrapers will work differently. As many things in turning, the tools and methods one person uses often depends on on the type of turning, the type of wood, and their level of experience.

If it wasn't such a long walk, I'd say stop by and I'll let you try a variety of grinds for yourself.

JKJ

[Reed Gray]

This is a video topic I need to cover, and I am almost there.... So, there are two types, one is more like a skew chisel, same bevel on both sides, in the 25/25 to 30/30 range, though that varies. The other style is closer to the standard scrapers with a 60 or 70 degree bevel on the down side, and a 20 to 30 degree bevel on the bottom side. Both styles cut with burrs. There are 3 ways to make the burr. One is straight off the grinder, standard grind, where you touch up the top side, and then regrind the bottom bevel with the scraper right side up. The other straight off the grinder burr is done by sharpening the bottom bevel with the scraper up side down on the grinder platform. Those who sharpen upside down claim it is a sharper burr. (It can be done on my robo rest if you tip the platform forward and slip the pin through the 90 degree hole so the pin rests against the yoke rather than going through the sleeves for about a -70 degree angle, thanks Kathleen Duncan for that tip). I have to play with this a lot more to see if I notice any big differences. First experiments seem to make me think that the upside down burr is weaker than the right side up burr, but not positive. The third method is to burnish a burr. With the skew chisel type NRSs, this does not work well because of the acute angle, you can actually hear the metal edge breaking as you burnish, no matter how gentle you are. The more blunt angled NRSs can burnish a very fine and very durable burr. The burr from the grinders are very fragile, and gone in seconds, making it a high maintenance tool. If you have to push at all, it is dull. The burnished burr is much stronger and, to me, it cuts better.

Now, for using them. On bowls, especially, much of it depends on the wood. Generally harder woods will result in a finer surface than softer woods. I do find them useful for sweeping across the bottoms of bowls, and barely into the transition area. I don't like them for going up the sides of bowls. They are still scrapers, and will pull on the fibers when you are cutting up hill, and generally I will get a cleaner surface with a burnished burr shear scrape rather than a NRS scrape. Again, that can depend on the wood. These are not tools to be used for any stock removal. At best you can smooth out ripples, but nothing more. I have used the burnished burr NRS for shear scraping some times as well Still experimenting, but I tend to want to hone off the grinder burr first because I get a better raised burr most of the time. Some times when I am feeling lazy, I use the grinder burr till it is dull, then burnish it down, then back up. The burnished burr can be turned down and bought back up a few times before you need to go back to the grinder. I do think the burnished burr on a standard 70 degree bevel scraper works better than the burnished burr on a NRS. No idea why, but more experimenting needed. Again, some times hard to tell because the particular wood can make a lot of difference.

I do love them for end grain, especially for boxes. You can leave glass smooth surfaces on most end grain, and with some practice, you can end up with surfaces that need no sanding. This is where I think the NRS excels beyond any other tool I have used.

I have been turning a lot of Bay Laurel (we call it Myrtle wood...) and the two logs I have are very different, and so are different parts of each log.

robo hippy

[Russell Neyman]

So, there are two types, one is more like a skew chisel, same bevel on both sides, in the 25/25 to 30/30 range, though that varies. The other style is closer to the standard scrapers with a 60 or 70 degree bevel on the down side, and a 20 to 30 degree bevel on the bottom side. Both styles cut with burrs. There are 3 ways to make the burr....

On bowls, especially, much of it depends on the wood. Generally harder woods will result in a finer surface than softer woods. I do find them useful for sweeping across the bottoms of bowls, and barely into the transition area.... I will get a cleaner surface with a burnished burr shear scrape rather than a NRS scrape.... At best you can smooth out ripples, but nothing more. I have used the burnished burr NRS for shear scraping some times as well....Again, some times hard to tell because the particular wood can make a lot of difference.,,,

robo hippy

At the heart of this is a topic that is largely a mystery to most woodturners: raising a burr. Truth is, you can create a burr (a small,sharp ridge on the topside of a sharpened edge) on any tool and put it to use, including bowl gouges. If anyone wants to understand this concept, watch a few videos on card scrapers, which I employ fairly often on the insides of bowls.

The point is, negative rake scrapers are hardly a replacement to "regular" scrapers and, while they can do a few things, really aren't helpful in removing large quantities of the inside of a vessel, which is what most of us use them for.

[John Keeton]

The point is, negative rake scrapers are hardly a replacement to "regular" scrapers and, while they can do a few things, really aren't helpful in removing large quantities of the inside of a vessel, which is what most of us use them for.Russell, I think this is an accurate statement except for the last clause. You may have been referring to scrapers collectively in your statement, but I doubt most of us use NRS to remove large quantities of wood. Actually, of those that use them and use them correctly, I would think just the opposite - that they are finishing tools only on face grain, though on end grain application they can remove more material cleanly. But, still, I think they should be viewed as a finishing tool to diminish sanding. But, I haven't surveyed the masses and perhaps my use of them is in the minority.

[John K Jordan]

The point is, negative rake scrapers are hardly a replacement to "regular" scrapers and, while they can do a few things, really aren't helpful in removing large quantities of the inside of a vessel, which is what most of us use them for.

This is true, they are not useful replacements for hogging tools. They are finishing tools. I use the NRS just after my finish gouge cuts and just before the hand scrapers or hand sanding, on bowls, platters, vessels, whatever, inside and out. Once you learn how effective they are it would be difficult to go back to other methods.

I also use negative rake scrapers for glass-smooth surfaces on end grain in good, hard, wood, such as on the bottoms and lids of lidded boxes. I've made a variety of shapes and sizes from 1/8" up.

Raising a burr on scrapers has been discussed here. I personally prefer burnishing a burr rather than rely on the ragged burr from a grinder which I remove by honing, just like preparing card scrapers.

JKJ

[Russell Neyman]

That's exactly my point. I use scrapers to hog out a ton of wood quickly, but the NRS is not useful for that.

[Roger Chandler]

I use a bowl gouge to hog out wood quickly, and in my opinion, the gouge is a much more proficient cutting tool. Plus, scrapers tear the grain, and a gouge cuts the grain, which cuts down considerably on sanding etc, with the right tool presentation........to each his own.

[Pat Scott]

NRS are finesse tools, they are not aggressive and will not self feed. It's nearly if not impossible to get a catch. You can shove the edge right into the wood and not get a catch (something you would never do with a conventional scraper). For these reasons a NRS is also a good choice for newbies or less experienced turners since the learning curve is practically nonexistent. Pick one up and a minute later you are getting good results. As others have said they are used flat on the tool rest. You don't have to worry about angling the edge or what angle the tool edge is at. Think shear scraping with the tool held flat might best describe a NRS.

[Reed Gray]

Standard scrapers have their place, and for me as a production turner, they are the most efficient tool for removing lots of bulk, especially from bowl blanks. On bowls, they don't leave a nice surface down the sides of the bowl, which is why it is called 'roughing'. They do a good job for sweeping across the bottom. I have heard the NRS compared to the shear scrape. These are two entirely different cuts. The only similarity between the two is that neither one seems to be able to generate a catch. The NRS is a scraping cut, with the cutting edge at 90 degrees to the rotation, and like the standard scraper, they do a better job of sweeping across the bottom, and not nearly as good of a job of going through the transition and up the sides of a bowl. The 'shear scrape' is not a scraping cut at all. It is called that because the tool is not guided by a bevel rub. The high shear angle does a much better job of gently lifting the fibers as they cut rather than pulling like scrapers do. How clean the resulting surface is depends on the wood, how sharp the tool is, and 'presentation' of the cutting edge to the wood. Most of the time, on bowl sides, I can get a cleaner surface with the shear scrape than I can with the NRS.

robo hippy

[John K Jordan]

...I have heard the NRS compared to the shear scrape. These are two entirely different cuts. The only similarity between the two is that neither one seems to be able to generate a catch. The NRS is a scraping cut, with the cutting edge at 90 degrees to the rotation, and like the standard scraper, they do a better job of sweeping across the bottom, and not nearly as good of a job of going through the transition and up the sides of a bowl. The 'shear scrape' is not a scraping cut at all. It is called that because the tool is not guided by a bevel rub. The high shear angle does a much better job of gently lifting the fibers as they cut rather than pulling like scrapers do. How clean the resulting surface is depends on the wood, how sharp the tool is, and 'presentation' of the cutting edge to the wood. Most of the time, on bowl sides, I can get a cleaner surface with the shear scrape than I can with the NRS.

robo hippy

I use this shape for the bottom, transition, and inside and outside of bowls. The flat at the end is perfect for wings, shallow dishing, and bottoms. For me, the shape is useful in more places than shear scraping with the wings of a gouge. I grind mine to 60-deg included angle, symmetrically so I can flip one over as needed, adding the appropriate burr of course.

411241 411242

These are Thompson steel, ground from his scrapers and a skew chisel. The surface is excellent in good wood, sometimes needing only a little sanding by hand.

JKJ

[Kent Weakley]

Russell,

The negative rake scraper is essential a regular scraper with a pre-installed downward pitch, also know as raising the handle.

Happy Turning,
Kent

[Peter Blair]

Russel this is my feeling exactly BUT with so many world class turners now using NRS I wonder if we are missing the boat. I for one can hardly wait for Reed's Video1

Russell,

The negative rake scraper is essential a regular scraper with a pre-installed downward pitch, also know as raising the handle.

Happy Turning,
Kent

[Brian Deakin]

Russel and Pete

Please view the diagrams and explanation in the video below

from 1 hour 32 minutes and pay particular attention to diagrams at 1 hr 38 mins

https://www.youtube.com/watch?v=N7BjRcSDurM&t=3093s

My understanding is the bur is on a different plane with a negative rake scrapper

hope this helps

regards Brian

[John K Jordan]

Russell,

The negative rake scraper is essential a regular scraper with a pre-installed downward pitch, also know as raising the handle.


I thought the same thing at first. Then I experimented and found out for myself: raising the handle does not make a scraper a negative rake scraper. There are several factors to consider but the most important is the tool is held horizontally instead of tilted down. This not only keeps the "downward pitch" constant but provides much more stability and makes it easier to use.

For example, consider the design I use, shown earlier, nearly straight for a bit on the tip then with a sweeping curve down the side, ground to a 60-deg included angle. The second picture also shows the little jig I made to set the grinder platform each time I sharpen.

412050 412051

I think this shape is perfect for the curve on the inside of a bowl or platter, for flat or almost flat curves, for the wings when "turning air", and for the outside of bowls and such, especially with ogee or other curves. I like to grind the same bevel on both top and bottom so I can flip it over and use the curve either way by just changing the burr.

It would not be easy or perhaps even possible to use a conventional scraper ground to this profile then by tilting it downward by raising the handle while at the same time sweeping it continuously along a inside, say, of a bowl shape. To keep the desired "downward angle" all the way up the inside of the bowl you would have to coordinate a twist while sweeping. The tool could easily become unstable. Grinding as NRS makes it extremely simple and easy to use.

I recommend that anyone who hasn't tried these grind one, put a good burr on it, and see how it works. Many, many people have been converted to the negative side or "discovered" this on their own, some after using skew chisels as scrapers. Always remember, it will barely work without a good burr. If you can't feel the burr with your finger when you slide it down the bevel and away from the edge there is not a useful burr. Most people add a burr while grinding but I get a better burr that lasts longer by using a burnisher. To renew the burr, I remove what's left of the worn burr with a diamond hone then burnish again - I repeat the several times before going back to the grinder.

JKJ

[Reed Gray]

Just raising the handle on a standard scraper does not give the same type of cut that you get with a NRS. Best explanation I heard came from Woodturner's Resource. What you get is a 'trailing' cut. If you have used the card scrapers, you kind of rub the bevel, and then tip the card and burr into the cut. When it starts to cut, you stop tipping the scraper. If you tip it too far, it starts to tear rather than slice. This is pretty much what you get when you just raise the handle of a standard scraper. Perhaps it is best said that the burr is not at the proper angle to get that cleaner cut. I have been turning a bunch of madrone and bay laurel/Or. Myrtle wood. The madrone takes a very nice cut up the sides with the NRS. The bay laurel does not.

robo hippy

[Russell Neyman]

Perhaps it is best said that the burr is not at the proper angle to get that cleaner cut.... robo hippy

Reed, a couple of years ago, when you attended a club meeting in Bremerton, you and I discussed sharpening a scraper upside down because there was a potential for a more effective burr. You said you'd give it a try and get back to me. What happened with that?

My own thought on it is, yes, the burr might be more pronounced on the backside of the grind, but I'm also unsure about the idea of trapping the tool between the wheel and the tool platform.

[John K Jordan]

My own thought on it is, yes, the burr might be more pronounced on the backside of the grind, but I'm also unsure about the idea of trapping the tool between the wheel and the tool platform.

I'm not Reed, but I'm with you. I don't like that idea either, one reason I think a reversible bench grinder would a useful!

But as I wrote earlier, I've tried all kinds of burrs and by far I like the burnished burr and for two reasons, because it lasts longer and because it can be reformed several times before having to go back to the grinder.

JKJ

[Peter Blair]

Brian, I watched it again, thanks.
Russel and Pete

Please view the diagrams and explanation in the video below

from 1 hour 32 minutes and pay particular attention to diagrams at 1 hr 38 mins

https://www.youtube.com/watch?v=N7BjRcSDurM&t=3093s

My understanding is the bur is on a different plane with a negative rake scrapper

hope this helps

regards Brian

[Reed Gray]

I do need to experiment more with the up side down burr. As for the potential for the tool being dragged into the grinding wheel, I am thinking that is pretty much impossible, more so because the blunt angle on the NRS. At least I would consider it far saver than the long extended V arm for sharpening the SRG... Can't remember if I already said it here, but this burr is more on the 60 or 70 bottom bevel, and 25 to 30 top bevel, rather than the shew chisel type. Eric Loffstrom did some micro photo or pictures of the right side/wrong side burrs. The more standard burr looked like little balls of metal kind of curled over, and the wrong side was more of a straight edge. What little experimenting I have done, the main feeling I have for it is that the standard burr is far stronger then the wrong side one, though the wrong side one is supposed to be sharper. I couldn't really tell any difference, but again, I need more experimenting. I do agree with John that the burnished burr is far superior to the grinder burrs. It is sharper. It is much longer lasting. Some times I use the grinder burr first, then when it is dull, I burnish it down then back up. I am experimenting with honing off the burr with a card type hone, then burnishing with the carbide rods. Actually, you can hone a very nice burr on the standard scraper, and the NRS. It seems like with the card hones, you never totally get rid of the burr, but it does get very fine. If I hone on my Tormek, then I can get most of that burr off.

robo hippy

[Reed Gray]

The more I ponder this, it makes me wonder... I remember the days when the honed burr on a standard scraper was one way to smooth out the bottom of the bowl. I think that faded when the NRS became popular. So, does any one use a honed burr on their NRSs?

robo hippy

[Kyle Iwamoto]

Robo, I'm not even close to being a pro, but I do use the honed burr. Learned that on the Boxmaster site. Since most of my sharpening is done on my Tormek, that doesn't work well with NRS. I also have a regular grinder, 350 grit CBN, which does nicely and does make nice NRS burrs. But I do like the card sharpener and burnishing rod burr best. It lasts only a few passes, but to refresh the burr, just swipe with the card a few times and a couple passes with the burnisher, and back to business. Don't even have to move from the lathe. Just my $0.02.

[Brice Rogers]

I've been enjoying using a NRS for a while. I would like to add another dimension to this discussion: the type of steel.

I'm wondering if really hard steel (IIRC V10 or M42, etc.) is better for NRS or is HSS or M2 better? On one hand the hard steel may keep the burr longer. But on the other hand, it may be a bit more difficult to raise the burr on the really hard steel. My tools are fairly cheap and are HSS. A few are only high carbon steel. So I don't have anything to compare to and would like the advice of others.

[Reed Gray]

Well, again, there is a lot of 'it depends'. The longest lasting burrs I get are on the Big Ugly tools. The tantung is much harder than any of the standard turning metals. I can also burnish a good burr on it. I would say that the V10 and M42 will have a longer lasting burr than the M2. The burnished burrs will out last the grinder burrs by a long time, and can be turned down and bought back up again several times. It is easier to burnish a burr on the M2, which can be done with a hardened burnishing rod, but it is difficult to burnish a burr on V10 and M42 unless you have a carbide burnishing rod. I am fairly sure the 'upside down' burr is the weakest of all, but not much experience with it...

robo hippy

[John K Jordan]

Most of my scrapers are 10V (CPM10V) from Thompson Tools. It is no problem to burnish a burr using a carbide burnishing rod or burnisher.

JKJ



I've been enjoying using a NRS for a while. I would like to add another dimension to this discussion: the type of steel.

I'm wondering if really hard steel (IIRC V10 or M42, etc.) is better for NRS or is HSS or M2 better? On one hand the hard steel may keep the burr longer. But on the other hand, it may be a bit more difficult to raise the burr on the really hard steel. My tools are fairly cheap and are HSS. A few are only high carbon steel. So I don't have anything to compare to and would like the advice of others.

[Pat Scott]

I'm wondering if really hard steel (IIRC V10 or M42, etc.) is better for NRS or is HSS or M2 better? On one hand the hard steel may keep the burr longer. But on the other hand, it may be a bit more difficult to raise the burr on the really hard steel. So I don't have anything to compare to and would like the advice of others.

I use two skews as NRS's for cleaning up the end grain on peppermills (one ground with a LH angle, the other RH). I use the burr straight off the 46 grit stone wheel on my grinder. I tried the burr off a 180 grit CBN wheel but didn't think it cut as well so went back to using the 46 grit wheel. I know the burr is bigger on a 46 grit vs 180 CBN, and for me and how I use them the 46 grit burr just works better.


I do not hone at all. If the burr only lasts 20 seconds, how much longer does a honed burr last?

I recently bought two M42 skews to replace my old worn out M2 skews. I hoped the burr would last longer on the M42 skews, but to be honest I really can't tell a difference. If anything it might be just a bit less on the M42. Maybe it's me, but I also seem to spend a little more time at the grinder trying to get a burr. With M2 it only took a pass back and forth, then flip and do the other side. With M42 it takes several passes back and forth. I've read so much from others that say M42 lasts so much longer between sharpenings than other steels that why would you buy anything else? These are my first M42 tools, and I will say I've been somewhat disappointed. Maybe if I used them like a skew was intended instead of scraping I would notice more of a difference. I wouldn't mind trying a M42 bowl gouge next.

[Reed Gray]

Pat, if your NRSs are the skew chisel type, same angle on both sides, then you already have a right and left NRS, it just depends on which side you sharpen on. I would expect little difference in burr durability on different metals with the skew chisel type of NRSs, mostly because there is very little metal under the edge to support the burr. With a 60/30 NRS, there is much more metal under the burr so it lasts a bit longer, though I don't know of any one who has tested to see just how much longer it will last. For sure, the burnished burr lasts a lot longer than any grinder burr. As for edge durability, I didn't really notice a difference with my bowl gouges until I had turned for while with the M42 and V10, then went back to M2. Huge difference in durability.

robo hippy

[Randy Heinemann]

I am relatively new to turning and, at first, didn't see the need to regrind my scrapers to turn them into negative rake tools. I actually still only have 2 tools that are negative rake; one a steel scraper that I reground, the other an Easy Wood Carbide with one of their new NR cutters. I love both, but only for finishing. I still use my other scrapers for cutting up to the last steps and my Easy Wood round and square cutters and my for hogging out large amounts of wood both inside and outside of bowls. I love my gouges for finish work and, so far, I can't find anything that gives me a better finish than gouges with light shearing type cuts. So, I get the NRS thing. We all use what we feel comfortable with and get the best results with.

[John K Jordan]

I do not hone at all. If the burr only lasts 20 seconds, how much longer does a honed burr last?


A burr honed with a diamond hone doesn't last long. It's about the same as a burr from a coarse grinding wheel except smaller. On the other hand, a burn made with a burnisher lasts a lot longer, at least in my experience.

JKJ