Negative Rake scraper vs. regular scraper

[Stark Suggs]

NRS....never used one. It seems that there is a huge difference in the way they are sharpened, burr angle degrees, their formation, but certainly technique. I have worked mostly with green/wet wood making bowls and have enjoyed it. "Regular" scrapers have served my well since I've been turning. My preference is the larger ones with substance...high quality steel... So, What do you think? What serves you best? Your vies on NRS bevel angles? Technique? Thanks!

[Reed Gray]

I need to get to making a video about the NRS... Not sure if you have seen the one I did called 'Scary Scrapers'. As for the NRS, there seem to be two types. One is the skew chisel, generally about 30 degree bevel on both sides, the other is closer to the standard scraper on the bottom, 60 to 70 degrees, and a top bevel in the 20 to 30 degree range. Now there are carbide ones as well, but I have no clue as to how they work. How cleanly a NRS cuts depends on the wood. For end grain surfaces like boxes, you can get a 220 to 600 grit sanding finish, and even on softer woods. With bowl grain orientation, some woods will cut very well, and some not. Most of the time this is related to hardness and the structure of the wood. Harder woods will generally cut more cleanly than softer woods. If the wood has an interlocking grain, then it gets a smoother finish cut with a honed or 600 grit wheel ground gouge. Most of the time, the scrapers all have a burr on them. The standard scrapers are generally best with just the grinder burr for heavy roughing. If I am doing shear scraping with my scrapers, then I prefer a honed bevel, then a burnished burr for the cutting edge. Some prefer an upside down sharpening for their burr. I haven't played around with that one enough to be sure about it. For the NRS, most use the grinder burr, which makes for a high maintenance edge, which is only good for seconds. I prefer the burnished burr here, again because it is sharper, and lasts a lot longer and is simple to burnish down, then back up again several times before needing to go back to the grinder. The skew chisel type of NRS does not burnish well because there is no metal under the edge to support the burr. You can actually hear the edge fracturing as you try to burnish the burr on. One point I make in my Scary Scraper video is that you don't need a big heavy duty scraper, 1 inch wide is more than enough to stall any lathe I have ever turned on...

Oh, for burnishing, I use the carbide rods. I did hear about using a ceramic rod which some say is better, but haven't tried it yet...

robo hippy

[roger wiegand]

What Reed said. Darn near impossible to hone the upper bevel so you can raise the size burr you want with a burnisher (I'll use several different sizes in the course of a few minutes work). I predict it's a fad that will go the way of oval skews and other such "innovations" in a few years. Fortunately it's easy to make one out of any scraper you have if you want to try it and then convert it back later.

[John K Jordan]

...The skew chisel type of NRS does not burnish well because there is no metal under the edge to support the burr. You can actually hear the edge fracturing as you try to burnish the burr on....

Could this depend on the type and temper of the steel, the included angle, the amount of burnishing pressure, or the burnisher?

I use only the Thompson 10V steel, sharpen to 60 degrees included angle, and burnish with carbide. I use the NRS for smoothing after finish cuts in dry wood. I've not once heard or had a burnished burr crack/break while burnishing or in use. This is with either the carbide rods I got from you, a larger diameter carbide rod, or an Arno burnisher. I've ground the scrapers from Thompson scraper blanks, from Thompson skews, and from Thompson round rods of various sizes.

These are the shapes I use for bowls and platters. The middle one in the second picture shows the angle I grind.

_scrapers_IMG_7778.jpg scrapers_neg_rake.jpg

I grind these with a 600 grit CBN, remove the grinder burr with a blue Super Fine Eze-Lap diamond paddle hone, then burnish the burr. The aggressiveness of the burnishing determines how delicate or aggressive the shavings. After trying the scraper if it's not aggressive enough I hit it another lick with the burnisher. If too aggressive, I hone away the burr and try again.

JKJ

[Reed Gray]

John, I use a lot of Doug's and D Way tools, so most of my NRS's are the higher grade metals. Same with both of them. Not sure if I use any M2 or not. It takes less pressure on the skew chisel types than it does on the 60/30 types, but I can hear that crinkling noise on both. I don't use the skew chisels for anything other than spindles.

robo hippy

[Randy Heinemann]

I am new to NRS, but have initially found that the biggest plus for me is that they don't catch as easily. I can get a good finish with them but I can get a good finish other ways also. This is just what I noticed in my very beginning use of NRS.

[Stark Suggs]

Reed, and everyone, thank you for all the information on NRS. I'm going to take a close look at the scraper that resembles a regular bowl scraper. John, beautiful scrapers to say the least. Recently, I've had success burnishing the dulled grinder burr on a recently purchased 1 1/2" round nose scraper (Crown) and others....with a 3/8" burnisher previously used with my cabinet scrapers. The leftover burr gently rolled back up added a little extra life before returning to the grinder. Please take the following experience with a grain of salt. It very well may be another way of doing something that already exists. Always trying new ideas, I ran across an old "burnisher" inside the house. It appeared to be an antique (certainly not new) kitchen knife sharpener rod? The 12" rod has a low slope from base to the tip with the rods surface broken up into 4 sections...2 that are smooth, and 1 that has a fine file and the other with I'd call extra fine file. Both "files" run parallel with the rod's length and are not that visible. I've discovered that both polished sides burnish well, and both filed areas have interesting results. I've experimented with both a bowl dulled grinder burr and a lapped surface only (no burr) on my bowl scrapers. In both cases, a gentle roll plus an upward (perpendicular to the lapped back) push created a small sharp burr that cut and lasted well. The lapped back with no grinder burr produced a particularly sharp edge with a barely visible burr held under a bright light. 4-5 passes seemed about right. You can feel it forming with each pass. The result on bowls produced nice shavings and a smooth and shiny surface on figure. Take this with a grain of salt/face value etc... Lastly, if pictures will help, I'll get some posted. Thanks for reading.

SWS

[Stark Suggs]

.....of the two NRS you said..."the other is closer to the standard scraper on the bottom, 60 to 70 degrees, and a top bevel in the 20 to 30 degree range"...possible to give me a brief description of how you set one up, or a link to visit? Thanks

[roger wiegand]

I use a 600 grit diamond flat to erase the burr from the grinder, then raise a new burr with a carbide burnisher. One very light pass for a finishing burr, one heavy pass for a burr suitable for box hollowing in dry wood. I've never needed more than one pass to raise a substantial burr, my usual problem is keeping it small enough for a good finishing cut. Too much danger with multiple passes of making it uneven. None of these burrs are big enough to see with my old eyes. A good finishing burr I can barely feel with my finger-- it still cuts like crazy.

[Stark Suggs]

Thanks Roger. Im fairly new to turning and using scrapers, which is probably obvious :- ). What I need to try is your approach on getting that tiny yet very sharp burr. My mistake has been too many passes...Appreciate the info!

[Stark Suggs]

Thanks for all of your input in this thread. I have not heard of an upside down grind, but it sounds like the scraper is placed face/flat side down and grind from there. Interesting. On a somewhat different note, I enjoyed watching the video where you make the bowl with just a scraper.....

https://www.youtube.com/watch?v=hKdq...d6AUAAAAAAADAA

Very cool. You make it look too easy. I really have a lot to learn which will take a while.... but having a blast doing so.

SWS

[John K Jordan]

Thanks Roger. Im fairly new to turning and using scrapers, which is probably obvious :- ). What I need to try is your approach on getting that tiny yet very sharp burr. My mistake has been too many passes...Appreciate the info!

It's difficult to compare the burnishing methods used by two people since one may use more or less pressure than the other. Also, one may hold the burnisher at a different angle relative to the upper bevel of the scraper which can make a big difference. The type and hardness of the steel scraper is another factor.

Also, the diameter of the burnishing rod makes a difference in the pressure and the number of passes needed. I have three burnishers. The smaller the diameter, the less pressure needed for the same burr. The Arno burnisher has both round and triangular carbide burnishing rods. The triangular one has a smooth, polished radius instead of a sharp edge so it works like a very small diameter rod. It takes far less pressure than the largest burnishing rod I have. The largest one is still probably smaller diameter than the rod you are using. Also, if you have a high power magnifier or microscope, you might take a look at the burr you are getting from that tool to see if it is a smooth, sharp edge or if it is rough and uneven.

JKJ