Creating/Sharpening Negative Rake Scraper

[Edward Weingarden]

I tried converting what was a "conventional" scraper into a NRS. I ground a bevel on the top surface and then flipped it over to grind the lower bevel and create the burr. When I went to use it, there was barely a spec of dust coming off of the piece. It was like I was putting a blunt object against the wood. Can someone tell me the correct way to grind a non-NRS into a NRS. Thanks.

[Thomas Wilson80]

What are your top and bottom angles?

[John K Jordan]

I tried converting what was a "conventional" scraper into a NRS. I ground a bevel on the top surface and then flipped it over to grind the lower bevel and create the burr. When I went to use it, there was barely a spec of dust coming off of the piece. It was like I was putting a blunt object against the wood. Can someone tell me the correct way to grind a non-NRS into a NRS. Thanks.

If you have a significant burr on the upper side and are holding the scraper horizontal on the rest, it should cut well. (Make sure you can feel the burr when sliding your finger down the top bevel.)

I think my favorite NRS are ground to about a 60-deg included angle, a bit like grinding a skew chisel. I grind the same bevel on both sides on these so I can flip them over and use them either way (after changing the burr, of course.)

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I use three different ways to create the burr.
1) After resharpening, I use the burr from the grinding wheel. (I sharpen on a 600 grit CBN wheel.)
2) When that burr quits cutting I hone it off (x-fine diamond hone) and use a carbide burnishing rod to raise another burr. This lasts longer than the grinder burr.
3) When I want to make extra fine "cuts" I hone the burr off and raise a very tiny burr with the extra-fine diamond hone by honing firmly on the bottom bevel. This makes incredibly fine shavings on most types of wood.

This is the carbide burnisher I use:

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I don't grind all of my negative rake scrapers with the 60-deg angle. Some of the smaller scrapers are more like 80+ deg. However, I use these primarily on end grain, such as box lids, etc. They leave a glass-like surface on hard, fine-grained wood such as ebony, dogwood, and cocobolo. On these I usually hone and polish/strop the bevels a bit after sharpening and use a burnished burr.

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JKJ

[Reed Gray]

I think I touch on it in my sharpening video, but still need to do a video just on the NRS. Main thing for using the grinder burr is that you sharpen the top side, the one you will be cutting with first, then sharpen the bottom second so you raise the burr on the first side. There is an interesting video by Eric Loffstrom and Jimmie Allen of Boxmaster Tools who will be taking over D Way tools from Dave Schweitzer in January. They use a 70/30 or so grind, and sharpen the bottom bevel up side down, so at about minus 20 degrees. I will see if I can find that link.

Here it is... it is a commercial kind of, but shows a lot of technique...

https://www.youtube.com/watch?v=YsatMuK1Ei8&t=7s

robo hippy

[Edward Weingarden]

John:
From the looks of your scrapers in photo #1, I think my included angle is too large. Each surface is probably ground to around 60 degrees.

Reed - thanks for the link but there's no video there at this time.

[John K Jordan]

John:
From the looks of your scrapers in photo #1, I think my included angle is too large. Each surface is probably ground to around 60 degrees.
Reed - thanks for the link but there's no video there at this time.

I've heard people say that a NRS won't work unless the included angle is less than 90-deg. I haven't tested that myself, although I have measured a couple of the smaller ones I use for end grain as 89-deg.

JKJ

[Reed Gray]

Hmm, the link was there for me... No clue here...

As for NRS not working if included angles are greater than 90 degrees, not true. Sorby makes one that is an 80/20 or there about. It is more difficult to make a raised burr on it, but it can be done. I prefer about a 60/30 for burnishing a burr. Grinder burrs seem to work fine at most angles. The steeper the bottom angles, the more sturdy the burr is, probably because there is more metal under it to support the burr. The 30/30 skew chisel types the burr is very fragile. Eric and Jimmie like about a 70/25 or 30. If the video link works for you, you can see what they do.

robo hippy

[Bill Blasic]

Reed the link you put there works but it takes awhile to come uo, perhaps he did not wait long enough.

[JohnC Lucas]

On my tools I find an included angle of less than 90 works better for raising a burr. Might just be my tools or maybe my technique. I ground my negative rake scrapers so the angle is the same on both sides. They look like a skew. When the burr wears off I simply flip the tool and grind a new burr. This is very fast. Learned that from Stewart Batty. I will say that on some of my scrapers that aren't negative rake I find that I have to raise the burr with a steel instead of on the grinder. Again it may just be the steel or possibly the hardness of the steel in that particular tool.

[Pat Scott]

Edward I set my Robo Rest at 30 degrees and grind each side equally, this gives me an included angle of 60 degrees. I used to grind 35 degrees on each side which also works. As an FYI, Glenn Lucas grinds his NRS 33 degrees (66 included) because he has a gauge that measures that angle.

[Randy Hogan]

Very informative video from Robo's link. I'd like a recommendation on the brand of the correct burnishing rod for use on a HSS neg rake scraper. Thanks.

[John K Jordan]

Very informative video from Robo's link. I'd like a recommendation on the brand of the correct burnishing rod for use on a HSS neg rake scraper. Thanks.

Randy, I've used everything from the shaft of a spindle or bowl gouge to a couple of round carbide rods. All worked fine, as well as does a screwdriver or an allen wrench or some other piece of steel, the more hardened the better. Some people swear by a triangular burnisher which are readily available.

For years I used a 1/4" diameter rod but more recently switched to a smaller diameter rod (both far cheaper than buying a ready-made burnisher). The larger rod worked fine but the smaller rod takes less force to burnish the same burr. (BTW, this is sometimes called "ticketing" in texts I have from over 60 years ago.)

I posted this photo before of a burnishing rod I glued into a small handle, but here is another showing the larger rod:

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I already gave away the larger spare rod. I have a couple of spare smaller ones left if you want one - send an email (through the PM system here) with your address. Since I'm elderly and feeble-minded you might have to nag, er, remind me if you don't get it right away.

JKJ

[Edward Weingarden]

Thanks for all the feedback. I'll go back to the grinder and establish a smaller included angle.

Reed - the video came up for me this evening; very informative.

[Reed Gray]

I was out in the shop doing some organizing after the move, and found a 1/2 inch wide Little Ugly tool where the tip was a bit wide for the shaft, and a little tipsy. So, I turned it into a NRS. I tried a 600 grit burr first, and got almost glass smooth on some end grain fir. Tried it on some sugar maple and got the same results. Tried a side cut and got a good surface, but got a better surface with a shear scrape with the burr on the NRS....

Hmmmmm......

robo hippy

[Brian Deakin]

Please see link belows

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

and

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

regards Brian

[Pat Scott]

There is an interesting video by Eric Loffstrom and Jimmie Allen of Boxmaster Tools who will be taking over D Way tools from Dave Schweitzer in January.

What? Is Dave retiring and selling D-Way? What's going to happen to Dave's product line?

[Ralph Lindberg]

What? Is Dave retiring and selling D-Way? What's going to happen to Dave's product line?

Basically nothing.
Dave is retiring and Jimmie is a very good friend of Dave. Dave mentored Jimmie thru starting his BoxMaster line of tools. My understanding is Dave approached Jimmie about buying the business. If anything the fit and finish will go up as, well, Jimmie is even more ah, anal, about quality then Dave is (full disclosure, both are friends close enough we go out to dinner with both of them and their wives, Ellen works in Jimmie's booth and had her beaded vessels on display in Dave's booth, to help show what Dave's beading tools do)

Dave is in his 70's and both his and Lou's health is not what it once was. Jimmie's wife Cindy will be retiring soon and will handle most of the business end of things (Cindy is an IT geek for the Navy)

[Reed Gray]

Jimmie got baited and trapped.....According to him, he wanted a special grind and Dave made him an offer of "buy 20 and get them for half price, which means if you sell 10, you get them free...." or some thing like that..... The Devil made me do it the first time, the second time I did it on my own...... Dave will be demonstrating at the Oregon Woodturning Symposium in March...

robo hippy

[Jay Mullins]

I think I touch on it in my sharpening video, but still need to do a video just on the NRS. Main thing for using the grinder burr is that you sharpen the top side, the one you will be cutting with first, then sharpen the bottom second so you raise the burr on the first side. There is an interesting video by Eric Loffstrom and Jimmie Allen of Boxmaster Tools who will be taking over D Way tools from Dave Schweitzer in January. They use a 70/30 or so grind, and sharpen the bottom bevel up side down, so at about minus 20 degrees. I will see if I can find that link.

Here it is... it is a commercial kind of, but shows a lot of technique...

https://www.youtube.com/watch?v=YsatMuK1Ei8&t=7s

robo hippy
Robo, I watched the video from the youtube mentioned in your post. I bought one................I was amazed at how smooth the cut was. This was money well spent. Thanks for your contribution on this thread. JayMullins

[Alex Zeller]

I'm pretty good at judging angles but I bought one of those cheap Home Depot (General) digital angle finders. They are accurate to .3 degrees. I haven't tried it on a scraper to see if it would work but it should. It certainly would help those who are not an expert make repeatable grinds once you figure out what works for you.

[John K Jordan]

I'm pretty good at judging angles but I bought one of those cheap Home Depot (General) digital angle finders. They are accurate to .3 degrees. I haven't tried it on a scraper to see if it would work but it should. It certainly would help those who are not an expert make repeatable grinds once you figure out what works for you.

I make plastic things for various angles to set the platform as I want it.

This pictures shows some on the left and using the top one to set the grinder to sharpen hand scrapers at 90 deg. I use the right half of the bottom one for my curved negative rake scrapers.

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JKJ