Negative Rake Scraper

[Bernie Weishapl]

I have a couple of scrapers that I would like to make a negative rake scraper out of. One is 3/4" the other is a 1/2". Is there anywhere that shows how to shape and sharpen these? I used one and forgot to look at the profile plus the angle of the bevel. All I know when doing the lidded box it took light fluffy curlies and we started sanding at 320 or 400. I know it was pretty fine grit.

[Steve Schlumpf]

Bernie, check out these two sites. Hope it is what you are looking for.

http://www.woodturningdesign.com/askdale/8/8.shtml

http://www.hiltonhandcraft.com/Articles/The%20Negative%20Rake%20Scraper.pdf

[Ron Ainge]

Bernie

As you know I am at the Utah Woodturning Symposium this week and I just took a tool class last night for the factory rep from Sorby tools and it was his opinion that a Skew is one of the better negative rake scrapers there is. I have use my skews that way for years and never thought anything about it until last night.

I don't think that there is any difference in the angle of the grind you would do on a scraper to make if negative. Most of the guys I know do a secomd grind on the heal of the scraper so that it does not contact so much wood and that makes it a negative rake scrakper.

[Bernie Weishapl]

Steve, Ron and Gordon thank you for the info. I have been doing some research as well. I think I will stick to my skew for a NRS. I appreciate the info.

[Paul Engle]

Bernie any where from 7 to 12 degess from the edge back, I have two, one at 7 and one at 12 with the 12 being less agressive. they are round nose , the one Tim Yoder uses is a bowl scraper, it is ground across the nose and along the left side about 2 inchs back from the nose in about 3/8" inch. Also found on Craft supplyes WT's cat called a hard wood scraper page 12 or so ...you can see the angle quite well .it is round nose.

[Pete Jordan]

Bernie,

I have Eli Aversari's tool that Stu recommended. I will take pics when I get home. I sharpen it upside down.

[Reed Gray]

The first time I saw one in use was at a Stewart Batty demo. I finally made one as I like scrapers. I grind the top bevel at about 45 degrees, and the bottom bevel the same as my other scrapers, which is pretty blunt, in the 75 to 80 degree range. A negative rake scraper doesn't work on softer woods at all, but on really dense harder woods, it does wonders. I get better results with a shear scraper on Big leaf maple. On Madrone, and the Mountain Mahogany, I get better results with the negative rake scraper. It isn't for any stock removal, just touch up work.
robo hippy

[Curt Fuller]

I might be completely wrong here but my understanding of negative rake scraping is basically using a skew as a scraper. A skew is sharpened on an angle, that's were it gets its name, and it's meant to be used as a cutting tool held with the cutting edge at an angle to the wood it's peeling off and riding the bevel of the grind. But if you lay a skew flat on its side and scrape with it, you're negative rake scraping, I think. To make a negative rake scraper you would grind it similar to a skew as far as the sharpening angle is concerned, but you grind it square for a tool to do the square bottom of a box. I might be over simplifiying it, but that's how I've always understood it.

[Pete Jordan]

These are the pictures that I promised. I can't remember who I ordered it from but it took 2 months to get it because they don't keep it in stock. It works great!

[Bernie Weishapl]

Thanks everyone. That info helps a lot.

Thanks for the pictures Pete.

Curt that is what I have been using was a skew as a NRS. I just watched Cindy Drozda use a NRS on cherry and it just was smooth as silk. She started sanding at 400 grit.

[Nick Stagg]

Stuart Batty described the whole procedure in the AAW magazine some time ago. I don't remember which issue it was, I'm sure someone will remember.
While you can take light cuts with a skew flat on the rest, it's probably not the best tool for the job, especially if you want to use it as it was intended. It's the burr on the tool that you raise that does the work, and on M2 steel it doesn't last long. So when sharpening, just apply one edge to the grinder

My negative rake scrapers are made from 10V and the burr I use is raised on a 36 grit wheel. I grind them in a slight arc so I can use different parts of the edge to preserve the burr as long as possible. When the burr is gone, don't continue as all you'll do is reverse what you've accomplished. Go back to the grinder!
Nick

[Dave Rudy]

But if you lay a skew flat on its side and scrape with it, you're negative rake scraping, I think.

Almost. The "skewness" os the skew has nothing to do with negative rake scraping. You could grind the skew square across the front, then re-sharpen without the skew angle and have a negative rake scraper.

What makes a negative rake scraper is sharpening on both sides of the cutting edge (scrapers are only sharpened on one) and then finish sharpening on only one edge to produce a burr on the other.

That's why a skew makes an ideal negative rake scraper. You need not reshape the tool; just produce a burr. When you want to use the skew as a skew again, just remove the burr (or resharpen the tool).

When using a skew as a negative rake scraper, the attitude should be like a scraper -- pointing down or no more than horizontal, unlike using a skew.

Hope this helps.

Dave

[Bernie Weishapl]

Thanks again for all the info. I appreciate it.

[Burt Alcantara]

Bernie,
I have one of these and it works very well. Not sure if it's what you are looking for.
http://www.robert-sorby.co.uk/ Select "Latest Products - Hardwood Scraper"

Burt