Negative Rake Scraper

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Goodland, Kansas
I have seen a lot of talk on other forums about negative rake scrapers and I have been thinking about it for a while. So I went to PSI and bought a 3/4" sqaure end scraper. I took and ground it to a combined angle of 42*. It looks like a skew. I had been in contact with Cindy Drozda who has been great in helping. Anyway once I got the shape I wanted and is one she suggested then you only sharpen on one side so you have a burr on the top side. I will say this. I have been working on another lidded box like the finial star. I used it on the inside of the lid and the top side of the lid. I can say it does a great job with thin, wispy ribbons and I actually finish sanded it with just 400 and 600 grit. Anyway the finish on the inside and outside was just smooth like glass. I also wanted it to try and lighten the dye like she does on the background colors. So will continue to try it on different projects to see how it goes.
 

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Bernie that is rather unusual grind. I may have to give that a try. I use a negative grind on some of my scrapers but I just use a diamond file and put a 10 or 15°bevel on the top and a regular scraper grind on bottom. I like how mine works, but may give your way a trial. Thanks for posting.
 
You are right Ted. They don't last long for sure but boy do they work nice. Fred I used this tonight to work on a chinaberry bowl that was giving me fits. It is kinda like elm. I just couldn't get it smooth with a gouge or shear scraping. So I mounted it up and in 3 passes it was done. I started sanding 220 and 320. Put my first coat of finish on and the inside now is smooth as glass. I am happy with the tool. I know it is not a cure all but it does have it's place in a turning arsenal.
 
That is great!
I really think it is all about having the right tool for the job, I know this means that sometimes you end up with a lot of tools, but I'd rather have a special tool to solve the problem then spend the farm on using more and more sandpaper!
 
Very nice tool! Another thing worth noting is that if it's honed to a mirror edge you don't necessarily need a burr, especially on really dense woods (like exotics). I used a radius-edged skew honed to a "carving tool" edge as a negative rake scraper on a recent project. It worked superbly even without a burr.

Hutch
 
Bernie thanks for the pics on how your shaped the scraper...Hutch thanks for telling me what to do with my skew that I've never even used! :thumb:
 
Your welcome Jeff. Hutch I did use a skew for a long time but I just got tired of honing and sharpening my expensive Lacer skew. I think Ken Fitzgerald and I are about the only one's that love skews.
 
Hey Bernie and all the rest of you really bright guys.

I understand that this 'negative rake scraper' seems to work really well but I have a lot of difficulty understanding the physics or engineering principalof it.

In my very small mind it would seem to me that all one does with a scraper is place the cutting edge against a spinning thingy. Again, logically at least to me, the only angle that I can understand is the angle that the edge is place against the spinning thingy.

So can any of you let me in on the logic that would explain the difference between a regular scraper and a scraper that is sharpened on both sides?

When I first saw Cindy using a scraper sharpened like this I said to myself, "self me things someone is pulling your leg and trying to get you to buy another toy for your lathe but now with all of you touting the benefits of this tool . . . .

This is probably a lot like golf. I play, or try to play a little and now I hear that if I want the ball to 'draw' (that is go a little left) I should aim right.
Likely the same logic, that my muddled brain can't comprehend.

Pete
 
Peter I can't explain the why it works but I watched Cindy use here scraper at a demo she was giving. Either the one I have shown here or a regular scraper with two bevels is a negative rake scraper. The tool is held level on the rest and not in a downward postion. The reason it is not grabby is because of the secondary bevel. Anyway the way it was explained to me was if you have a scraper say ground with a 70* bevel below and on the top you grind a say 5* to 7* bevel it is considered negative rake. Mine has a combined total bevel of 42*. I can tell you on these types of scrapers they do a marvlous job on hardwoods and exotics. The curlies are just light and fluffy. The surface as my granddad would say is smoother than a baby's bottom. I turn a lot of chinaberry, elm, willow and cottonwood since it is so abundant here. I have a devil of a time get these woods smooth no matter how sharp my tools are. The other day after cussing for two days before I made this scraper I finally got a chance to run it thru the bottom of a chinaberry bowl 2 or 3 times. I actually could start sanding around 220 grit. So hopefully someone else will jump in.
 
I made a negative rake scraper that resembles the Drozda NR scraper. It works but no better and in truth not as well as the same shape in a traditional scraper. In addition I don't think it is as versatile as a traditional scraper.

For instance when scraping the interior of a small bowl I can take a traditional scraper, as long as its curve is tighter than the curve of the bowl, and just pivot it from a starting point near the center and scrape the entire interior of the bowl. This is the method I learned from Richard Raffan and he uses scrapers to great effect on many projects. Recently he was making fun of NR scrapers and pointed out their lack of versatility. He did use his skew as a NR scraper for one little spot in a cross grain box.

I don't use a burr any more on a scraper. In fact I hone it off with a diamond hone. I am looking for that edge to be as sharp as a skew but with two planes meeting at a different angle. A skew would never have a burr intentionally. Raffan hones the two planes of his scrapers just like you would hone a skew. I have become increasingly convinced that properly used scrapers can significantly reduce your turning time and sanding time.

I know there are many who like NR scrapers but as my father-in-law said that is why they make chocolate and vanilla.
 
And Mike I like Chocolate.:rofl:

I understand what you are saying. I love my skews but I am not a fan of scrapers. Generally it is the other way around most people will use scrapers and will put their skews in a drawer.
 
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