Bevel on scraper

[Bill O'Conner]

what is a good bevel for a scraper just took an old skew and made a round scraper out of it

Thanks
Bill

[Mike Lipke]

Isn't 30 deg. the standard number?

[Jim Underwood]

30 degrees from which side?

Or is that 70 degrees?:D

[Bernie Weishapl]

I use 80* on mine.

[Mike Lipke]

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[Brian Novotny]

I like a good, steep, 45 degrees on mine.

[Richard Madison]

I don't use scrapers as such, but my tool bits are all ground at about 75 degrees included angle. Many people define the bevel or grind angle as the included angle at any point of the cutting edge, measured in a plane perpendicular to a line tangent to the cutting edge at that point.

[Reed Gray]

I don't know my angle, but I am guessing around 70 degrees or so, fairly blunt. 45 is too steep for me, and too dainty for me. I use them mostly for roughing out bowls, and for shear cuts.
robo hippy

[Jim Underwood]

So 45 degrees is too small for you Reed?:rolleyes:

Heck, this week I was looking at a turning book that was published in the '70s (by a very well known turner), which gave an included angle of 35 degrees on a scraper. I was dumbfounded.

Most books I see that specify an angle or a range are well up into the 70-80 degree area.

[Dave Schell]

Does the angle of scraper really matter? Bevels don't rub when scraping so I'm wondering why the angle would even matter? Would some angles hold an edge longer than others? Beats me.

[Kyle Iwamoto]

Does the angle of scraper really matter? Bevels don't rub when scraping so I'm wondering why the angle would even matter? Would some angles hold an edge longer than others? Beats me.

That's what I'm thinking. Aren't you supposed to use the scraper with the tool rest high so the scraper is pointing down at center? That means (to me) the angle does not matter..... Or am I completely off base and using the scraper wrong?

I'm SO confused......

[Reed Gray]

I think the more blunt angles will hold up better for the heavy bowl roughing work. It does work excellently for shear cuts as well (bevel does not rub in either situation).Exactly why people use sharper angles is unknown to me. There was a branch of the Chippendale School of Woodworking here in Eugene for a year or so, and they had some Brittish turners visit, and they had the 45 to 35 degree scrapers which was all they used on their bowls. Maybe it is another thing for me to experiment with. I have used a skewchigouge once at a Allen and Stewart Batty workshop, and it is ground to a 35 degree or so angle. Great for rolling beads and coves. It is smaller, like 1/2 inch, not like my big scrapers. You can ride the bevel on a scraper, and you can scrape, and shear cut. Hmmmmm. I may have to regrind another tool.

robo hippy

[Wally Dickerman]

There are two ways to measure the grind angle. 60 deg. measured one way is the same as 30 degrees the other way. We seem to use both ways with turning tools, which can be confusing. I grind a 60 deg. nose on most of my bowl gouges and a 30 deg grind on my scrapers. Actually, they are the same angle.

I have done some experimenting with scraper grinds and have settled on 30 deg for most of them. I usually use my scrapers with a light touch for refining a form or for shear scraping. Seems to cut better than a more blunt angle. Any steeper becomes too fragile.

wally

[curtis rosche]

it depends on what you like. and the wood you are turning try different angles and see what you like

[Dan Forman]

Not sure of the physics behind it, but angle does matter. A more acute angle not only cuts more aggressively, but also more cleanly, with less tear out. The usual case of diminishing returns applies here.

Dan

[Jim Underwood]

With a scraper, I believe it's the burr on the edge which actually does the cutting. In practice it doesn't last very long, so you must renew the burr quite often. Since the burr is the cutting edge a scraper is presented in a trailing (scraping) manner rather than a leading (cutting) manner. Skews and gouges cut, scrapers, well.... scrape. When you are presenting the scraper correctly in trailing mode (handle higher then the cutting edge) then the bevel of the burr is actually supporting the cut.

Think of a cabinet scraper versus a hand plane and you'll get the idea.

I don't know that the angle matters so much as the burr you create. However, I've heard that the larger included angles help dissipate heat so that the edge isn't worn away so quickly. If you use a smaller angle like 35 or 45 degrees then the burr probably disappears just that much sooner. If you use a gouge or skew like a scraper, you can pretty much guarantee you'll have to sharpen it before you can actually cut with it after that.

[Bob Bergstrom]

Here's a good explanation of a converted skew into a shear scrapper by Dick Sing at the Windy City Woodturners meeting in July. It is a different approach with fantastic results. http://www.youtube.com/watch?v=kLLTV8bJkfQ

[Richard Madison]

Impossible for me to tell from the video what the tool shape was. Looked like he was just using a curved skew as a scraper. I converted a skew to a scraper once, and have since converted it back to a skew.

[Wally Dickerman]

Here's a good explanation of a converted skew into a shear scrapper by Dick Sing at the Windy City Woodturners meeting in July. It is a different approach with fantastic results. http://www.youtube.com/watch?v=kLLTV8bJkfQ

It's called a negative rake scraper. It's used on very hard woods or on acrylic plastics for a near perfect surface. It's used with a very light touch for best results. Doesn't work vey well on soft woods.

Stuart Batty uses a NR scraper on hard and difficult woods where other scrapers just wouldn't do a good job.

Wally

[Bob Bergstrom]

Very well said Wally. Dick has a fantastic touch. The bowl he is scrapping is cherry. His approach to the wood takes skill and experience. He developed this shear scrapping technique doing inlays on jar lids that were of many different woods ranging from maple, cherry, and walnut to exotics.

[Reed Gray]

Jim,
I think I will disagree with you a bit. Some scrapers are used with a burr, my preferred method, and some are used with the burr honed off. Any cutting tool with an edge can do a scraping cut, or a shear cut, and can also cut with the bevel rubbing or not rubbing. Held flat on the tool rest, a scraper does the best scraping cut of any tool out there. Lots of mass, very stable. You can do the same cut with a gouge, simply have the flutes on their side, and you are scraping. Take the scraper and have it at a 45 degree angle on the tool rest, and it is doing a nice shear cut. This is a finish cut for clean up work, not stock removal, just like when you shear cut with a gouge, only you don't have to drop the handle. You can get just as nice of a finish as you can with a shear cut on a gouge. It is the same steel, and sharpened the same way. The difference is in the angle the tool is presented to the wood's rotation. The burrs on my scrapers last just as long as the edge on a gouge. I do not burnish a burr on mine, I remove the old burr first on a diamond stone, then grind a fresh on. I do push the scraper into the grinding wheel, rather than just kiss the surface.

robo hippy

[Jim Underwood]

Reed,
It's quite alright if you disagree, because maybe I'll learn something. Wish I could visit your shop and see what you're talking about.
Most of what I know about scrapers is what I've read. I've not actually gotten a good finish cut out of my scrapers so far. (Yeah yeah, I know, I should shut up if I don't know what I'm talking about. :rolleyes:) I've watched people do it before, but I just can't seem to get a good burr on one... I'm wondering if I should get one of those burnishing tools. Perhaps my 100 grit wheel isn't aggressive enough?

[Reed Gray]

Jim,
I started playing with scrapers out of curiosity. When I first started turning, I was told to use a scraper only if I absolutly had to. Well, I started to wonder how people could turn bowls using only scrapers. So I started playing around. It was interesting, and lead me to the practice of using scrapers for my bowl roughing and clean up. Some times the gouge cut is great, and some times it is only okay. With the scrapers, I can almost always start sanding with 120 or higher. Mike Mahoney says that he always starts sanding with 80 grit. For me, that is decided by which would take longer, sanding out the 80 grit scratches with 120, or sanding out tool marks with 120. When using only gouges, most of the time it was 80 grit. Rounding off the bottom bevel of the gouge helped lower that number, and the scrapers for shear cuts on both the inside and outsides of the bowls lowered that number more.

I do love having people in my shop as a mentor. That is as much fun as turning. I am doing several local bowl turning demos in preparation for doing a bowl turning DVD. I do some things differently. Hopefully in about another year.

robo hippy

[Wally Dickerman]

Reed,
It's quite alright if you disagree, because maybe I'll learn something. Wish I could visit your shop and see what you're talking about.
Most of what I know about scrapers is what I've read. I've not actually gotten a good finish cut out of my scrapers so far. (Yeah yeah, I know, I should shut up if I don't know what I'm talking about. :rolleyes:) I've watched people do it before, but I just can't seem to get a good burr on one... I'm wondering if I should get one of those burnishing tools. Perhaps my 100 grit wheel isn't aggressive enough?

I've used scrapers since the dark ages. Except for NR scrapers I don't pay much attention to the burr on a scraper. I started turning bowls back in the 50's. It would be 30 years before the bowl gouge and HS steel would show up. There weren't any bowl hollowing tools available so I made my own. I used a 1 inch forged spindle gouge for part of it. (very grabby). Most of was done with scrapers. My favorite was a 1/2 x 1/2 inch very hard piece of steel about 18 inches long. I installed a handle and found that I could really hog off wood with it. No burr involved. Guess what...I still use same tool or one just like it today for hollowing the bottom part of my hollow forms. With the handle tucked into my side and under my forearm I can really remove wood and I get shavings. I grind it at a 30 degree angle and it's side ground.

I use a tantung steel scraper on my Stewart tool for finish scraping in a HF and it has no burr. Tantung steel, if you don't know, is very hard and holds an edge for a long time. It's between carbide and HS steel in hardness. I can grind an edge but can't touch it with a drill.

IMO, the folks that say you shouldn't use anything but a gouge for bowl turning don't realize what can be done with a scraper properly used. On some of the very hard exotics I can get a mirror finish when using a scraper and I hone off the burr, though it must be sharp.

Wally

[Reed Gray]

Wally,
The Oregon coastal turners have used a tantung scraper for turning their myrtle wood bowls since the 60s or 70s. It is called the 'Big Ugly' tool. 3/4 inch by 30 inch square bar stock, with a 7/8 inch wide piece of tantung silver soldered onto each end. You wear a heavy leather glove on your 'handle' hand. I have a civilized model with a wood handle, and use it for difficult woods. I could see having more of them in different shapes. It is the forrunner of the Easy Rougher tool. They do prefer a burr on theirs. Gets as sharp as the micro grained carbide, and almost as hard.
robo hippy

[terry richards]

The best tool for the job is the one that works best for the person doing the job.

If you hold the scraper handle above the center line with the cutting edge level or below, you are scraping. If you hold the scraper handle below the tool rest with the cutting edge above and rotated toward the direction of the cut travel, you can then appease the scraperphobians by calling it a "flat topped gouge."

All my scrapers are ground at 50-55 deg (top plate angle). I don't worry much about the burr, since it goes away in seconds, once you start cutting.

And, yes, I do use gouges as well where they work best.