scraper sharpness

[Charlie Knighton]

thanks to Alan Lacer and Jerry Wright for their article "Scraper Sharpness"

i have read it several times and had never considered honing any tools, mainly because i did not know how. i have a diamond hone but wonder which side to use, fine or course?????? do you use the same side fine or course for the top finish as the edge???????? do you use both the fine and course on each, top finish and edge?????? the photos were particularly good.

I liked this article and look forward to the gouges and skew chisels article.

 

[john lucas]

I have always done my skews with a medium diamond hone which is about 270 grit. I hone the top burr off and then raise a burr using that hone. After reading the article I'm going to try to polish the top with my ultra fine hone which is about 600 grit.
I've always wanted to build one of the burr raising tools like the Lee Valley one. It shouldn't be hard. You can shape the cone part by putting the piece of steel in the lathe and roughing it with a file and then polishing it with different grits of sandpaper. Then harden it but don't temper it. That should give you a very hard piece of steel.

 

[GLENN ROBERTS]

Charlie, you are right, it was a great article, thanks to them for going to so much trouble.
While we sometimes can go too deep into things, I think that its healthy to investigate some of the 'myths' that have evolved with woodturning. Like you, I want to see more, so we all might benefit.

Glenn

 

[Greg_Haugen]

This past August I spent a day with Alan at his place turning one on one. I'd HIGHLY recommend it. That day we made hook tools and worked with scrapers exactly the way it says in that article. Alan mentioned at one point about the article coming out in the near future. As far as grits go, medium is 250-300, fine is around 600 (commonly used by turners), and ultra fine is 1200 (used by carvers), depending on manufacturer of course. I've got a "fine" from woodcraft as well as a "fine" 600 grit from Alan. I like Alan's alot better. Having the radiused edges makes it very nice for gouges and hooks as well as having the "diamonds" on both flats gives a lot more surface area. As these are used "steel dust" does get down into the diamonds. They just need to be cleaned by being sprayed and wiped off with WD40. Alan also carries a handheld "burnisher" that's made by Hamlet, it's not expensive and works great. I also have one of the "screw to the workbench" versions. I like the hand held version the best. You can adjust everything about the burr, the size of it by the pressure applied and the angle of it by the pitch of the tool. Also it doesn't matter the size or thickness of the scraper, that does made with the other type.

We started with a freshly ground burr in a shear scraping angle on a piece of endgrain poplar. We then moved to a "heavy" burr raised by a burnished ofter the top was honed, then down to a "medium" burr, then a "fine" burr. It was amazing!! The burnished burrs outlast the "grinder" burr by a long shot. One tool can absolutely hog the waste out of the way and then with a simple adjustment of the burr can create the smoothest finished surface. Using the "honed and raised burrs" this way would be like using a "1/100" of an inch (probably less actually, I'm just guessing) Hunter tool. The tightest, tiniest curly shavings are produced. My "box turning" tools now consists of Hunter's #5 tool, a #3 swan neck tool, a 3/8" beading/parting tool that I've ground to a 3/8" round noce scraper (my finishing tool for the ultra fine surface with a raised burr) and a 1/2" wide a 3/8" thick scraper with a raised burr that I use in conjunction with the Hunter #5 to hog the waste. The two scrapers are just incredible with this technique.

Any questions about this technique, feel free to ask. It's one of the best techniques I have in my turning arsenal now.

 

[Malcolm Smith]

This past August I spent a day with Alan at his place turning one on one. I'd HIGHLY recommend it. That day we made hook tools and worked with scrapers exactly the way it says in that article. Alan mentioned at one point about the article coming out in the near future. As far as grits go, medium is 250-300, fine is around 600 (commonly used by turners), and ultra fine is 1200 (used by carvers), depending on manufacturer of course. I've got a "fine" from woodcraft as well as a "fine" 600 grit from Alan. I like Alan's alot better. Having the radiused edges makes it very nice for gouges and hooks as well as having the "diamonds" on both flats gives a lot more surface area. As these are used "steel dust" does get down into the diamonds. They just need to be cleaned by being sprayed and wiped off with WD40. Alan also carries a handheld "burnisher" that's made by Hamlet, it's not expensive and works great. I also have one of the "screw to the workbench" versions. I like the hand held version the best. You can adjust everything about the burr, the size of it by the pressure applied and the angle of it by the pitch of the tool. Also it doesn't matter the size or thickness of the scraper, that does made with the other type.

We started with a freshly ground burr in a shear scraping angle on a piece of endgrain poplar. We then moved to a "heavy" burr raised by a burnished ofter the top was honed, then down to a "medium" burr, then a "fine" burr. It was amazing!! The burnished burrs outlast the "grinder" burr by a long shot. One tool can absolutely hog the waste out of the way and then with a simple adjustment of the burr can create the smoothest finished surface. Using the "honed and raised burrs" this way would be like using a "1/100" of an inch (probably less actually, I'm just guessing) Hunter tool. The tightest, tiniest curly shavings are produced. My "box turning" tools now consists of Hunter's #5 tool, a #3 swan neck tool, a 3/8" beading/parting tool that I've ground to a 3/8" round noce scraper (my finishing tool for the ultra fine surface with a raised burr) and a 1/2" wide a 3/8" thick scraper with a raised burr that I use in conjunction with the Hunter #5 to hog the waste. The two scrapers are just incredible with this technique.

Any questions about this technique, feel free to ask. It's one of the best techniques I have in my turning arsenal now.

There are a lot of approaches to this and it somewhat depends on the tools one is using and the wood. Does one actually want a burr on the tool? With very hard wood, it won't last very long. I sharpen with a Tormek and use it to polish away any grinder marks, determining this with a good loup. This works well for me with very hard woods. A burr seems more workable with softer woods, at least to me. One should really try different sharpening methods with different tools always examining the edge to see what one has produced. Once one has settled on a single way of sharpening, a better method will not be found.

Malcolm Smith.

 

[Greg_Haugen]

The main issue on dense woods is that the burr would grab, self feed, and a catch will be the outcome. By honing off the burr the scraper would be less aggressive. However, a "burr-less" edge would not out last a properly burred edge. It just doesn't have the support of a burr. Stuart Batty uses the negative rake scraper with a grinder burr on it, which will last longer than a "honed" burr-less edge, as well as the highest level of steel he can find to hold the edge. Even at that it's seconds before it deteriorates. The key to dense woods is technique. Presenting the edge/burr to the wood in a 45 degree or more angle it lessens the risk of self feeding and also "Cuts" more than a flat out scrape. The more any edge cuts, the more it will outlast a scraping edge. When I turn lignum vitae, one of the densest woods in the world, I'll hollow it with a #5 Hunter tool at an angle-sheering cut rather than scrape or the 1/2" scraper held flat with a burr-less edge but the scraper requires a lot of trips to the grinder . And then I'll finish or "Fine tune" the surface (more so for contour or profile then for "finish") with the 3/8" square scraper with a "light" burr at an angle. 220-320 grit sand paper almost wrecks the surface.

Yes, on dense woods a scraper that will be "presented" flat will be "safer" without a burr than with it. By presenting it at a "sheering" angle with a burr- it's safe and creates a nice finish. There are so many more options once someone learns to use scrapers at a sheering angle as well as flat. Along with the level of burr from a burr-less edge to a "large" burr to hog out waste flat or at a sheering angle.

That's one thing that's so unique about scrapers, they're limitless in the options they can be used.

 

[rsser]

Two pro turners I've heard recommend not using a burr on dense timbers nor on soft ones.

I've assumed that, as the burr is really just a saw-tooth like edge, the tips would chip out dense wood, and pull out soft wood fibres.

Haven't yet read the article but have compared the burr off a 60 grit dry grinder and the hook turned by the Veritas burnisher. At 60x magnification, there's not much difference between the two. The burnished edge is slightly smoother. Maybe that's just my technique.

Looking forward to reading the article.

 

[MichaelMouse]

Two pro turners I've heard recommend not using a burr on dense timbers nor on soft ones.

I've assumed that, as the burr is really just a saw-tooth like edge, the tips would chip out dense wood, and pull out soft wood fibres.

That's not true of a turned burr, only a grinding burr. The burr you turn is as smooth as the edge you turned it from. If you honed off your bevel and face to 220, you turn a 220 burr, more or less. It becomes a fine blade when held properly, cutting the fibers even when presented nearly perpendicular to the rotation. Sort of like a mini version of your Hunter tool. If you don't "ticket" or turn the burr, you have an edge like any other tool, which cuts fine with high rates of shear.

Problem is, rather than turning at 30 rpm and taking the finest cuts, we spin that puppy up so that minor problems in the wood bend/break the edge unequally. The flat folks work at hand speed and tend to roll it back uniformly. Of course they can burnish down and turn again a couple times before the cracks catch up with them. Difference is the malleability of the steel they use for scrapers.

 

[rsser]

The burr you turn is as smooth as the edge you turned it from.

Well, that's what I was expecting but the images at 60x didn't really bear it out. Will dig them out and post them later.

 

[rsser]

OK, well there's more difference than I recall though the turned up hook is still not esp smooth.

Pic 1 is burnished with a Veritas unit.
Pic 2 is dry ground at 60 grit.

To get an idea of scale, you can see the bevel in Pic 2 and it's a quarter inch thick.

 

[Greg_Haugen]

First of all, great pictures!!! Very nice!!

As it shows, my opinion which along with $5 would get you a cup of coffee at Starbucks, I think it's considerably better with the Veritas burr. At least the way I'm looking at it.

One question, was the top of the scraper honed flat before the burr was raised?

When I was with Alan he worked for about 20 minutes to "tune up" my scraper. I had "milling" marks still on the top. He wanted those off. The top of it was "polished" with a diamond hone. After using that one polished and then another. It was obvious in the difference. Or else those milling marks would end up being raised with the burr. Honing the top of a scraper after its ground will do both jobs, remove the grinder burr but also keep the top of the tool really keen.

Great pictures again!

 

[MichaelMouse]

One question, was the top of the scraper honed flat before the burr was raised?

Yep, can't make half an edge and expect full results. As I said above, face and bevel before ticketing.

Ern, goes back to the roughing gouge discussion. With those mill marks inside, you'll always have a notch in the edge, which is why it was unacceptable. I do my cabinet scrapers on a hard Arkansas stone, because the edge produced by working on my medium India scratches my fingernail rather than shaves it.

 

[rsser]

Thanks Greg.

Yep, the top was flattened on a diamond stone, then the edge was swept against the burnisher four times. What I did not do was dress the existing dry ground bevel on a diamond stone or fine wet grinder. It's reasonable to assume that a smoother hook would have resulted had this been done.

The Lacer and Wright article is timely.

I'm embarking on scraper edge durability tests with 3 treatments: dry ground burr, a burr or hook turned with a burnisher, and bevel and top honed. Just need to source enough consistent grained hardwood for spindle blanks.

As a by the way, the old tip of jamming a burr-edge tool into hardwood to remove the burr did not work in my tests, at least not with a scraper.

 

[robo hippy]

As some one who uses scrapers extensivly in my roughing and some finishing cuts on bowls, I found the article interesting. I was left wondering about the 60 grit wheel for sharpening. I use an 80 grit CBN (cubic boric nitride) wheel which leaves a finer grind than a normal 80 grit wheel. It raises a nice burr, and I have found that one to be better for cutting than a honed no burr edge or one I turn with a burnisher. I haven't tried the hone raised burr yet, but have always polished the top of the scraper before raising the burr. I would expect the honed burr to be better suited for a finish cut, rather than a roughing cut. Just not tough enough.

Food for thought.

robo hippy

 

[rsser]

Yes, I'm a bit puzzled as to why they didn't vary the bevel treatment. Of course, for each change you double the number of tests needed, but still, an edge consisting of one intersecting face that's pretty rough ....