Accu-Burr Burnisher

[D_W]

I've got some AEB-L that will have very high toughness at 58-ish hardness.

Not that it's a direct result of anything said here, but I'm inclined to see how it turns out as a scraper.

I don't think there's any real advantage to it over a typical 1095 scraper with a hardened steel rod (like hock's or any polished rod that won't damage a burr), but I'm curious.

I mention AEB-L because it's multiples tougher than 1095 and will roll a neat burr and hold it at a higher hardness, and despite being stainless, it's actually finer grained than 1095. the practical limiting factor is that for actual regular use, anything that's pushing the limits of files becomes impractical as the real impediment for almost everyone when setting up a scraper (at least that I've seen in person) is inability to quickly and repeatably get a neat fresh surface ready for rolling. After that, it's only a matter of doing a better and better job getting there faster and at the same time, with a nicer burr and understanding manipulating it so that the surface can pass for being planed if needed.

I recall Bill T mentioning at one point that he was dazzled by (name escapes me) a specialist who made plane inserts rolling a neat burr and showing that it would hold up for a long time. And puzzled at the insistence of the presenter to keep anything built up off of the face of the scraper when re-drawing or just re-rolling the burr.

It's certainly the case that at least for scraping to finish or perhaps only light sanding to follow that you can easily deform edges with trash left on them.

One of the easiest ways to find just how much wood can bend edges is to clog a plane with a poor fitting cap iron. The build up at the mouth of the plane if that's allowed and insistence on trying to push through it will obliterate the last bit of an edge - the important part that enters the cut.

But your comment earlier is right, of course. separating hardness between the burnisher and card or steel scrap is necessary. if one has polished carbide in hand, it's possible to roll a burr on fully hardened high speed steel. I scraped my floors this summer because they were shellacked before carpet was ever installed when the house was new, and the only practical thing to do was scrape them (the fastest thing). I was able to scrape about 700 SF of floor in a day. The iron is from a batch that Bill T and I had tested both for composition and hardness. they're by perception all the same. The one bill has and kept tested at 65.5 hardness, and they're *almost* m2 steel by composition. I could roll a polished burr on the iron with a carbide steel, though there's a limit to how big you could make the burr before it would get damaged (thus the thought about AEB-L - it'll be tough enough to roll, and I can keep it far enough off of file hardness that it can still be filed).

None of this is really necessary - I ended up sharpening the plane iron scraper with worn 80 grit sandpaper because it takes so much damage so fast on a floor that a burr is hopeless. the sandpaper will deflect the edge at the same time that it's wearing off the damaged tip - so good enough. the real key with scrapers has far more to do with getting the scraper in good shape as fast as possible (without compromising quality) so that one is inclined to do it, and then not getting married to the idea of getting every last little bit of shaving out of the scraper or continuing on when you feel the burr is ratty (scratchy feeling) as the burnisher goes over it.

I couldn't find any improvement with carbide on a 50-ish hardness 1095 scraper, but wouldn't have dreamed of touching the polished O1 rod on the higher-hardness HSS iron.

Getting really good at a scraper is a gateway drug of sorts to being able to use complex shape scrapers. All of woodworking and making things is sort of a gateway drug to the next harder thing.

 

[D_W]

Actually, I accidentally lied - one of the two irons is actually harder than 65.5 - the one on this "scraper cart". it made an ideal candidate for this because something went wrong in heat treat and it behaves like it's untempered. It's extremely slow on any fine honing, even diamond, and it chips easily - a bear of a thing to begin to even attempt to flatten the back on.

but use the sandpaper to maintain a steeper bevel to cover up the chipping, and use something coarse to get around the fact that it's almost too hard to hone with any normal abrasive, and it worked great.



one of the "green" ones from the original batch on a long handled scraper made to address edges. I later found out that with the end of the handle burnished at the tip, it could also slide over the floor and be used like the sled. The green one is from the batch that was tested - before sending it to bill, I mentioned that I didn't think it would be M2 because it would hardly hold a burr honing - that turned out to be because of the near 66 hardness. Spec from the listing was 61. it's actually a better iron to use at the higher hardness. both are the steel iron type with the brazed bit.

It still draws shavings of sorts, even "honed" to a burr with 80 grit paper on a board. it became every evident that it was far faster and more productive to hone the thing right away as soon as you have to bear down on it at all to get it in the cut. The same is true for sharpening plane irons - as soon as you become the downforce instead of the plane and regular use, you can continue on, but it's false economy.

 

[D_W]

I erred after this in going through a mostly full-run up of sandpaper. one finely set scraper after this actually left a much better uniform surface than 220 grit on an orbital floor sander. the floor sanding took at least as long as a second fine scraping would've taken, but i didn't know that ahead of time - far far more dust, too. even fine scraping and then just running 220 grit would've been better.

The key in this case being devising scraping tools that could be refreshed in a matter of 15 seconds and making them so that you could sit and operate the tool rather than stand over them and spend 90% of your energy holding your body up.

 

[Tony Zaffuto]

David,

Maybe 15 or 20 years ago, on the OldTools list, I mentioned that I had discarded very highly polished carbide core pins, that I would mail out to whoever wanted one. I mailed out well over a hundred pieces, including Derek C., (member here) and David Charlesworth (now deceased). David C. liked the carbide so much he asked if I could send some more for his class, which I did.

This carbide was so polished, it looked like a mirror, and the high grade was so smooth, it felt lubricated, though it was dry.

If I can find a piece or two, I’ll PM you and send you a piece. What some of us found was smaller diameters worked better.

 

[D_W]

David,

Maybe 15 or 20 years ago, on the OldTools list, I mentioned that I had discarded very highly polished carbide core pins, that I would mail out to whoever wanted one. I mailed out well over a hundred pieces, including Derek C., (member here) and David Charlesworth (now deceased). David C. liked the carbide so much he asked if I could send some more for his class, which I did.

This carbide was so polished, it looked like a mirror, and the high grade was so smooth, it felt lubricated, though it was dry.

If I can find a piece or two, I’ll PM you and send you a piece. What some of us found was smaller diameters worked better.

Smaller diameters allow less pressure to get the same burr, for sure.

I have a couple of carbide burrs, but they are mostly polished when you get them. I load a buffing wheel with diamond to bring them up.

I guess i've developed a preference with scrapers for a rod around 3/8ths inch, but it wouldn't really matter it the diameter was less if the edge is in good shape before.

the only issue I have with the rods is that they're often short, and I'd love a bigger diameter. At some point, if they get too long, I'm sure a drop of a burnisher would result in a broken rod.

i've noticed the same thing with the slickness on the polished rod bits (after bringing them to mirror with diamonds). there must be something going on with carbon steel and burnishers without oil where there's adhesion or something, and with carbide being ...well, high volume of carbides and high hardness, it doesn't occur or doesn't occurs as much and there's little resistance.

I was a little skeptical of much going on with woodworking tools or knives and adhesion until seeing pictures from the "science of sharp" with ceramic steels and knife edges. there's definitely a possibility that burnishing moves steel more than we think it does and maybe not just by "pushing" it.

too, I like to use card scrapers on knives to clean off stray glue, etc, from handles. if a knife is well made, it won't be touched or marked at all by a 1095 scraper.

this knife is AEB-L (think stainless 1070 more or less, but hardness potential more like 1084). it's not finely finished as far as knives go, but it's finished well enough for use. I can never get the handles on without getting a thumbprint of epoxy or CA when finishing somewhere, and just taping it to the hilt - not interested.

As long as a scraper is clean (1095) it can be used with abandon to scrape every last bit of anything off of the entire blade, and then at the end (still need to put more CA on the thumb notch and bring it up to a mild polish), a card scraper burr will cut neatly through the burr like a barber using a straight razor to sharpen the end of a sideburn, and it can be pulled back leaving a much neater look handle to blade than what's there so far.

I don't talk about scraping that much, but have experimented with it a lot because at some point, it's needed.



Earlier this year, I made my first archtop guitar and the only way I could think of to safely cut the arch with what I have around was to spokeshave off the very edges and then set a really strong burr on flat and curved scrapers and go from there. As in, almost all of the volume of wood was removed just scraping, and it wasn't terribly arduous.

I vaguely recall David Barnett talking about not just setting burrs, but controlling them and really getting the most out of them - most of his discussion was probably lost on folks, but his discussions of "there's a lot more out there than just rolling a burr and considering learning complete" (paraphrased) really kind of fertilize pushing to find out how far things can do.

I wouldn't be surprised if between the two of us, we could improve a whole bunch of things that are out there and get them manufactured and sold to the public, but a big part of doing that to make things work would be marketing the items and being only positive about everything surrounding them and anything else on the market. Not my strengths! someone would ask "will this help me make better things than a good screwdriver and a piece of saw plate?" and I'd have to answer "no. what you invest in actually making things and experimenting while you do will. anything "good enough" or better is pretty much all you need. We're selling the best for the gentlemen and the dandies".

 

[D_W]

tony, if I make an AEB-L card, I'll make two and send you one. I know you have a burnisher that would be able to handle it! I'll make sure that it's at least a little fileable with a good file.

I've got AEB-L in .04". It'll probably be a stiff bird at hardness and that thickness, but I'm sure I could eventually find thinner if it proved useful - the stuff is sold in strip and blanked into safety razor blades.

Again, practical gain? Probably nothing. I wanted it to be just the thing in plane irons, and it's good and long wearing, but carbon steel planes more finely for some reason, no matter how fine the edges start (and I've gone all the way down to 1/2 micron diamond on wood, which is bonkers). At some point, lack of some carbides to stay proud in an edge (at least of any size) and too much toughness becomes a detriment from what I can tell - in terms of how an iron cuts when the edge wears.

Magnacut suffers a little of the same thing. I'm sure it wears long, but the edge has the same feel as AEB-L (it looks the same under a microscope, too).

Even 1084 has a much bigger "bloom" of carbides, and 80crv2.

 

[D_W]

well, Tony - I've got two AEB-L scrapers in the steel sandwich in the toaster oven. It's not going to be a matter of whether they're hard - more a matter of whether or not the toaster oven has enough snort to temper them back until they don't kill a good file. But they'll be plenty tough even at high hardness.

if they turn out OK, I'll send you one in an envelope.

AEB-L has a whole bunch of characteristics that might be ideal for a scraper (retained austenite that could work harden in the burr, good toughness that will allow it to be as tough at high hardness as 1095 is at low, etc), very very fine grain and carbides,...

...but sometimes the result is still rubbish- we'll see. 52100 seems like it has all of the characteristics to be a great woodworking steel, but as it wears, it doesn't enter the cut very well in a plane blade, and you can feel that it takes more effort at same hardness in a chisel to get through wood.