AEB-L Hard Scraper

[D_W]

text coming after boosting pictures up from the phone. Just an experiment with cowboy toolmaking knowledge, like what will happen if you make a scraper that's more like 58 hardness (but in a steel tough enough to hold a burr without it breaking or cracking at that hardness) vs. one that's 48.

made out of AEB-L stainless, a blanking steel made for razor blades that's actually finer in grain than most plain carbon steels (the common plain carbon steels are all far finer than A2/V11/PM D2, etc).

 

[D_W]

So, the thoughts behind this are:
* will the strength of a harder burr lead to a better surface or better uniformity
* will the wear resistance of AEB-L improve the life of the burr (I have my doubts about this, actually)
* will the stiffness of a harder plate allow keeping thumbs further away from the edge so that there is no thumb burning
* can I key all of this to be aimed at a carbide burnisher since I have one already and at one point polished it with a diamond-impregnated buff

Initial thoughts:
* it's not a non-trivial thing to actually heat treat shim thickness steel into something that you can hone the face of - as in that stays flat. I have a pair of plates that are a transitional step heat treating knives, so they came in handy here.
* It would be nice if they were actually slightly softer. they will file with a fresh file, but a typical used file floating around the shop is just barely better than an even match
* I cowboy flattened and sharpened the scraper here. if it gets used going forward, the face will gradually become honed. it hones finely compared to a typical scraper due to the hardness
* the feel of the burr and the scraping is like grease. you can feel chromium in stainless steel tools if they have a good enough edge that you don't notice a bad edge
* at this hardness, the steel has excellent toughness and will tolerate drawing a burr. However, it's not trivial even with a thin carbide rod to actually draw out and roll a burr
* it is true that the hardness and stiffness allows keeping thumbs away, so there are no hot thumbs. In fact, i'd say it doesn't bend easily enough to warrant thumbs down near the cut to control the steel - it'll just create sore hands. A more general flex of the whole thing is fine



I want to get an idea of whether or not the burr can be refreshed more times without refiling and honing. it seems possible - as in, it should get ragged less quickly. I don't know that for sure.

For now, this is a dead end venture as my steel stock is .04" and I can only get it in widths up to 1.8". both thinner and wider stock would be better.

There's virtue on curved work in being able to set a large burr and remove material (guitar tops, necks, etc) but the hardness makes that impractical with this

there are some specialty bits of steel sold to people who have trouble rolling burrs, but want to use their scrapers on nasty woods. I think this would tolerate that (I can check that, too). I don't care for scraping with a square edge - it doesn't last long and the quality of the surface is more like "scraped" than cut off.

 

[D_W]

you can click twice on the picture above and get a good look at the shavings close up. On maple, this is pretty wonderful - i've now re-rolled the burr four times and it still makes shavings like this, though the surface is getting a little more dull (not nearly as dull as even 600 grit sanding, but the initial edge makes a reflective surface that you can see a clear defined reflection in)

 

[D_W]

On the fourth re-roll of the edge, this is what the burr looks like:



Interpreting the image, the very thin white line across from the dark area is the tip of the burr.

the darkness in between is due to the curvature of the burr - it's a metallurgical scope - whatever goes straight down in light and comes straight back up to the lens is seen. It's not that the burr is dark, but rather than the light hits it and goes diagonally off to somewhere else.

however, notice how good the quality is of the burr fineness despite being re-rolled several times. Just dandy. what it implies, and what it turns out to be in practice is that you can take a thick shaving with the same big burr, or a very thin one, and it will pick it up, not just scratch over a surface.

after preparing the second one, it does remain the case that the edge is hard on a file, but I have a lot of half used files that I can torture.

I file a bevel freehand something like 20 degrees off of square instead of square, and then stone about 10 degrees off. that gives two burrs instead of four, but they are much higher quality than i've seen anyone get with a 4 sided burr, and the process is effortless (easier to complete). it turns out to be more efficient in use.

the only catch is that in use with a commercial scraper, it's not always easy to see the bevel on a thin scraper, and you can end up sharpening the wrong way. A piece of tape on the back would probably solve it, but the oilstones remove everything. Definitely, permanent marker is gone as soon as it meets oil a week later.

But, since I made the scrapers, I can leave the scale from heat treatment on one side or both and it's not a pain to see which is which.

 

[D_W]

to compare the fineness of the burr, see this typical picture that I share as a calibration view - the edge of a plane iron that has been sharpened with an 8,000 grit waterstone that was slurried. Note that the evenness of this scraper edge is actually better.



Because the scraper is pretty hard, the edge can be had in this shape off of a fine india - no fine honing is needed - I guess the carbide will consolidate what's left, but honing the long edge or long face combined with the hardness also prevents the abrasive from leaving deep scratches.

 

[D_W]

So, how long does it take to make one of these scrapers from bar stock (keeping in mind, it spends a while in the toaster oven, but that's unattended. it's a stretch for my toaster oven to make a thermocouple read 450F continuously in the blocks that I temper things in, so this is as soft as I can get these scrapers without coming up with a way to temper at spring. these do flex but have memory to go back to original flatness (I guess that's spring, even if it's hard tempered spring).

At any rate, with heat treatment and prep, it takes about 15 minutes to make the pair, maybe 20 due to the prep time (for both).

the cost in gas for heat treatment and steel stock is probably $4 in total for each one.

this has been a worthwhile experience as the burr's stiffness prevents it from rolling over very far - the scrapers can be used very upright even as the burr gets a little bigger with successive drawing it back out and rolling it over again. You can feel the fineness of the cut, and you can see it on the surface of what's being cut.

 

[D_W]

If one is OK, then you always make two to check to make sure both are the same, right? that may not be normal, but I do like to make at least a pair of something to see if they can both be the same. You can see #2 below with #1 above. Same thing - temper is about the same, feel is identical. This is a good thing. You can see from the edge prep that even if you plate harden this stuff, it's still not dead dead flat, but it's flat enough.




Cowboy sharpened again, only fine india stone, then burnish with carbide. Again, wonderful fineness without having to do anything more to prep the edge, and this one will get a little more uniform with subsequent cycles. I'm leaving the heat treatment scale on it for ease in identifying which face gets lapped. the grip is also slightly better with it.


the feel again is smoothness and the burr is too hard to be rolled around too far easily. A dandy side effect.

I just wanted to confirm that shellac really doesn't soak in much, and it doesn't, but getting a good scrape is kind of like planing - on a sheer finish, things show up that don't appear with sanding, and the sheer finish can be far thinner.



so this plain board, when you look back against the grain, has interesting bits that you can click in on - only difference is viewing from a lower angle and then straight over.


I realize commercially, all of these little things are "blotch", but I like to leave them and be able to see

 

[D_W]

final thought on this - the hard scraper remains just dandy except...

...I lost track of my carbide stub burnisher (round rod about 3/16ths) and used the two cherries triangle burnisher and I don't know for sure what the issue is, but the edge was ragged afterwards leaving a surface that would have to be sanded, and removing material slower.

so, before I call this scraper an improvement over the 1095 types, I guess I need to compare those using the carbide burr. I think something odd goes on with the hardness too close - like with vigorous drawing out of the edge, and then turning the burr, there might be adhesion. No new oil is needed with the carbide stub.

Blanks to make a burnisher like that are about $5 here online, but you have to polish them. To have unpolished carbide would be kind of pointless because the grinding marks, even if fine, are going to leave an impression on the edge of the burr.

With the burr as shown in the top picture above, the feel is almost like the edge is greased through the wood. Super smooth, the wood comes off fast, not in strings, and the result is excellent. if you just had to sand it, there's nothing that a linear hand pass of 400 grit wouldn't remove very quickly and provide a uniform surface, but the finish as it is is more than suitable. My motivation here is to improve the work of the scraper enough that finish uptake will be similar to flat planed surfaces.

Sounds dumb if you like to sand everything, but the first padded coat sits *on* the wood rather than being absorbed in very much. Two or three padded coats is like 5 on a sanded surface in terms of finish uniformity and thickness and there is no raising of the grain.

 

[D_W]

so, how do you quickly polish one of these? 5 and 1 micron diamond laid on wood with a little bit of oil and put the stub in a drill and draw it back. then, just drill a hole in anything, scrap dowel or whatever and glue the stub in.

that adds about $15 here tracking down the smallest vial of diamonds (about $6.50 each plus tax) , but those will be useful at some point in the future if you have them on hand.