Carbon steel (plus AEB-L) test

1095 - 836 feet

David Weaver

1095 at, guessing, 62 hardness (shot for higher, but chipping was a real problem)

-836 feet planed.

The test included 200 feet of against the grain planing and the rest with the grain. Cap iron set just off of where I normally would for easy wood. against the grain planing is a bigger challenge for edge toughness and when I make an iron from now on, I may test it against the grain on maple instead of with the grain.

This iron experienced uniform minor chipping against the grain. I think that hindered the final distance. The edge wore cleanly enough that the chipping was abraded off by the end of the test. None of the chips from the initial edge would've been big enough to easily catch a fingernail, they just made tiny lines on work that could be seen.

Picture 1 at 433 feet:

Edge at the finish - the picture is wonderful. The iron wasn't quite as nice to use as the picture, but it's OK. No reason to switch from O1.

1084 - 997 feet

David Weaver

Unexpected - lower alloy, but one where there isn't much free carbide in solution when it's austenized (heated past critical). No normalization needed (soaking a steel at high temperature to dissolve carbides and get everything in solution).

997 and more pleasant to use than 1095. I would guess the iron is a point or so harder than the 1095 iron, but it's also tougher. Technically, 1095 wears longer, and the CATRA knife tests show it doing so vs. a steel that's a little lower carbon than 1084, but those tests cut a sand-impregnated card and don't test a combination of strength (being hard enough to avoid deflecting) and toughness (not chipping or breaking out) like planing.

Sharpens very easily, even at high hardness. Really easily. two tiny nicks in the iron the whole time - they may have been my fault, but they were big enough to not wear off like the disturbances on the 1095. No other edge issues. This iron did not have decarb steel (the outside rolled layer ground off), but all others did. It also loves the buffer (the buffer will actually cause damage on an iron that's lacking toughness at high hardness or one that's absurdly soft if you don't buff a bunch off).

Picture 1 at 433 feet:



Picture 2 at the conclusion.

I see no reason at this point to use 1095 in a plane iron if 1084 is available. Its combination of toughness and strength are better so it can be used at a higher hardness, negating any advantage 1095 would have.

52100 - 1235 feet

David Weaver

52100 is slightly higher carbon than 1095 with small amounts of alloying elements. For our purposes, it's a better steel. It's not quite as easy to find in bars in the right thickness (knife people love it).

It has a very sweet feel. CATRA knife testing found it to wear longer than O1 - I found it to be almost identical. It gets to the same place with a slightly different alloy. Very sweet steel, but water hardening and it does warp. I like it. I may use it instead of O1. It sharpens a little bit easier on the india stone and washita than O1 at similar hardness. I don't know why .Someone using synthetic waterstones probably wouldn't notice anything.

1235 feet - noticeably better in feel in the same planing task vs. 1095, and smoother and crisper in the cut than 1084. Lovely uniform edge wear and good toughness at relatively high hardness. Probably 63 hardness, my guess. Tempered at 350 degrees F.

At 433 feet:

At test conclusion. Lovely.

O1 -1231 feet

David Weaver

1231 feet from the O1 iron that I used in the original iron test. This iron is also hard, probably about 62/63 hardness, and is as good of an O1 iron as I can make.

I suppose I hoped to find out that 52100 would outwear it, but they're about the same. Very similar in feel, etc, and O1 is less demanding in heat and quench (it gets full hardness in preheated soy oil, no problem. 52100 benefits from a special quench oil, though it's not needed, it does get an extra point or so of hardness.

we've seen this iron before, so here are the edge pictures from today:

at 433 feet

end of test

I have no idea what the original thing was that caused O1 to beat out 52100, but maybe it warps less.

AEB-L - 2097 feet

David Weaver

AEB-L is a steel developed for early stainless razor blades. It has a low carbon amount (0.67% or so) and something like 13% chromium. Whatever happens, the carbides end up being tiny. This is a fairly big deal for us in plane irons if surface quality matters. The carbides in this steel (non-PM) are much smaller than XHP, CPM 154, etc. The pictures of it look better than japanese steels other than white (even blue and blue super have far more foreign bodies in the matrix - the guy running this site took pictures of those. Interestingly, I never liked blue super - I thought it would develop chips at the edge and spoil a surface, and micrographs of it show that it doesn't have that many carbides in it that are visibly large, but the couple spotted here and there are really large. ).

https://knifesteelnerds.com/2019/03/04/all-about-aeb-l/

So, the small carbides allow AEB-L to go to very high hardness (like 65) and have toughness that's reasonable (higher hardness means longer wearing if no damage, varies by steel type, but low end range to high end of hardness range with no damage can be 20% or so gain, and better sharpness/sweeter cut using the same abrasive).

This is a stainless and it needs a commercial cycle and cryo treatment to really hit top hardness marks (cryo treatment for 36 hours can add a point on the c scale, maybe a little more). It also needs a 10 minute soak at 1950F or so, which is something I can't do. I don't know if I can get 1950F with two mapp torches and a paint can forge, but I can probably get close.

The first attempt at this, I wasn't thinking - I heated it just past where I would heat O1 or 52100 and figured I didn't need to melt the chromium carbides (I don't think they're small, though, until dissolved into the steel). I had edge breakout everywhere and the steel wasn't very hard. I took the iron out of the test after 433 feet because results were unacceptable - I've never seen lines on wood like it made, and...again, soft. It was a pain. Even the buffer damaged the edge a little bit, but just a little. Accumulated damage was fast.

Scratch pattern is deep in the above picture due to being relatively soft. I'd guess 56/57 - no go. It's not saw or spring temper or anything, but things change fast below 60.

So after I finished the other test, I figured (recalling that XHP only really needs to be heated hot and then it's good to go - there's no big carbides in it at the start to soak in) I'd take the dud iron and put it to high heat for 2 or 3 minutes and hopefully that would be enough to improve things, but not enough to ruin it in the open atmosphere.

It outlasted everything else easily. It's still a little soft. I don't think I had the cap close enough for this second test - it did the same shift - 200 feet against the grain, the rest with (but all in one area of the board right after the other tests ended), but it's clear that it has a ton of potential.

It sharpens *just* like a soft carbon steel, offering no resistance to the india stone and rolling up a big burr on the washita easily.

I think the test is out of line, though. CATRA testing suggests terminal performance about 50% better than 52100. It won't match XHP for terminal performance, but I think it has the potential to wear better than A2, sharpen easily on oilstones and it's inexpensive (about $8 per blade, but you do have to belt grind or do something to get a few thousandths off of the bars as they're not decarbed and the first few thousandths are probably trash).

The picture of edge wear at the terminus (there should be a scoop on the back. I expect if I'd have had the cap placed a little closer, it would lose a little bit of edge life and be closer to the target. I may try tomorrow, but it's not really worth the trouble).

The challenge for me now is to get hardness up some from where it is. It's *really* easy to sharpen as-is, almost too easy (a little soft), but time will tell.

Also - it isn't a modern super stable steel in the quench. I don't think we're likely to see anyone trying to make commercial plane irons out of it - it sharpens like carbon steel, and it warps like carbon steel when it's quenched.

If I handed someone a filthy iron just tempered, and asked them to freehand sharpen it on oilstones, though, they'd never guess it's a stainless steel.

Super high toughness, much higher than a lot of high carbon steels at hardnesses around 60, though. I just have some experimenting to do to get high hardness out of the quench and then come back to something like that after temper. I'd guess right now it's struggling to reach 60.

I don't believe there's any other stainless with such toughness and tiny carbides.

The visual trap...

David Weaver

..for this second quench on this mule, I just sharpened quickly on india, then washita and buffed off the wire edge on the corner of the buffer (no heavy contact into the wheel).

This pictures are all visible light - there was some cap iron action in this test, but maybe not as much as others.

The fact that it looks like there's no scoop out of the back of this iron may be just a visual anomaly, though - I'm less concerned about the visual and more concerned about the result being so high (why so much higher than 52100 and O1?).

Pictures alone don't tell the whole story, though - the 1095 pictures just look grand, but the tiny chipping and dull surface at the outset weren't imagined.

So, I do expect that this (AEB-L) will beat A2, and 52100/O1 at this game, but probably not quite as much as this ratio. Lost of promise with it, and though it does warp, it's so easy to sharpen (I flattened it after the second quench - and yes, if you harden something, then flatten it and then harden it again, it warps again - just with the india stone - the 52100 and O1 are hard enough that they were a bit of a chore to flatten comparatively).

Re: AEB-L - 2097 feet

Wiley Horne

David,

Excellent write-up and equally interesting deep background article!

Thanks, Wiley

Re: Carbon steel (plus AEB-L) test

Philip F Duffy

-- -just a footnote on 52100. I HAVE 2 knives of 52100, one I made myself and one by Chuck Oakes of Florida, a Master Knife maker. Both have cleaned multiple deer in the field and never needed sharpening. Both have been used to butcher the deer and performed perfectly. Both have been run across a leather strop a few strokes before the season and that's it. Amazing steel.

knives

David Weaver

It's a very good steel for knives, as would be AEB-L if I had a vacuum furnace and nitrogen dewar. There are adjustments to both that can be made (thin bevels, high hardness) that higher carbide steels don't tolerate that well.

The "super steels" are good for standardized tests when those items are normalized out by requiring same angle and same hardness.

With plane irons, we're kind of limited in taking advantage of the things that make it great for knives, but it still makes a really nice plane iron and this is the first one I heat treated (it's dead simple to heat and temper in open atmosphere). Nice stuff. I have to guess that it's not used in woodworking tools more because it warps (but the amount it warps doesn't matter for someone working by hand). It'd be good stuff for chisels forged in a two step die like they still do in europe.

Re: AEB-L - 2097 feet

Bruce, a MN Galoot

We were at a pottery shop yesterday. I talked with the owner who said that their electric kilns reach that temp, and the gas fired one hits 2200°. Just an idea.

yes....

David Weaver

..knife ovens, which are probably not much different than ceramic kilns, will get up to that range. I have a propane forge that will get that hot, but temp control isn't precise like an electric furnace.

I think what I did was decarb the outside some, as I resharpened the iron twice now, and it's quite hard, so It looks like I just had a misconception about where it was.

This would make some sense, as I kept it at a very bright orange that was just next to dull yellow or right around that transition for several minutes - it should have decarbed, but there's not as much carbon in it as O1, so I didn't see any pooling on the surface.

Now, what I have left makes me feel like I'd like it a little *less* hard than it is. Call me see-saw. I'm just learning with this!

A good knife furnace with some length and good temp control is about $1500 new. As important as temperature control is (the range for these stainless steels to attain high hardness is about 50 degrees, or maybe 100 - too far above that range and there's a lot of retained austenite and hardness suffers without cryo treatment (I did already look up the price of a dewar, and that's out!).

That said, I got a pleasant surprise finding the iron to be much harder after sharpening off the skin of decarb that I created by heating it to high temp. I never had to deal with this before because XHP just needs to get to temp quickly and then quench. Maybe it's not optimized like that, but it works pretty well.

Thanks for the suggestion, though - a good ceramic kiln may be something down the road that I could get by the wife as the daughter would like to make some pottery and we have no way to glaze it. I'd also like to try making pencil leads, and they need the same - a high temperature soak.

AEB-L test 2 - 1950 feet+

David Weaver

This is actually test 3 - I ran the second test into contamination inside maple and had to flip the board over and restart. When encountering the damage, the edge deflected more than chipping and I could feel a burr on the iron even though the damage was uniform enough that I couldn't see it with a naked eye like you can see a notch in an edge.

So, I was wrong about the hardness - It appears by holding the steel at high heat, i made a decarbed skin on the outside that felt soft. Honing 2 and 3 and it feels like a hard carbon steel now (raise a burr on the india stone, but not quite so fast as before, and then take the burr off on the washita while refining the edge and there's not a real dingleberry of a wire edge like there was on the soft outside).

In order to try to immunize the iron from the damage in the maple (which luckily didn't occur on the other edge of the board until I got to a long brown spot in the middle), I gave the tip a little bit of a buff - call it 1/2 uni. This is a trade off - it reduces clearance in return for removing the edge apex. The opposite side of the board was slightly less pleasant planing (less predominant grain direction), and I expected low performance (you can feel the slightly reduced clearance of the initial edge if you do a lot of planing), but the iron was still cutting 2 1/2 thousandths shavings at 1950 feet.

Based on the abrasion data, this also suggests the hardness is pretty high (I would guess now that the core of this iron that I seem to have gotten to is low 60s or it would hold its wire edge better given the toughness). So.....I could make these irons.

I also do believe that for good edge behavior, it may like a degree or two of bevel over 52100 (like A2), but its edge uniformity is miles better than A2, and edge life is longer, and it doesn't mind the washita.

I cannot get it to take on the scooped look that the other irons did, but it may be that it just isn't seen easily - this is the edge after 1950 feet. I don't know how much longer it would go. Could be 100 or 300 feet, who knows, but pushing an almost dull iron for 500+ feet already, I had enough.

Notice the nice edge uniformity in terms of wearing - unusual for a stainless.

Using paraffin on your plane sole will prevent..

David Weaver

....rust on your iron.

I figured something out I hadn't thought of before. For eons, I've thought remaining oil on the back of the iron showed up on the bevel when I wiped the wood cake/goop off of the iron tip.

I just realized today that the film that's on the iron isn't oil, it's paraffin. when you plane, the paraffin can melt and end up going up through the plane. This film goes all over the iron near the tip, so it may not protect from rust away from the tip, but it leaves a noticeable film of wax on the iron.

That also explains why I thought it was so much work to wipe oil off (it still is - if it's oil right after sharpening, it takes a long time to get all of the tiny scope drops of oil off.)

You can see a couple of tiny lateral scratches on the iron that I have that's already planed 1950 feet. I would see this and say "how did you get little fresh scratches like that in such a worn edge?" The answer is that I had to get fairly rough with this iron (on pants and carpet) to get the wax/stuff off of the iron tip. I probably have metal dust on my pants (I know for sure there's some in the carpet near my scope as I wet vacuumed the carpet in the basement next to the shop last week and let's just say that there was more black metal dust in the bottom of the hoover wet carpet vac than I anticipated. The dirt stayed on the top and it went to the bottom of the wastewater apparatus.

And lest I think it wasn't metal, what little bits remained that I couldn't see but didn't get rinsed out.....they rusted in every little scratch in the laundry sink.

So there's plenty of opportunities for scratching (and even normal people dirt would do it).

Re: Carbon steel (plus AEB-L) test - question...

John Aniano in central NJ

David,

What did you mean when you said ..."make one iron of each type, and temper back only until lines on a piece of test beech don't appear"...?

Are you testing the temper temperature by burning/scorching beech? If lines do appear, you've gone too high in temperature, right?

If so, this means you're not using tempering colors, right?

John

tempering...

David Weaver

.by that, I mean that a lot of tests normalize various steels to a given hardness or geometry, but what I'd rather do is leave the irons as hard as they can be with acceptable toughness. 1095 is the exception here - I tempered it back a step further than the 1084 iron but at some point, the loss of hardness will make it wear shorter than 1084, anyway, so there's no reason to chase it down to a much softer point (1084 is just a better choice with the two bars that I have).

So, for everything else, what I did was quench and then temper about 50 degrees below the target point. If the steel would tolerate that and not chip, then I'd leave it, but nothing really met that standard (the files do for chisels, but that's it for me so far - they can be bonkers hard and still perform well, but they're not easy to sharpen at the point where they stop chipping).

Anyway, I would plane about 50 or 100 feet on a test board and look for any defects (lines) in the surface. If there are any, then I temper 25 degrees warmer, which should be about a point on the C scale. At some point, irons stop showing small defects and then that's my ideal temper (where an iron will wear the longest - the point where it's hardest and doesn't collect defects).

For O1, this is about 400 degrees. For 52100, it's about 350. Both seem about the same hardness. I can't remember what it was for 1084, it was probably also around 400 as there was a little bit of tempering color on the steel.

AEB-L, i tempered at 300 and it's OK - I think it may be a bit too hard and I'm going to temper it another 25 degrees.

This isn't a perfect test as planing against the grain with a fresh edge in some woods will damage an initial edge, but it wouldn't damage the exact same edge that's already planed 400 feet (the apex is worn off of the edge by that point and the edge is harder to damage even though it's a bit duller).

I did the first part of this testing planing against the grain, because I didn't think the board had a dominant direction and there is a little bit of reversing. It's hard maple, unpredictable, and every iron had a tiny bit of damage, but 1095 and AEB-L had more universal damage. In my third test today, I ran into some contaminants with AEB-L, and it's also noticeably harder after sharpening a few times, and those damaged the edge - I don't know if it needs to be tougher, but if the test is early, I will slide the iron offset just a little bit - if the iron takes damage from the same spot of wood after moving the cut point for just a few strokes, I know the wood has a murder spot in it (vs a defect just in one spot of the iron).

The can forge allows for supremely even heating of just the business end of the iron, so I haven't had any iron yet that I can recall where the treatment was inconsistent. The whole edge is pass or fail.

Not sure if that description helps, but I guess a shorter way to say it would be to say that I intentionally temper hard and gradually step it back. As soon as the next level of tempering doesn't result in edge damage, then I stop and leave a given iron as hard as possible.

A good steel and a good iron will have a gap between toughness and strength where anything in between will work well. Low hardness and maximum toughness results in an edge that folds over (if the steel is good steel). High hardness with little chipping is a lack of toughness, but generally good strength in a steel. A forgiving steel like O1 will give a solid 4 or 5 c-scale points of reasonable tempering range whereas a steel that struggles to achieve high hardness will be on the low end as soon as it's tempered back. That's where I thought I was with AEB-L, but I was wrong.

There are tricks to increase hardness, even with open atmosphere (you probably know these already, but others might have some interest):

* increase austenizing point (at some point, a peak is reached and things go the other way, but austenizing to a point higher than critical by 100 degrees or 200 always gives me an iron that starts harder and has good toughness at higher final hardness. too much time at higher temperature increases grain size, but short periods don't cause ruination all at once.

* if a steel tempers in air (like XHP/V11), tempering in oil can yield another point of hardness in many cases, as long as the steel tolerates it. AEB-L is generally plate or air quenched, but it tolerates oil (which may explain why it's now harder than I expected it could be after temper), just like XHP. Knife makers probably like plate quenching because they can squeeze a blank between two plates and minimize warping - It's not a big deal in plane irons that are OK to look hand made.

* freezer for 24 hours (will add about half a point)

* true cryo treatment in nitrogen for 12-36 hours (can add a point or point and a half).

Since I'm not doing cryo, and I don't feel like waiting for the freezer, I'm choosing to oil quench to try to make up a point of hardness for it. On 52100 and 1095, a fast quench oil gets you that point over a heated vegetable oil since the fast transition steels are very sensitive to the initial temperature change. O1, it seems to make less of a difference (which would make sense since O1 is designed to achieve full hardness in an oil quench).

A2 picture for comparison

David Weaver

we're looking at a lot of nice worn edges in these pictures other than the failing AEB-L edge after the first poor-method heat treat.

I thought that showing the irons from the last test at the same magnification would be interesting. This is A2:

This is the chinese HSS:

And the japanese blue steel:

And V11 - which had pretty nice edge smoothness in clean wood, better than any of the three previous here:

9000 feet of shavings

David Weaver

I've heard a time or two vs the last test that I couldn't have planed that many feet - this short test is far fewer feet and in far less time.

This is what 9000 feet of maple shavings look like (the pile is a bit taller than both picture show - second picture to show the depth of the pile).

I'd normally vacuum a pile like these with a leaf vacuum, but learned last time that maple is like fishing line (burned up my favorite older electric leaf vacuum). Strangely, beech goes through through the leaf impeller and shreds without issue, as does almost everything else except for maple and some pine.

Re: 9000 feet of Gerbil housing

Bruce McCrory

Years ago we were always looking for cheap guinea pig bedding for the family pets.

Won't there be differential temperatures in steels of variable thickness when hardening, and tempering that will impact Rockwell rating?

Note: I can barely boil eggs for proper peeling. Heat treating is totally alien; but I try.

It depends (temps)

David Weaver

I heat steel fast, but a metallurgist said they consider "fast" to be induction heating, and i'm heating it slowly compared to that. Salt baths or molten lead are also not considered fast, they're considered medium.

the bottom line with that is that I can move the cutting end of the blade around in the forge until it's uniform color front to back.

If I had a forge where I couldn't easily do that, it's true that (even if you just put steel under a torch) that flame patterns can create cooler spots, sometimes right even in the middle of the flame. I am generally moving the steel to get uniform color more to avoid overheating the tip of the iron (something much easier to avoid doing one at a time).

There's a follow-on to this, though, and that is the transition rate required for full hardening. If you harden a thicker file (like over 1/4th inch thick), it's possible in an oil that's borderline fast enough, the center will be less hard than the outside, or the outside on a thicker item may not transition fast enough. I got a fast quench oil (parks 50) to work around this, but did read on 52100 (which is more forgiving than 1095), water quench may be needed to get full hardness through and through on cross sections thicker than 1/2".

I'm guessing a little here, but I think I'm more accurate than most commercially heat treated irons with the exception of a few being done in a vacuum furnace to a very strict temperature cycle. I think most of the changes to inexpensive steel have been done to make it harden more predictably with poor quality heat treat and quench (like a quick induction harden and then quench literally by a spray of water, and then induction tempering and another spray).

I've got two forges and am not sure that on the larger propane forge, that I could get the temp control that's possible with a smaller forge and a smaller more intense heat source. It's hard to sit or stand that close to a propane forge running full on - if the front is open and you can see a lot of areas radiating orange inside the forge, the radiant heat coming out of the front is intense.

If I were going to make tools to sell, I'd probably track down a hardness tester to see how accurate I am, both in consistency within irons as well as between. I don't have anyone to beg or borrow from at this point, though.

misunderstood the question at first..

David Weaver

..read.

The short answer is that if the steel is thick enough in some areas to meet the transition requirements, it could be softer in those areas.

Experimentation and some reliable abrasive is needed.

I don't know what files are made out of, but I sense that the really heavy chisels that I've made with them (thick in cross section) in soy oil are ever so slightly softer after quench (but still way too hard to use ,and have plenty of room to temper back). A thicker cross section of 1095, like a half inch in oil may not harden through and through, but heavier cross sections also don't crack as much in water, so water can be used if the fastest quench oil doesn't satisfy.

The other short answer here is that anything we make in woodworking tool shapes isn't going to differ enough to matter, and if it would on a heavy cross section chisel, it would do it in a favorable way (the business end would be slightly harder, and as the cross section increases toward the tang, it would be slightly softer and tougher).

I sent an email to Lie-Nielsen...

David Weaver

..suggesting that they look at trying AEB-L since they no longer provide O1.

It sounds odd to suggest a stainless to replace an oil hardening steel, but the edge quality is about the same as O1, or only very slightly shy of it.

I provided them with the test results gotten here, some edge pictures and discussion about workability of the steel and heat treatment (no more challenging than working with A2 if it's plate hardened, same cryo and tempering process - not hard on tooling).

Got a fairly favorable response...

David Weaver

..one that acknowledged items I said in the email meaning they actually read it, and they'd consider it worth looking at.

Call me a cynic, but I figured that the chance of doing that is pretty low (it doesn't really solve any problems for them - I don't think many customers avoid LN planes due to A2), and am pleased that they did read what I wrote and responded as quickly.

If they did test AEB-L and implement it, I wouldn't be surprised.

I have some experimenting to do now plate hardening it. Years ago, a friend of mine had a huge solid aluminum fence with a .2mm step milled into it after a hollow slot. It's intended to joint small wood with a router .2mm at a time, with the cutout in the middle to allow space for a spiral bit. It works. I also never use it and never have, but it's inch thick 6061.

I can saw it into pieces and plate quench as AEB-L to see how much that helps flatness. I know this sounds stupid to most people, but it's just a hobby. If it plate quenches or air quenches with the same stability as A2, I see no real reason to use A2 for plane irons - ever.

Re: Nope, you explained it well

Bruce McCrory

Thanks, David. I got sidetracked and forgot to get back to this detour in the discussion. I was trying to find a relationship with katana heating where they coat portions of the blade with what must be clay slip prior to the final(?) heat.

Yes on the clay..

David Weaver

...there's two ways to do that - one with the clay, and two - with shorter knives, using a water hardening steel and leaving part of the tool out of the water.

A million ways to do things by hand (interrupted quenching, etc.). Those are all off of my radar - I'm not worried about warping or cracking, just getting full hardness.

I'm guessing katanas are mud covered because the size and geometry of the sword makes it impractical to differentially harden any other way (they have to be plunged, and it only works because the transition of water hardening steel has to be so fast that even a little bit of clay will prevent full hardening).

Compare that to what we're guessing V11 is made of - the transition requirement for hardening is 50 degrees F per *minute*. Very well designed to achieve full hardness with almost any method. Not so easy to deal with if you accidentally heat it in the shop, though (accidentally make a small spot hot, even a contact point in front of bandsaw teeth, and it'll be full hardness in seconds - like trying to saw ice with a butter knife.