Thread: More on garage heat treatment...

all of the results above are done by eye, judging heat temperature by color (you can use a magnet). I can see the color of steel at transition and have it memorized - at least in my small can forge (a bigger forge looks great, but temperature control is a lot harder because the whole thing is hot and you have no options of the steel starts to heat a little unevenly).

I am going to post a video of the process that I used, which is a subcritical quench series and then a final quench.

My high value tempering oven is a $19 toaster oven along with an $8 taylor oven thermometer and a stabilizing sandwich of steel or aluminum to avoid going above expected heat when tempering.

Interesting David.

That 26C3 steel has a lot of carbon at 1.25%. The comparison with blue and white steel in the first link is also useful.

Regards
Paul

I got toughness results back (the toughness test is more industrial or abuse knife related, but if it's OK, it sort of tells you that you nailed it if hardness is still good).

Historical charts from online experience (since hardening by eye is sort of a lost art, and developing thermal cycles by experiment, same.....) suggest that if steel hits the hardness target out of forge heat treatment, it often lacks toughness. Lacking toughness test performance is generally common.

At any rate, I matched the commercial cycle toughness test for O1 and bettered the commercial furnace schedule toughness for 26c3. Hardness for both is in line with optimal commercial cycle and quench and temper.

This combination is unexpected (I didn't expect it). The metallurgist who did the test didn't really mention other thoughts other than that he's usually gotten terrible samples from people who boast about forging or heat treating by eye (Forging itself can be useful as a form of reduction, but tools don't get full toughness if it's not followed by thermal cycling) - reduction is just smashing grain and busting up carbides, I guess, under heat.

This goes a little bit toward my thoughts from experience (that aren't believed on one of the US forums), that something like V11 has an idealistic wear profile, but it nicks a lot and I can't get life out of it that I can get out of finer-particle higher hardness steel (like an old ward iron), despite a ward iron or O1 iron at same hardness struggling to get halfway to v11 in a standardized test.

The notion that older steel was inconsistent or just lucked into is false. The last bed that I made for my daughter had knots in it and some mineral inclusions - the old hard ward that I have in my try plane was almost nick free despite being used as a try plane and bashing the knots off.

What is the case is that different older manufacturers seem to have chosen different hardness targets, and sometimes different within types of tools (which would've been done either by changing process, or just using a different carbon amount in the tools with the same process - e.g., increasing carbon in infill plane irons by .2% or so to get a couple of extra points of hardness).

What's also the case is that newer steels are harder to optimize, but more stable in quench and temper - the older steels can warp more and need a fast quench (Which increases the chance of warping). and newer steels can be optimized for better wear resistance, but it's hard to really get it if one is doing something more than planing MDF (like LV did) or planing a test board that's clean wood with no interruptions in the cut (as I did - V11 shined there).

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I have looked at the wear and failure profile of older irons from butcher to ward under the microscope and lack of abrasion resistance is their only real fault. That leads to easier sharpening at a given hardness and faster and cooler grinding, so the trade off is a fair one. It physically takes about 1 minute to sharpen a plane iron if you do everything as quickly as possible. With a more abrasion resistant steel, it takes more than one minute, creeping up on 2 - something like V11 or CPM M4 literally grinds slower and hones slower on a diamond hone (it's true that diamonds will cut anything, but they will not cut abrasion resistant steels as fast as they cut simpler ones). Long story short, the lack of failure in the simpler steels holds up its end of the bargain, but the more complex and easier nicking modern steels (A2 and V11) sometimes don't.

When a comparison other than nicking finds V11 to fail less, it's likely the only real issue is that the iron being compared is soft. For example - Lee Valley's O1 is tempered too soft. I could never understand why .Hock irons are tempered a little overhard, and I understand why he does that (it makes them feel sharper because they have some fine edge strength - but they will also chip a little too easily). Irons tempered as I have them here will be an excellent compromise and the O1 steel in this test will easily match V11 for an experienced user.

26c3 is a different animal - it's purely high carbon, no significant wear resistance in it at all (even far less than O1). It sharpens easily but it doesn't wear too long - it's excellent for an experienced user in a plane iron, but may vex someone who takes a while to sharpen. It does grind cool and quick, though.

So, why don't manufacturers do more work with O1 steels and other simpler steels at sweet spot hardness? I think it's not got a lot of bling and it warps more than something like V11 or A2. LN can't find anyone here who will harden surface grind O1 irons for them. I will make O1 irons for people in the states if they have an LN plane (not commercially, just off the cuff and not for profit). It doesn't take long.

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as far as japanese steels go - white 2 and 1 are great steels. Blue has some little bits of stuff and then a fair bit of tungsten - it'll nick easily sometimes. I've never been a fan, but some people like it.

I believe much of the reason that it was made is to improve knife toughness slightly, and to improve hardenability. I've had a lot of white 1 tools and the makers push the hardness too high and they're chippy. Buyers think they'll ruin them if they temper them back to the same hardness I got here with 26c3, and in truth, if the plane is a designer plane, they probably will ruin the monetary value if they tell someone they tempered the iron. But white 1 won't hold up well without chipping at higher hardness than 26c3 unless the wood is something like balsa. And the irons with a little more sweetness are just softer than people think they are.