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I'd guess colder would be better because of the explanation here :

https://en.wikipedia.org/wiki/Cryogenic_hardening

I have no experience with this in real life, though.

cheers.

"Cryogenic" was the word I was missing from my search, thanks. I'm not too sure a home freezer would come anywhere near the temperatures needed to make meaningful difference. It looks like they are talking about temps in the liquid nitrogen range but I'm not sticking any of my tools in the liquid nitrogen tank any time soon. It also looks like there is a lot more to know about steel and the cryo process than I want to learn. I may toss my Aldi chisels in the -80 C for a few days just for the heck of it though. I picked up a set just to see what they were all about and use them every now and then when an abusive job comes up so why not?

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Bryan Bear PMoMC

Take care of your feet, and your feet will take care of you.

What? Aldi chisels aren't the greatest thing since sliced bread? I'll bet Aldi was happy to move so many cheap chisels. For guitar building I know I could get by with one good chisel, but it's more fun to have dozens to play with. The more the merrier!

It seems obvious that they wouldn't be stellar and I'm sure there is a large degree of variation from lot to lot, but the ones I got aren't too bad. The worst thing about them is the handles. They are easily better than the chisels I made my first several instruments with (but that's really not saying much).

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Bryan Bear PMoMC

Take care of your feet, and your feet will take care of you.

So... My caveat here is that I am not a metallurgist and I don't have any specific composition info on the alloy...

That said - the Marples (and a number of current Chinese chisels) are some sort of water hardening steel. I have re-hardened a few and know that much... If you look at the TTT diagrams for water hardening steels - you will see that the hardening process doesn't fully complete until below 0F. Most industrial HT programs go through a series of gyrations to avoid warping and cracking - which includes not cooling the steel down quickly once it hits about 400F... And they generally don't intentionally freeze them due to concerns over cracking.....

And so my current theory is that freezing them perhaps finishes the "quenching" process and you could gain maybe a few % more martensite - which makes them a bit harder.... YMMV...

Now... Cryo is a different thing... If you read the literature - it says something vague like "On avgerage, no increase was found" blah blah blah.... What the data really shows is *not* that nothing changes - but rather that some test parts get quite a bit harder and some get quite a bit softer but once you get a sufficiently large number of different samples - it mostly averages out to zero.. For example - a fellow on another board -80 tested 2 Blue Spruce chisels... 1 got 3 points harder (Rc58 to 61) and the other got 3 points softer! (Rc 61 to 58)... So on *average* no change - but big changes happened to each chisel in real life...

John, I did some very quick reading about cryo treating and am not surprised to hear that you the results on the two Blue Spruce chisels were mixed. My quick take-away was that there are way too many variables and unknowns for me to have any business doing this. It would be one thing if the expectation was either better or no change but if there the third option is worse, I won't really bother.

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Bryan Bear PMoMC

Take care of your feet, and your feet will take care of you.

Bryan,

I think it's important to say that for a decent collection of different western style "wood chisels" in general - hardness is not strongly correlated with cutting performance. It's interesting that if you look at some or the "shootouts" that focused mainly on hardness - often their advice is to buy "quality" chisels that feel comfortable in your hands....

Within a bunch of chisels from the same maker/same lot - hardness does correlate very strongly with cutting performance... But that makes sense because nominally everything else in their process is the same...

So what that tells me is that the specific material (alloy and form of the material) and the manufacturing process itself has a lot to with the results you see between chisels that may have very similar alloys....

For instance.... At one point - Harbor Freight, Aldi, Marples, and Woodcraft socket chisels all advertized 100CrV alloy... But yet (for me at least) Marples and Woodcraft chisels cut like "real chisels" where the HF and Aldi chisels just simply don't hold up... So marketing copy said the alloy was nominally the same... Hardness was very similar.. Yet the "good ones" cut 2 or 3x better than the "cheap ones"...

Another example is Pfeil chisels vs Woodcraft green handle chisels... Both were nominally made of the same or very similar alloy, similar hardness (my woodcraft green handle chisels were a touch harder than my Pfeil) - yet the Pfeil cuts 2 or 3x better than the Woodcraft...

So there is some "secret sauce" that appears to deal with crystal structure and grain flow in the steel... And makers achieving high cutting performance have sorted this out and are doing whatever "it" is where the others aren't... One piece of this sauce is that Steel is anisotropic like wood... The properties of the steel "with" grain flow direction can often be 2x that "across" grain flow.... Compressive strength is one that is very strongly effected... (Does this sound like talking soundboard wood? )

For all you guys in to modern chisels - first come, first served:

http://www.supertool.com/forsale/2018maylist.html

Look at ST27

Ed

I like the E.A. Berg chisels from Eskilstuna Sweden. Good steel, well made, hard but not *too* hard, they can be found on the bay for $10-30.

Ed, that is quite a list and has me drooling. Fortunately or unfortunately - my finances will simply not allow indulgence. It's a shame - as those full length socket Everlasting chisels are beautiful prizes.