Tempering mistakes?

[Yankee Josh]

Hello all! I've filed and honed over a hundred axes and hatchets to date. So I've got a good handle on what a proper temper feels like under my file. In that time I've come across butter soft ones and really hard ones as well. But there are 2 that stand out as stupid hard. I'm wondering if they are mistakes? They must be brittle right?
My hrc72 Grobet file, while making steady and fairly easy progress on a good temper, struggles to file these. It will do it but just barely. So that must mean then that these axes are close to hrc70! 68-70 something like that I think.
One of them is a C. Hammond carpenters hatchet with an inlaid bit;




And the other is that Americanax side axe I got yesterday. I believe it's mono steel but I'm not a hundred percent on that.



On both the oxidation layer was by far the easiest part. It went downhill from there quick!
Do any of you have any that are the same? Just beyond ridiculously hard! And what do you think, mistakes in tempering?

 

[garry3]

Maybe a mistake but perhaps not that far off. You are probably over estimating their HRC hardness a little but ya I have come across a few that were hard on a good file. I suspect that hatchets can be harder than full size axes do to the stresses involved.
Those are great looking hatchets and have survived this long, I sure wouldn't temper them back. Hard is good, I love them like that.

 

[jake pogg]

I'd second Garry on that they're meant to be that way,and it is a good thing that they are,(though inconvenient;i have similar trouble with a my drawknives).

Carpenter's side-axe is not swung as wild as a felling axe,nor is it likely to encounter unpredictable densities or inclusions,knots,barbwire,fencing staples,pebbles...
.
It is a bench tool that lives in a clean environment of a wood shop,and i used on clean,predictable wood.

It is very unlikely that a mistake was made in HT.Quality control was darn good in the past,they looked for bad batches out of HT in particular.
Competition among US tool makers was stiff,they couldn't afford screwups.

If that hardness is consistent throughout i'd say it is deliberate and well warranted.
However,if such event(or the opposite,as in way soft)was spotty,in places,i think that'd be cause to suspect a potential problem.
(but that would not be straightforward at all,it can be HT,or material,or events in tools life,or...?......)
But consistent even hardness with 99.9% certainty = good.

 

[jblyttle]

Stones may be best for those.

 

[Yankee Josh]

I definitely wouldn't screw them up by messing with the temper! Like you guys said I'm glad to have them that hard.
And while I could be over estimating the hardness I don't think I am. I recieved a brand new inox file and it does the same as my older one. Even trying to put a micro bevel on either takes a lot more effort than you'd expect. A lot of pressure and repetition on only a 1/16" of steel. I'm literally shaking my head in disbelief trying to sharpen them! It's unreal! I keep wondering if it's just the outermost edge that's so hard and they may get a tad softer in a little ways. But I'll be damned if I can ever get there! I don't think that's the case anyhow. I have the best and hardest file money can buy and I can just barely get them filed.
For instance I was unable to file that C. Hammond hatchet at all until I got the Grobet file and even then I could barely do it. It stands to reason then that it's close to the files hardness.
Is it possible if they chose the correct composition of steel that they could be hardened to that extent without becoming brittle?
I wish I had thought to use my wet grinding wheel just to see how it would do. Seems like it would've been futile but maybe not?

 

[Fmont]

What kind of wheel is it? Like an old sandstone one? I would imagine it would work but a belt would be quicker. Then finish on stones.

 

[Fmont]

Hey YJ, I wanted to mention that Pferd makes Inox files, too. Their line is called corinox, they're a touchhh softer at 70hrc, but they make them in 10" lengths. Very nice, definitely on par with the Grobet Inox. Same as Grobet Inox, the downside is the price. They're yellow tanged, so maybe Grobet makes them?

 

[junkenstien]

What pattern is your file?

 

[Yankee Josh]

Swiss pattern 00 cut. Here's the unused side of my new one;
You may have heard me mention it before but it cuts every swipe but makes filings small enough that a rap on the bench clears it. I really can't recommend them enough. I'll never buy another new kind file again. I'll still look for older ones but seriously once you try one of these you'll never go back. $33 shipped from Amazon right now.
Edit; (this was not a paid advertisement)

 

[jake pogg]

Stones may be best for those.

I think this may be the long and the short of it...

Is it possible if they chose the correct composition of steel that they could be hardened to that extent without becoming brittle?

Composition,yes,and the type of HT,and also several things besides,all of which combined suited to the kind of work the tool is expected to hold up to.
In other words "Brittle" is a term strictly relative to aim in view.

So it'd probably not be prudent to change the angle to a finer one,or do work not consistent with the duty of a side-hatchet.
(I whacked a piece of moose meat with a big bone in it with my Handmade(darkening of reason)and mangled the edge very badly.....).

So one kinda hopes that the maker designed/produced/HT'd the tool while balancing all these factors intelligently.

Not being Any kind of authority on filing or sharpening in general but still I'd beware of filing something that so nears the hardness of the file itself;you can bend or break the tips of file teeth...

And just for giggles,I did happen to think of a metallurgical event that could result in overly-hard edge,something that may've been missed by quality control of manufacturers in the past.
It is the effect referred to as the "retained martensite".
The Quench,that part of process that achieves maximum hardness mat'l is capable of,most commonly involves converting the structure in one type of martensite or another,with subsequent Tempering that dissolves some of that hard/brittle structure which adjusts it to avoid excessive hardness .
In some alloys/under some circumstances the Martensite will keep on forming even after the tempering cycle,so only what Martensite was already formed gets tempered.
It can be happening for quite some time after tempering,and so of course much of the blade will contain Untempered Martensite.
To counteract this effect the Cryogenic treatment is used nowadays,and i'm not sure just how far that process goes back to historically...


But i'd still incline towards the first version of events anyway,that such degree of hardness was deliberate.