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Symptoms of a bad heat treat?

HeavyHanded

HeavyHanded

Joined
Jun 4, 2010
Messages
6,642
As the title says, I'm wondering what are the most common indicators of a poor heat treat. This might be the wrong forum, by I'm primarily concerned with how it effects edge holding, burr formation, and related issues.
 
since i sharpen on the paper wheels, the first thing i notice if a blade is too soft is how grabby the blade is on the grit wheel. the blade tends to get pulled up the wheel. it forms a burr real quickly and the burr sometimes takes a while to get rid of on the slotted wheel with just light pressure (on some knives with a good ht, the burr can be hard to get rid of due to toughness of the steel and more pressure is needed to get rid of it on the slotted wheel).

its like trying to break a paper clip by bending it back and forth compared to a harder piece of steel which would break within a few bends due to it being harder.

as for edge holding, i'm sure most of us know that a blade with too low an rc hardness will not hold an edge long.
 
I recently tousled with a knife that's in 12c27n. I have a Bark River using the same steel and its a great performer, takes a great edge at any grit with very little fuss and holds it well too.

The current knife (mfg to be unidentified) gave me nothing but trouble, and the jury's still out on edge retention. It was OK to grind on the stone - after cleaning up the factory bevels I always assume there'll be some issues until all the original apex metal is removed. In this case the burr was an absolute nightmare to remove - flips of twenty or thirty passes needed to reduce it and it still wouldn't go away. Finally had to scrub it off with a bit of pressure on a loaded strop and then lightly touch it back up on the stone till the apex was crisp again. I don't have a lot of hope for the longevity of this edge - time will tell. One things for sure, the heat treat or integrity of this batch compared to the Bark River fare is night and day. Manufacturer has a good if not exceptional reputation. The success rate for returning a knife under these circumstances cannot be good - maker is overseas and I can't imagine a retailer accepting a return for something as subjective as this.
 
yeah 12c27 in the mid 50hrc is a pain in the *ss to deburr. but that's not exactly what i'd call "bad heat treat", it's not defective, it's like that because they want it soft so the average user can beat it on a butchers steel , do all kind of stupid things without breaking the blade etc ...that's a pain for everyone else but i understand their logic.

unfortunately that's the logic most french/european maker use for their traditional french/european patterns, i have a couple laguioles from reputables makers that are otherwise very well done and finished but that i barely use because of this. otoh stainless opinels have a very good rep and they use the same steel, probably harder.
 
I'll 2nd the comment regard Opinel's stainless blades (12C27M). Excellent stuff; Sandvik specs it up to HRC 59 or so, and I think Opinel took advantage of that. I thinned mine to a zero-bevel edge (convex), and it's a slicing demon that has held up well. I gave the same treatment to a carbon-bladed Opinel at the same time, and the carbon blade, although it has taken a wicked-sharp edge, seems noticeably softer (deforms more easily if too much pressure is used on the strop, and dings easily if bumped into something hard). Haven't noticed the same issue with the Sandvik stainless Opinel; it seems to hold it's thin edge better. Side-by-side, they seem equal in hair-popping & slicing abilities (both fantastic). I would've expected that from good ol' carbon steel. But, from the stainless blade, that's quite impressive.

Regarding sharpening it, I didn't have many issues with burrs/wires either (another reason I really like the stuff). I sharpened mine on wet/dry sandpaper, up through 2000+ grit, plus stropping on either of Simichrome or 1 micron diamond paste on balsa and/or leather. Lately doing the same with diamond paste on red oak, with even better results.
 
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pwet said:
yeah 12c27 in the mid 50hrc is a pain in the *ss to deburr. but that's not exactly what i'd call "bad heat treat", it's not defective, it's like that because they want it soft so the average user can beat it on a butchers steel , do all kind of stupid things without breaking the blade etc ...that's a pain for everyone else but i understand their logic.
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This knife is from a Scandinavian mfg and its supposed to be RC 59 or so. I expect some trouble with the lower RC, but this is making me very suspicious. I also had to take this edge up to a fairly high polish to get good cutting results, so that doesn't seem to jibe well with my experience re mid 50s RC on any knife, nor my past experience with this steel as done by Bark River. Entirely possible that this is normal for this steel utilizing EKA's heat treat (said I wasn't gonna and did it anyway) and I'll be enjoying the fruits of my labor for a long time without having to touch up this particular specimen. My gut feeling is the fizz won't last long and I've got a relatively expensive tool box knife. Time will tell - camping season (for me) starts in 8 weeks or so...
 
Now that the maker is known I'll second the too soft thought. If its a M2K and you are not using a microbevel I applaud you for making it burr free.

It's also a razor steel so try using your 4k and a bit of stropping with a fine compound.
 
Had same experience wih a SAK OH Sentinel. It's lacking the durability of my other SAK. They offer a replacement, but I simply raise the edge angle (40) following their recommendation. Usable, but not to my saisfaction ;)
 
hh, i would like to check out this knife. would you mind sending it to me? i would like to see what happens when i put it on the slotted paper wheel with the edge you have on it now.
 
knifenut1013 said:
Now that the maker is known I'll second the too soft thought. If its a M2K and you are not using a microbevel I applaud you for making it burr free.

It's also a razor steel so try using your 4k and a bit of stropping with a fine compound.
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Not sure what an MK2 is, but this knife (EKA H8 Nordic Hunter) absolutely demands a more refined edge. I actually took it up to 6000 JiS and then dropped back down to 4000 and had to finish it off with compound. Right now it has a nice edge - if it holds up I'll be very happy. Any steel that can hold onto a burr like this and take a refined (albeit toothy-feeling) edge just might be able to hold onto it for a long time. Its a strange combination of characteristics compared to my other knife with this steel, they don't seem to be the same animal at all. Even at 6000 grit and stropped on newspaper it felt pretty toothy.
 
richard j said:
hh, i would like to check out this knife. would you mind sending it to me? i would like to see what happens when i put it on the slotted paper wheel with the edge you have on it now.
Click to expand...

Richard, thanks for the offer. I believe I'm going to beat it up a bit and if I still have any concerns I'll happily take you up. This wouldn't be the first knife that gave me a lot of trouble with bur formation and turned out OK, but it would be the first with this steel in this RC that did so. Probably should have hammered on it before making this thread, but wanted some input from the experts.
 
Heat treat also includes the tempering cycles, so poor HT could also include little or no tempering. This makes an edge brittle and prone to chipping.
 
I've noticed very stubborn wires like that on some others as well. Oftentimes, on VG-10, ATS-34 and Case's Tru-Sharp (420HC, also at pretty low RC). I really believe Case's Tru-Sharp gets an undeserved knock sometimes, by a perception of their edges dulling easily. I'm convinced much of that is due to the wire edges, which are very tenacious and will make the blade seem to dull quickly when the wire rolls over. Once the wire is cleaned up though, the Tru-Sharp holds up pretty darn well, better than the published RC numbers might imply (mid-50s). It seems to make sense, that if a steel can stubbornly hang on to a wire edge so well, the steel behind the wire edge ought to be very stable & durable too.

HH, your comment on the highly refined Sandvik edge still feeling a bit toothy, echoes what I've noticed on the Opinel I mentioned earlier. I test my edges by slicing phone book paper, and this one has a pretty aggressive 'toothy' sound to it, in slicing through the paper. Sandvik's process is claimed to produce a very fine grain in this steel, and I believe it, in seeing how fine the edge gets. And yet still, it seems to have that 'bite' to it. Good combination.
 
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