Hardness testing - there's GOTTA be a better way....

I got this set of hardness testing chisels (kiridashi) from Matthew Parkinson (Dragon's Breath Forge) last year and I like how they've been working so far. I'm able to easily get a reading within 1-2 points. They are professionally heat treated A2. He has a video on his youtube channel on how to use them.

These are especially nice for shallow hardening carbon steels since they test the actual cutting edge of the blade, as opposed to the ricasso, which may not even get quenched depending on the heat treat. This set of 56, 58, 60, & 62 HRC chisels was $125. He also sells a set of 58-64 for the same price. Or you can pay $225 for a set of 50-64 chisels. You can also get one of the first sets to start out with (which I did) and if later on you decide you want a larger range you can get an upgrade for the full set for another $125. (At least this was the case at the time I purchased them)

Here are a couple of pictures:






~Paul
My Youtube Channel
... (It's been a few years since my last upload)
 
kuraki said:
Do you just scratch with them then?
Click to expand...


You see which chisels will and which one's won't shave (or dent or cut into) the steel off the the cutting edge.

This is just one way to go about it (which is a bit of back and forth), but let's say I'm shooting for 60 HRC. After my first temper I'll start with the 62 chisel, which usually will shave a bit of steel off of the edge. Then I check 58 to make sure it's harder and that it won't cut into the knife's edge at all, but instead leaves a slight mark/dent on the chisel's edge.

Next I'll go to the 60 HRC chisel and do the same. If it doesn't quite or just barely begins to cut into (or mark/dent/ding) the edge I will then "reverse their roles", so to speak, by using knife's edge to see if it will do the same to the chisel, and if they both equally, hardly shave/dent each others' edges, I can assume the knife is at about 60 HRC. However, if the knife does not equally dent/shave the edge of the chisel the same way the chisel did to the knife, I can assume that the 60 HRC chisel just slightly harder and the knife is about 59HRC.

I apologize if this sounds confusing, but it really isn't, I'm just not the best when it comes to explaining things or summing them up lol. Check out the "Dragon's Breath Forge" youtube channel and there is a vid from a couple yeas back where Matt describes how he uses them, although you'll have to turn the volume way up as the audio isn't that great.

There is a little bit of a learning curve when first using them, but you'll find it's actually pretty intuitive. It's obviously not as precise a reading that a real Rockwell tester will give, but it's pretty easy to get within 1-2 points.

The chisel's can been touched up on a stone after every few uses or however often they need to be. I just wait until there aren't any fresh areas of edge to test with before I do. You want to use water or oil on your stones though instead of a belt grinder or even dry sandpaper (or dry diamond plates in my case) just to be safe to keep them generating any heat and loosing any amount of temper and to avoid any possible "surface annealing" (I believe is how Matthew referred to it) so you don't any "false readings". Not sure how easy it is to do so, but I find it easy enough to spay some water on my diamond plates and it can't hurt 'em.

~Paul
My Youtube Channel
... (It's been a few years since my last upload)
 
coldsteelburns said:
I got this set of hardness testing chisels (kiridashi) from Matthew Parkinson (Dragon's Breath Forge) last year and I like how they've been working so far. I'm able to easily get a reading within 1-2 points. They are professionally heat treated A2. He has a video on his youtube channel on how to use them.

These are especially nice for shallow hardening carbon steels since they test the actual cutting edge of the blade, as opposed to the ricasso, which may not even get quenched depending on the heat treat. This set of 56, 58, 60, & 62 HRC chisels was $125. He also sells a set of 58-64 for the same price. Or you can pay $225 for a set of 50-64 chisels. You can also get one of the first sets to start out with (which I did) and if later on you decide you want a larger range you can get an upgrade for the full set for another $125. (At least this was the case at the time I purchased them)

Here are a couple of pictures:






~Paul
My Youtube Channel
... (It's been a few years since my last upload)
Click to expand...
Very cool. I may just need to make a set of these for myself. Any idea why they are A2 steel? Would just about any steel that can be hardened high enough work?
 
Busto said:
Call the Local Machine Shops to find one with a Hardness tester and be polite and show up with a couple Burritos and ask if they can test your blades....Even if you have to pay a small amount to have a handful of blades tested you can begin a working relationship that over time may just cost a Burrito. I do this with a local steel supplier and bring extra burritos and walk away most time with what I was looking for at the cost of the food....OR
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this makes the most sense. the Local Machine Shop pays to have the tester calibrated every 6 months, have the calibration blocks replaced on a regular basis, and maintains all the logs and records.
 
Maybe they do. If they're ISO they might. I doubt most of the variety that accept walk in-work do.
 
most machine shops locally work mostly for large multinational companies or their suppliers, they have to be ISO to get any work. one has to be careful of test blocks, some are sold that are +/- 3 points, even the most expensive are +/- 1 point. So we could have same tester, same cal block, and test the same blade, have a difference of 2 HRc, and both be right.
 
The barefoot boy said:
Very cool. I may just need to make a set of these for myself. Any idea why they are A2 steel? Would just about any steel that can be hardened high enough work?
Click to expand...

I'm really not sure why he chose A2. Perhaps it might have something to do with its edge holding characteristics so that the chisel edges would last longer than the low allow carbon steels they're (I'm sure) most often used to test. I haven't really thought about it since I've received them, though.

FWIW, I ordered mine from him over FB messenger so I was able to ask him a few quick questions.

~Paul
My Youtube Channel

... (It's been a few years since my last upload)
 
The barefoot boy said:
Very cool. I may just need to make a set of these for myself
Click to expand...

I'm confused. If you can make these at such precise hardness why do you need them?

I guess my only question is after reading post after post daily of reaching the full potential of such and such steel using precise heat treat with DI or Sub cooling why would someone not want their own precise RH tester? I get sending them off and had done "professionally" but I've been around the block or two and seen sometimes having professionally done doesn't always mean professionally done. I myself I just want to be in total control of my knife building totally myself. For that means having my own Rh tester.
 
LCoop said:
I'm confused. If you can make these at such precise hardness why do you need them?

I guess my only question is after reading post after post daily of reaching the full potential of such and such steel using precise heat treat with DI or Sub cooling why would someone not want their own precise RH tester? I get sending them off and had done "professionally" but I've been around the block or two and seen sometimes having professionally done doesn't always mean professionally done. I myself I just want to be in total control of my knife building totally myself. For that means having my own Rh tester.
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I meant I would make the kiridashi and then have them heat treated at Peters. Just until I can afford a HT oven.
 
LCoop said:
I'm confused. If you can make these at such precise hardness why do you need them?

I guess my only question is after reading post after post daily of reaching the full potential of such and such steel using precise heat treat with DI or Sub cooling why would someone not want their own precise RH tester? I get sending them off and had done "professionally" but I've been around the block or two and seen sometimes having professionally done doesn't always mean professionally done. I myself I just want to be in total control of my knife building totally myself. For that means having my own Rh tester.
Click to expand...

FWIW, I'm pretty sure Matthew said it was Peter's HT that Heat treated these chisels. I had asked him about it before I bought them as well as if each chisel was individually RC tested. IIRC, he said that they tested 10 of each hardness for each batch.

Again, these are nice for testing carbon steels, especially those which are shallow hardening and/or if the blade is differentially hardened where only the edge might reach full hardness. I use my forge to heat treat my knives so they work fine for my needs.

I basically see them as simply being a better option than hardness testing files (don't they also only come in 5 point increments?), since I can't quite afford an actual Rockwell tester, or a heat treating oven for that matter. That being said, I personally have always enjoyed the ABS' style and way of making knives, which are heat treated in forges all the time and work great. :thumbsup:


~Paul
My Youtube Channel
... (It's been a few years since my last upload)
 
While we are on this subject, can someone provide a methodology for using hardness testing files and general guidelines for what one can conclude. For example, I have the Tsubosan file kit. Each file is named 55, 60, etc, and there is a chart that gives the range for each. The blue 60's range is 60-62. The black 65 one has a range of 64-66.

How hard do you push with them? Where on the knife do you try this?

If the Blue one (60-62) skates, but the black one (64-66) scratches just barely, what is the conclusion? What if it scratches easily?

Is the best one can say that the blade is between 63 and 66?
 
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