Are you putting clay on the whole blade, or just the spine? If you're putting thick clay on the whole blade it will never fully harden. For 1075 try 1475.

Kevin for 1075, use 1475 and parks 50. Can you use water? Yes, but it can cause issues like cracking. The ASM guidelines are for industrial applications like rounds or cubes or spheres. Personally I think your clay was too thick.Clay thickness should be 1/16" or less. Keep trying.

Brion

Also make sure you have correctly performed reducing heat thermal cycling after forging. You do need to get that grain structure repaired and the carbon properly dissolved/dispersed for hardening. A good tight grain is less likely to chip/deform, as well.

There are numerous factors besides temp and quenchant that effect hardening - especially with clay.

I might also add something - flex is determined by geometry. .260" - .300" is pretty think for a performance knife. (Think thin to win. You're not trying to win a cutting competition. Chopping time is not a factor.)

I realize I'm only rated as an apprentice, but I have made two performance blades that passed a Journeyman equivalent test. I echo what Karl is recommending regarding thickness. At the spine mine were both under 0.20 thick (one at 0.18" and the other at 0.19). Still had to put a 4' section of pipe on the handle to get them to bend 90 degrees, and I leaned on that pipe hard!

I would like to also humbly suggest that you lose the clay and do a full hardness quench, double temper, then draw the spine (blue-back) with a torch. This process was successful for the 10 performance blade tests we did in the ABS intro class I took.

(This is more asking questions then arguing and may be a bit random to fallow) My clay HT method is 3-4 cycles cooled to black then back in forge, clay, quench, 2 rounds temper 430F. During temper i reasontly i started quick cooling a blade by dunking it into water between tempering cycles.

OK as i understand it water is better for a thicker piece of 1075 because is shallow hardening do to the fact that it does not have enough manganese to aid in hardening. also, I can't really do bend tests in my shop right now because i made a bad stand for my post vise. However, with coronavirus quarantine, I have time to do some blue backrests. will do some comparisons once i get a new stand made.

Also i have no clue were to even get 1475 and did not want to use a deep hardening steel for the test.

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Also i have no clue were to even get 1475 and did not want to use a deep hardening steel for the test.

Pretty sure he meant to heat the 1075 to 1475 deg. F for the hardening pass. We used 1084 for our "test" knives.

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Pretty sure he meant to heat the 1075 to 1475 deg. F for the hardening pass. We used 1084 for our "test" knives.

ok, that makes so much more sense as I was thinking it was an alloy. hopefully, my jury rigid thermal couple prob will work or I will need to get a new multimeter as I only have 1500F and 1900F tempistick as I can't find one compatible with my current multimeter. may end up switching to 80crv2 or 52100 as I have these in stock that in stock right now and I would rather save my 1095 for cutlery.

also, I am making a thicker blade because it has more mass which ads more omph to the chop...however I also could not really do a lot of chopping tests as my car breaks went out and have them fixed now so time to experiment with blue backing. Good things come to those who wait and well I want that piece of paper that says I passed the ABS shop performance test because it's something that is quality control and about a year and a half into my bladesmithing careers I decided I would not sell any more blades (i had sold 2 via commission to my mother and plan to actually return that to her) till i had gotten that paper as its acts as a quality control device. I also got much harsher on my self-judging of my blades around the same time. time to sacrifice some steel to the Goddess testing.

Side Note: I likely am over claying the blades for the test, but I am also being cautious with the test and i think i likely use a thicker mixture of clay than others. I have enough steel left that I can reheat treat the current blade so I will give a thinner coat a try. however, I know from experimentation that deep hardening steels need a thicker coating then shallow hardening. i have mostly worked a lot of salvaged ford leaf spring during my 3 years and 9 months of smithing i hade a very small budget for supply.

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may end up switching to 80crv2 or 52100 as I have these in stock that in stock right now and I would rather save my 1095 for cutlery.

If I may throw my thoughts in here for a second, I would suggest using a steel you know well for your test blade. Use a steel that you have the HT dialed in and can accurately predict how it will function after the processes.

The way I see it, the performance test is one of knowledge. It tests the smith's knowledge of the steel and the HT process for that steel, when trying to achieve a specific result. So use something that you already know well.

I chose to contact Kevin Cashen about this before i commented again and terns out with the simple 10xx series which is a series i do have a good deal of experience with and it turns out that if you have a blade that's 5/16ths or thicker you cant get a threw hardness on them even parks 50 and require water, as my calipers were dead and also did not have good battery life, in general, i checked the blade thickness with a less scientific method using a mostly empty Irwin's drillbit set box and the blade is almost 5/16ths of an inch wide, and with the clay added it definitely was over 5/16ths of an inch. so it turns out you do need water. i have used clay enough to know the signs to let me know I won't auto temper and i have had some cross confirmation on a second method of knowing when your blade has fully hardened with clay on page 176 of the book The Art of the Japanese Sword: The Craft of Swordmaking and its Appreciation that if your clay is intact over the entire blade, the blade did not harden, and this makes sense given that the creation of martensite happens at the speed of sound which is why you can hear a noise as the blade hardens if you listen. so now I know i need to use water when making a very thick blade using 10xx series...which is helpful as i plan on making a buddy a kukuri in the future and as those are differentially heat treated via a unique old school edge quench that I cant do as i do not have a charcoal/coal forge at this time i have to achieve that via clay.

the other trick/indecator that your blade will not auto temper with clay is you wait for your quench medium to stop boiling as that will indicate that the entire piece has cooled.