Should I Re-temper 1095

[ScarFoot]

I’m making some small edc/hunting/skinning knives out of 1095 and they all came out of temper around 63 HRC. The knives have approx. 3” blades and I grind them down to a thickness between 0.10” - 0.075”. They also have clay hamons. I feel like they need to be closer to 60HRC for their intended purpose but am thinking about leaving one as is for personal use/testing.
What do y’all think? Should I temper them down a bit? I ran them at 405 degrees F to get them where they are now. The picture below is one I made out of W2 a while ago to give you an idea of overall size and blade shape.

 

[Stuart Davenport Knives]

I temper all of my hunters to at least 63HRC regardless of steel type.

 

[Stacy E. Apelt - Bladesmith]

What you have sounds perfect to me. Properly quenched and tempered at 405°F should be in the low 60's. IIRC, I get Rc62 with my 400° tempers.

 

[ScarFoot]

What you have sounds perfect to me. Properly quenched and tempered at 405°F should be in the low 60's. IIRC, I get Rc62 with my 400° tempers.

I was a bit surprised they consistently hit 63 but I checked the tester with the cal blocks and it was spot on. I got around 61 last time I used 1095 but I put my quench tank in a water bath this time to keep my oil temps from running away. Maybe that made the difference?.?. I was using parks 50 and held my oil temp around 90 degrees. The blanks were heated to 1465-1470 degrees F pre-quench.

FYI, These are the same blanks that I posted about a couple of months ago that failed to harden when I coated them with atp-641. They got hard this time.

 

[Stuart Davenport Knives]

Sounds then like your coat of ATP was too thick. Just a very thin wash is all that is required when heat treating low alloy steels. Moving up in temp, say like A-2 temps, the ATP needs to be a little thicker.

How did you prevent decarb on this go around?

 

[ScarFoot]

Sounds then like your coat of ATP was too thick. Just a very thin wash is all that is required when heat treating low alloy steels. Moving up in temp, say like A-2 temps, the ATP needs to be a little thicker.

How did you prevent decarb on this go around?

I didn’t coat them this time. Just ground everything again. Fortunately I had enough meat left to work with when I got done I should be able to salvage most/all of them. I used a very thin coat of atp-641 the first time I heat treated them but it was the first time I’d ever used it so I wasn’t sure how thin it can get. I’m going to mess with it a little more on some 80CrV2 to see if I can get it thinner still. I used it on some 80CrV2 earlier and had great results and no issues with hardness. I did a batch of 1095 and W2 the same day and neither hardened properly.

I just retested the W2 today and a couple still failed hardness testing so I think something was up with that piece of steel. That’s after eliminating every variable I can control. Two or three blanks each have spots that are 45HRC, spots that are 63HRC, and everything in-between and I’m confident I’ve ground through any decarb. I’m fairly certain the blade/edge areas are hard but not confident enough for anything beyond personal use so I might finish them later this year just for practice and use them around the house. I’ve been wanting to try some different wood varieties that I got for handles so they’ll be good for that anyway.

 

[Stuart Davenport Knives]

Also, remember that some of the carbon steels from NJSB have had issues with heavy annealing in the past. Guys who forge don't notice heat treat issues because of the high heats of forging that break up those coarse carbides due to the heavy annealing process from that particular mill in Europe. Guys who do stock removal found out that a very high normalizing heat was necessary to get those steels to harden properly, especially the shallow hardening steels like W2, 1095, and to some extent even 52100. Also another variable, especially with shallow hardening steels, is over cycling the steel, making it so shallow hardening it won't harden properly unless a water or brine type quench is used. Failure to harden won't be due to the ATP-641 if applied properly, it's some other variable.

 

[ScarFoot]

Also, remember that some of the carbon steels from NJSB have had issues with heavy annealing in the past. Guys who forge don't notice heat treat issues because of the high heats of forging that break up those coarse carbides due to the heavy annealing process from that particular mill in Europe. Guys who do stock removal found out that a very high normalizing heat was necessary to get those steels to harden properly, especially the shallow hardening steels like W2, 1095, and to some extent even 52100. Also another variable, especially with shallow hardening steels, is over cycling the steel, making it so shallow hardening it won't harden properly unless a water or brine type quench is used. Failure to harden won't be due to the ATP-641 if applied properly, it's some other variable.

I’ve only been making a few years and don’t have a high output so I hadn’t heard that about the NJSB steel. Thats good info. I do stock removal and heat treat in an oven so I didn’t normalize the steel. The last pieces of 1095 and W2 I got before this batch were fine so it’s been a head scratcher. I broke several pieces of the previous batch and the grain looked great after I dialed in my soak times. I really didn’t think the ATP-641 could have caused the issue as thinly as it was applied but that was the only change to my process on this batch. Now it’s obvious that wasn’t the issue or not entirely anyway.

 

[Stacy E. Apelt - Bladesmith]

Are you SURE you ground all the decarb off the blades post HT. Many use a coating, like your ATP, and assume the blade is ready to finish. You will often still have decarb spots. Take those blades with the soft spots and grind them down well at 220 grit then take to 400 grit and test again.

A trick to see if there may be decarb spots on a blade is to dip it in FC after the first grind. If there are any light gray spots there is still decarb.

 

[ScarFoot]

I’m sure I’m through the decarb. I ground between 0.015-0.020” off per side after the first run just to get everything straight/parallel/pretty and probably 0.030” total per side off after the second run. After that second heat treat I took about 0.012”-0.015” per side off first and checked hardness and after finding soft spots I assumed decarb to be the culprit and ground another 0.012-0.015” per side off and checked again with similar results. I can’t grind them down any further and have anything usable at this point.

All were surface ground to 400 grit, checked for flatness on my surface plate, and checked for parallel with a micrometer before hardness testing. On the ones with soft spots I hardness tested both sides and confirmed the spots ran through the blank. The indentions left by the tester were also visibly deeper so I know it wasn’t a bending/flexing issue while testing.

There’s something else at play here that I haven’t been able to identify. I might break one and take a look at the grain just out of curiosity.

It’s only a couple blanks in question so it’s not the end of the world. You can’t win em all and it’s the little mysteries like this that keep it interesting anyway.