1095 Not Annealing

[Bill Reinicke]

I am a new knife maker. I got ahead of myself and heat treated my blades before I drilled holes for the scales. I did a great job heat treating but now I can't anneal the blades to be able to drill them. I have tried several normalizing sessions. I have taken the blades to critical temp an allowed to cool very slowly. It doesn't seem to matter what I do, it almost seems like these blades are only getting harder. I am using a forge so my temps are estimations at best and am mostly going by sight and color of metal. I took a few of the blades and let them soak at critical temp for about 15-20 minutes before letting them slowly cool. The blades seems even harder. The file still skates across it like it did after the quench for heat treating. Any ideas?

[Ted Stocksdale]

To drill holes in the tang, I just heat the tang with a small torch until it turns just begins to turn the slightest bit red - you want to stay well on the cold side of critical. Best to have the blade in some sort of heat-sink so the heat doesn't travel up and ruin your hardness, though. This is really just a super-high-temperature temper, but it will knock the hardness down far enough to drill even with stubborn stuff like O1 as long as you have a good sharp drill bit. I like cobalt bits, they're a lot sturdier than pure carbide and I can re-sharpen them with my Drill Doctor. 

[Bill Reinicke]

Thank you. I appreciate the info. Do you let the metal cool slowly. No quench, correct?

[Ted Stocksdale]

I always let it cool on its own, just sitting there

[Alan Longmire]

1095 is bad to do that.  Books tell you to soak and slow cool, but that just creates sheets of carbides that can't be drilled.  In the future, don't soak for any length of time, and do a subcritical anneal by getting it to a low red and cooling to black in still air.  This isn't as soft as a true anneal, but prevents those sheet carbides. 

[Will Robertson]

Thank you to @Bill Reinicke, @Ted Stocksdale and @Alan Longmire for this discussion - it's very interesting for me to read about this and learn - I hadn't known that carbide sheets could form like this and it's very good to know about other folk using the tang temper technique.

[Alan Longmire]

I learned the sheet carbide thing from Kevin Cashen, the only knife guy I know who's so into metallurgy he bought an electron microscope .  He was experimenting with O-1, but all carbon steels at around 1% carbon and up will do that if you fully dissolve the carbides at heat and cool in the forge or in a bucket of vermiculite or something.  To get the desired spheroidized carbide structure the "slow cooling" specified is like 50 degrees F per hour, and that requires a controlled furnace. 

 

The subcritical anneal gives a mixed carbide structure, but at least it can be drilled and filed.  The overtempering Ted mentioned works fine too, and is pretty much required to drill some steels.  

 

Jerrod will be able to tell you much more, if you're interested. 

[Joël Mercier]

I believe the critical temp +slow uncontrolled cooling is called a lamellar anneal. Just to put a word on it 

 

I've seen a lot of puzzled new and not so new makers unable to drill their 1095 on FB. Everytime I explained what was happening they wouldn't believe me. 

 

Like others said, just normalize and air cool. 

 

Btw, if metallurgy applied to knife steels interests you, you should buy Larrin Thomas' book. Plenty of useful info in there for quick access. 

Edited April 25 by Joël Mercier

[Bill Reinicke]

I want to thank you guys for sharing your knowledge. I was able to anneal my blades and drill the handles. This was an interesting experience. I learned a little more about heat treating and knife making.

[Doug Lester]

If you learned something then you had a success.  Good going.

 

Doug