Heat Treating Thin Blades...

69_knives

69_knives

Joined
Nov 20, 2008
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Hi all, this weekend I should be ready to HT some thin blades that I've made and I do have a plan of action but wanted a little guidance to be sure that I'm not going to wreck or warp my blades.

The blades are just a hair under 1/8" thick, and about 1.8" wide x 8" long, going to be my version of an 8" chef knife.

My plan was to sandwich a blade between two pieces of 1/8" x 1" flat bar with the flat bar covering the spine portion of the blade leaving the edge half exposed to do an edge quench. Would this be adequate to keep the blade straight or is there a better way?

Steel is leaf spring 5160, using a gas forge to heat.

 
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i use alot of 3/32 15n20 and do not have a problem but with an 8" blade you could get some warpage
 
I've heat treated many blades a lot thinner than that, with no probs.

Just make sure the blades are normalized and don't over heat.

If you get a little warp, you have a couple minutes, right out of the quench to staighten.
I just do it with my gloved hands.
 
Making sure you agitate the blade in the quench spine to cutting edge instead of side to side has helped cut down warpage in my longer blades.
 
Well, it will be a nail biter for me I guess.

the 'sharp' edges are only about 1/16. I think I may play it safe and clamp the spine of the blade between the flat bar and heat the whole works up and quench the edge only.

Thanks for the replies.

I was planning on doing a couple more blades on the weekend but we're supposed to be getting -40 c/f windchill tomorrow... Wonder how many layers I can wear and still forge. :)
 
69_knives said:
Well, it will be a nail biter for me I guess.

the 'sharp' edges are only about 1/16. I think I may play it safe and clamp the spine of the blade between the flat bar and heat the whole works up and quench the edge only.

Thanks for the replies.

I was planning on doing a couple more blades on the weekend but we're supposed to be getting -40 c/f windchill tomorrow... Wonder how many layers I can wear and still forge. :)
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I'm no expert, but I would be worried about the heat the two pieces of flat bar clamped on the spine will hold for a long period. If I understand right, the flat bar will not go in the quench, just the edge. I think the heat from the flat bar will bleed down possibly doing weird things to the heat treat on the quenched edge. Just a thought.
I have made quite a few 3/32" kitchen knives from 1095 and have had minimal warping problems. Whatever you end up doing, let us know how it works out. Good luck.

-Mike
 
Nails are pretty well gone and I haven't even lit the forge yet. It's -4F/-20C right not without windchill but I'm still going to go git'er done.

What you mentioned about the heat from the flatbar hadn't crossed my mind yet so that may have been a 'woops'. I had thought of just quenching the whole thing and the slowed cooling where the flat bar would be would keep the blade softer.

Still haven't decided, I may just do it willy nilly and pray to Buddha. :)
 
AcridSaint said:
I heat treat all thin blades before grinding. If it's 15N20 it still warps :D
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i know i didn't mean to make it sound like that just giving a full description of what I use, but I have only had two blades to warp with it;), It snowed hear two days ago three inches maybe but I had forgotten what it looks like damn that stuff it cold in your boots
 
I grind all my knives to 1/32 at the edge. Just grind em evenly, normalize, and quench straight. Don't allow any side to side movement during agitation, and I think you'll be fine. Like Don said, if you pull the blade from the oil to check straightness once the blade is just barely vaporing off oil, you'll have a short window of time to straigten things out if necessary using gloved hands.

--nathan
 
Don't mean to hijack this thread, but what about a 3/32 small hunter/bird and trout blade that is about 3 and a half inches long, and an inch wide, made from annealed and precision ground O-1? Is that gonna warp pretty badly?

I had planned on making a slipjoint out of the steel but figured a hunter would be easier for my first couple knives. Should I grind the bevels first or just do it after HT?
 
So, all went pretty well.

I normalized twice and quenched twice.

The blades look exactly like they were before HT. The tang is a bit thin and narrow so I did have to straighten it a bit.

I was very busy, despite getting a late start. I found a place that sells used circular saw blades for $1.00 for 7" and $2.00 for 10" so I thought I'd play with those... man do those blades get hard.

One of the 7" drop point hunters is for my younger brother and the one with the aluminum scales is for my boss; shape and aluminum scales are his request.

 
hevy ev's said:
i know i didn't mean to make it sound like that just giving a full description of what I use, but I have only had two blades to warp with it;), It snowed hear two days ago three inches maybe but I had forgotten what it looks like damn that stuff it cold in your boots
Click to expand...

Hi - just to make it clear, I wasn't taking a shot at you with the 15N20 bit. I've got probably 20' of it in .095" and I've made many blades with it. I just did a pocket knife with a 2.5" blade and the bastard warped. Don't usually get so much that it can't be ground out (why I started heat treating them before grinding), but I sure get it.
 
Guess I was worried about nothing. Those saw blades, some were as thin as 0.065 and the one I made my boss' knife is now 0.050 after final grinding and polishing.

I polished everything up and made sure the pins were a good fit then cleaned with lacquer thinner and used 60 minute marine epoxy on both sides of the tang, put it together, squeezed together with vise grips near the pin I was going to peen and went at it.

This knife is by far the sharpest tool I've held in my hands :)

I cut the 4 flaps off a 15x15" box and proceded to cut through the corrugations on a slight diagnal, making about 120 cuts averaging about 7" and it will still push cut newspaper. Also earned a slice on the underside of my forearm...

The handle is a touch long; before I noticed that I didn't measure it I had already ground too far.

All shined up.


alum004-0.jpg


The mirror polished finish really shows minor scratching. maybe a satin finish will be better.

alum001-0.jpg
 
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FWIW, don't polish the whole tang. It may round the edges and make getting a perfect fit with the scales a problem.Flat sand it and leave it at 120 grit.Polish the blade and ricasso as you see fit. I like a matte finish .
Stacy
 
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