Knifemaking and other cool hobbies...

[Turtle]

___On further reflection, it occured to me a variation in thicknes may cause the uneven heating & so a buckle. If so, the location of this thickness variation likely occurs in the center of the buckle, one of the ends of the buckle, or a distance from either end of the buckle that is a multiple of half the entire width of the buckle.
___

[C1ay]

I recommend you visit the Knife Network. They even have a Heat Treating and Metallurgy forum. I suspect someone there will be familiar with your dilemna...

[Boerseun]

Thanks, Turtle & C1ay.

I've spoken to a couple 'o guys on the net, and most of them say "Yes, buckling is a bitch", but can't seem to pinpoint the exact cause.

I've got my own pet theory, and that is uneven cooling.

Differing thickness will also do it, as Turtle pointed out, but the blades are planed to a pretty level thickness. Moving the knife around in the kiln won't do - my kiln is an upright in which the knife is suspended from a special hook, and the element is coiled around it. So the heating is pretty even. It's the cooling that's bothering me now...

And one out of, say, six or seven blades buckles, from the same sheet of steel. So I don't know wether it is impurities. C1ay - can't remember whether it was you or nkt mentioning salting to remove impurities - what's that all about?

[C1ay]

Originally Posted by Boerseun

C1ay - can't remember whether it was you or nkt mentioning salting to remove impurities - what's that all about?

Gahd mentioned that from one of the books he's reading....

[nkt]

Salting only applies if you are actually casting the metal from a melt. You salt the melt to get some of the crud out of it.

Boersun, you didn't tell us what the buckling was like? Is it that the center remains in contact, and the ends curl up?

[Boerseun]

Hi there

The buckling is very subtle, actually. I probably made it sound a heck of a lot worse than it is. For instance, a Bowie knife I made recently warped with about 4mm. That's to say, if you put it flat on a level surface, the middle of the blade stands out about 4mm from the two tips thats lying flat on the surface. You can whack it out on an anvil, but the problem is that wherever you hit it, the metal becomes compressed and screws up your acid treatment when you try to get patterns out of it. It can be sorted out for knives, but with the sword I'm planning on making, the buckling will be much more pronounced.

[C1ay]

Originally Posted by Boerseun

You can whack it out on an anvil, but the problem is that wherever you hit it, the metal becomes compressed and screws up your acid treatment when you try to get patterns out of it.

Have you tried using a softer hammer to whack it out with, brass or even rawhide?

[Boerseun]

Got it sorted out!

Turns out that if you do a hollow grind on one side of the blade, and flip it over to do the other side, the grinder belt has worn off some. So - in effect, the flip side is ground with a second-hand belt, needing more pressure on the steel, thereby generating more heat and causing more stress to build up in the steel. And then, when you chuck it in the kiln for heat-treating, the stress is relieved by causing the blade to buckle!

What I'm going to try in the sword is to take two new belts, and dedicate a belt to a side. Every time the blade is flipped over, I'll use the other belt so that the heat builds up roughly equally on both sides, minimising the uneven stressing.

Gonna build my kiln now!

[Chacmool]

Congratulations! What materials are you using to build the kiln?

[Turtle]

Originally Posted by nkt

Salting only applies if you are actually casting the metal from a melt. You salt the melt to get some of the crud out of it.

___As I said my casting experience is with non-ferrous metals; the salt I used is borax, we call it a flux, & the crud we call slag.
___Great news Boerseun; any chance of you favoring us with a photo of one of your blades? The acid patterning you mention sounds intriguing.