HT and Curvature in Long Blades

[Rick Marchand]

What is the deal? When I want an upward curve I get a downward dip. When I want a dead straight blade I get an upward sweep..... argh!!!

I am using a vertical 6"dia x 36" tank with Houghton Quench K.... 1084 or 5160 mostly. I take my edge down to .040 prior to HT. Everything gets properly normalized and set up for the quench.

Am I missing something that would give me predictability in curvature? I've only recently gotten into blades over 10-12"


Rick

 

[Rick Marchand]

It's been a couple days with 70+ views...... nobody can help me out here?

Is the only way to control curvature by using clay coating? Why would some curve up and some curve down. Is it because I switched from a horizontal tank to a vertical? It seemed to be pretty consistant at first.... the tip would dip down a bit on the longer ones... probably just more noticeable.

When I used to edge quench it would curve up... that, I understood. I now fully harden the entire blade.... I figured it wouldn't curve at all. Is it because there is more mass at the spine... meaning more expansion?


Rick

 

[Justin King]

This is one of those parts of HT that you don't hear mentioned very much, although I have struggled with it myself. I only ever had the point drop when quenching in oil and just learned to try to predict it and leave a little extra width near the tip. I do not recall this being an issue with the last few blades I have made though.
Are you using an oven or forge for your HT?

 

[Kevin R. Cashen]

Let me guess your blade shape for you- longer than 8" (as you already mentioned) very simple shape, like a dirk, so that if it even has a clip it is a fairly simple to shallow one. The width is perhaps 1.5" wide or less and not much more, and the grind is a very simple "V" cross section from a flat grind, or a very subtle convex. This or at least this shape has given you the worst problems.

I have typed a detailed explanation for this so many times my fingers won't obey anymore, but you can lessen your problems with these blade shapes in oil by horizontal, spine first, quenching. 10XX will be the worst, but even O1 will do it in these shapes if your quench speed is out of synch enough.

 

[Rick Marchand]

...I have typed a detailed explanation for this so many times my fingers won't obey anymore, but you can lessen your problems with these blade shapes in oil by horizontal, spine first, quenching. 10XX will be the worst, but even O1 will do it in these shapes if your quench speed is out of synch enough.

Thanks Kevin..... where where where? I found passages where you mention quenching spine down. That cured the little twist I would get in the last few inches of the tip. My horizontal tank will not quench more than 16" OA.... so for longer blades I am stuck with the vertical tank. If I put a pre-curve toward the tip will it end up S-shaped? Maybe I should harass Wally to use his long tank for my larger blades. PITA

Rick

 

[Rick Marchand]

It took a lot of searching but I found it! Woooh-hoooo! Do you realize how many threads/posts contain the words.... heat treat + curvature + downward + warp + sweep + sori ? Talk about a needle in a haystack!

This kinda sucks now..... I built my vertical quench tank specifically for longer blades. BAWLZ. I knew about expansion but never put it together with the "anchoring" factor. I just saw it as the edge would harden first causing the upward curve and then lock it in. That's the difference between learning the individual components vs. understanding the process as a whole.


Thanks to the folks who replied to my thread and the one I've link to, below...

http://www.bladeforums.com/forums/showthread.php?t=588681&


*** QUESTION ***
One subject that was touched upon in the above thread. Would inducing a pre-HT sori be considered a viable solution? (or would it be to unpredictable and stressfull for the steel?) Does horizontal spine down quenching cure the problem or just make it less pronounced? I don't do many swords, btw. I LOVE my vertical tank for knives... one long, deep plunge breaks up that vapour jacket well.







Rick