Tips/tricks for HT on long thin blades?

[Bobby Urban]

I am working on a sushi knife and the blade with full tang handle is 14" and will be rather thin by design.  This will be my longest and thinest blade so far and I am a bit concerend about HT.  

How do you all keep them straight?  Or how do you straighten them post HT if there is a little WOW in the blade?  

thanks for any help - here is a pick of my current sushi knife(gift) and the one I am working on cut out from a damascus billet
 

[kbaknife]

What steel type?
How thin at the spine?

[Doug Campbell]

I've been forging my kitchen knives from round bar stock Bobby. I have been leaving the blades around .100" at least on the edge till after heat treating and tempering. Then finish grinding and sanding "hard". If I go thinner I start having issues with warping. I was planning to try alluminum heat sinks if that didn't work but haven't had to.

Hope that helps.

[srtben]

I straighten all my blades during the temper cycle.
Just clamp it between 2 rigid bars or angle iron, it should come out straight as an arrow! If it is warped to terribly bad you may want to temper it once before clamping it straight.

[Bobby Urban]

Unfortunately(as it regards HT) it is a slow twist of 15n20 and 1080 so there is the issue of "uglyness" if I clamp a piece of stock to the spine during HT due to etch quality.  As far as thickness at the spine it will be less than an 1/8 - leaning toward a 1/16th at the handle if I am able to get it finished correctly.  I have a long wat to go and it remains rather thick at this point 1/8" full length right now.  I will grind the edge bevel a bit more, shape, polish and go for it.  Worst case, enough steel remains for a nice hunter if it totally fails.  

Ben - are you saying two flat pieces?  Or a 3pt clamp where you have a bit of reverse stress on the effected area in hopes that the final rebound will be correct?  I like the idea of two pieces of flat stock - seems simple?

Thanks guys - I will post pics as I get it moving along.

[srtben]

Yep just 2 flat pieces, no need to over bend. It works like a charm! I just use some little 3" c clamps and as many as are needed.