to grind pre-HT or not to grind... sword length blade, want hamon, don't want warp

[crimsonfalcon07]

So, I've got some 3V and some 1075 coming from Aldo, both destined for use in swords. The 3V will be heat treated by Peters, and I'm pretty confident in Brad's abilities to straighten blades. The other will likely go to Tru Grit, and I'm less sure about their abilities to straighten. I don't have the ability to straighten a really long blade myself, so I basically need for it to come back straight from HT. I'd given some thought to just not grinding it before heat treat and doing the bevels post HT. But, I find myself facing a bit of a dilemma...

Aldo's 1075 seems to take some really pretty hamons, and I know I can get it differentially heat treated at Tru Grit, and thus may be able to get a nice hamon going. However, if I don't grind until post HT, does that mean that will be a total waste? I'm thinking it should still work, from my limited metallurgical understanding, BUT... that understanding is, as I mentioned, very limited. Should I grind pre-HT and hope it comes out straight? When dealing with a blade that's 3 feet long or longer, I'm definitely worried about warp. I think I can get my grinds pretty darn good, but even a little slip up and I've got a bow, and if it comes back warped from HT, I cannot fix it in my kitchen oven, ya know?

Any advice from the masters? Last time I made an oil hardening sword, it came back warped, and I had deliberately left the edge pretty thick, hoping that would help. It didn't. So I feel like I need to grind post HT to be sure of it, or else hope that the HT company is capable of straightening it for me. Right now, I'm leaning towards doing a really shallow grind pre-HT so I can have a bit more of a guide for setting my plunge lines, but otherwise leaving most of the grinding for post HT. Thanks for any advice you may be able to give.

 

[Stacy E. Apelt - Bladesmith]

Warp to some degree in a sword is virtually a guarantee. It should be straightened right out of the quench...which is usually pretty easily done to eliminate 95% of the warping. If needed, later on small warps can be straightened at 400F. I can't imagine any professional HTer sending back a sword with a major warp in it?
You can't really avoid warp in a 24-36" piece of tapered steel. Even if you just profiled the bar, it would probably warp some. Even bevels, clean tapers, smooth surfaces, good HT with normalizing, etc. ....all will help reduce warp, but can't really eliminate it.

Everyone I know just takes the sword out of the quench, wipes it off, sights it up and down from both ends, and hand straightens with heavy gloves on. A notched board in the vise can help, too.


Grinding a blade with a hamon post HT is also not a good idea....if you want any hamon left.

The 1075 will do fine for a hamon, the 3V won't.

Gring and sand all bevels to 400 grit. Leave the edge about .030-.040", depending on how thin the sword is. After HT and clean-up, sand the bevels to develop the hamon. The edge should end up a lot thinner after all the sanding. When the blade bevels and hamon are done, sharpen to take care of the flat edge remaining.

 

[crimsonfalcon07]

Thanks Stacy. Just what I needed to know. I'm not worried about the 3V, and my understanding is that there's no point to a differential temper for that steel anyways. Mainly want to make sure that the 1075 will work appropriately. Thanks!