Differential quench

[Chris Railey]

I was re-reading "The Complete Bladesmith" today and I read that if you clay a blade before HT then no tempering is needed because the spine is softer and blade hard. I have done this many times but I have always tempered the blades as normal. Has anyone ever done a differential HT and then not temper the blade. Anyone done testing on a blade With this kind of HT?

 

[EdCaffreyMS]

In the past I've done it. Using that method you can get away without tempering....but only on certain steels, and with those quenching methods/media that most would consider "sub-par" today. The question is.... should you? My answer is no.

Generally, the reason you COULD get away without tempering, is IF you did not achieve full hardening. At the time Jim wrote those books, it was very common place for Bladesmiths to use less then optimal quenchants, and very often we did not achieve the given steel's maximum hardness when quenching.

The bottom line is that no matter what the method, IF you achieve full hardening, at the very least, it's advisable to do a stress relief, or run the risk of stress cracks.

 

[Chris Railey]

Thanks for the response. I think I will stick with a favorite saying "If it ain't broke don't fix it". Since I have always tempered I will continue to do so. IF I do not reach full hardness in the edge and still temper there is no harm done. IF I do reach full hardness and do not then I MAY have trouble and that is enough reason for me to still do it. Cheap insurance.