Softening 80crv2 Nakago

[AidenCC]

I've been working on a tanto made from 80crv2 (I plan to use 1080/1095 in the future) and have gotten already carved the tsuka and made the habaki and fuchi, so I did the final polish on the blade. Earlier, when I tried to sign the tang with a chisel, it would barely make a mark and dulled the chisel. I had a little more luck with a center punch, but it had to be resharpened along the way. At the time I thought it was just the difference between a high carbon steel and the mid steel I had practiced signing on, but when I went to drill the nakago ana, the cut about 1/16 of an inch in then wouldn't go any further (even with the drill press on the slowest speed, using a slow feed and with a cutting lubricant). Now my thought is that some of the clay covering the nakago chipped off enough for it to at least partially harden, and now I plan to do something to soften it. My idea is to submerge the blade in a bottle of baking soda solution and heat the nakago with a torch. I have a few questions though: has anyone done something similar and found that it doesn't hurt the finish/heat treat of the submerged blade? Will tempering it to a high temperature get rid of any work hardening from the drilling? Can steels like 80crv2 air harden with thin cross sections like this? Thank you for your time.