Grinding recurves and blade temper (ruining, fixing)

[AlphalphaPB]

I recently took a dremel to my partially serrated CRKT P/K Companion to remove the serrations and give it a bit of recurve. The blade is AUS-6M, the steel that CRKT uses in many of their blades.

The grinding
Yes, I know this high speed grinding and blade temper do not mix. I used the 10,000 RPM setting, and taped the dremel to a Sharpmaker rod to make sure I got the right angle (you might notice that lately I've been experimenting with the Sharpmaker). I also clamped the Sharpmaker to my work table since it would have been horrifying if the blade/dremel/Sharpmaker slipped. The grinding went very quickly.

This is the Sharpmaker on steroids

I knew that the temper would be affected by heat, so I ground for about 5 seconds at a time along the 1.5 inches I had to grind. Then after each 5 seconds, I placed the blade in a water bath to make sure it cooled down a bit.

The sharpening
After doing all the work, I sharpened the blade on a medium Sharpmaker rod. The dremelled area was acting strangely, in that the metal was too soft to form a wire edge. I was just pushing the edge around. This must have been the result of ruining the blade temper. I could even impact the steel a bit with just a fingernail.

The fixing
My theory is that the blade temper was ruined locally where I had done the grinding. So I sharpened like a madman in those areas where the wire-edge would not form. After about a gazillion passes on my medium Sharpmaker rod, the edge seemed to be hardening a bit. After a bajillion more passes, I knew that the steel with ruined temper was mostly removed, since the edge had hardened to the point where it was indistinguishable from the original edge.

Conclusion
The net result was that I could use a high-speed grinding tool to speed up my recurve grinding without worrying about ruining the blade temper.

Here's some pics of the recurved blade:
(the flat areas of the blade were sanded with 400 grit sandpaper, that's why it's two-toned)

Picture 1
Picture 2
Picture 3
Picture 4

recently edited to change IMG tags into URL tags, to reduce my own webserver load

 

[Will'em]

Intresting

 

[Practical Use]

Next you can go the other way and add your own serations!!

 

[misque]

5 seconds worth of grinding on a 1.5" area at 10,000 RPM is a really quick way to trash a temper on a steel without a shipload of Molybdenum in it, like say ATS-34 or 154-CM. Sorry you had to find out this way Alpha. I'm glad you were able to salvage the blade though and it has a nice re-curve to it now. Sweet. I think you actually improved the look of the blade's profile and probably it's overall cutting performance too. Hmmm...maybe my P/K Companion could use that treatment too.

FWIW,
The trick is to make your grinding passes quickly and without leaning into the grind too heavily and dunk the blade after every pass if need be. It takes longer to grind this way, but, your odds of preserving the temper are better. Dipping after a couple of passes worked really well for me when I was making knives from already hardened planer blades and tempered back Nicholson Black Diamond files.

That is quite an interesting jury rig you set up too. Very clever.