Here's a small blade test knife that I wanted to destroy to see a couple of things.
1) What the texture and grain size of the edge looked like up to the quench line.
2) Since I tend to temper a slightly harder edge on my small blades, when would it crack. If it bends too much then the edge holding quality will also suffer some being soft.
3) When would my spine break.
So I destroyed this 5160 2 1/2 test blade, differentially quenched, tempered at 375F twice for 1 1/2 hours each time. That temper tends to give me a harder edge then when tempering to 400 or 425F.
This is where by spine broke at a little over 90 degrees. The quenched edge cracked around 40 degrees. No I did not break it with my fingers...just showing how it came apart!
I cracked the edge again by the recaso a second time with out totally breaking the blade to get a good idea where the edge broke.
What I liked was was how small my grain size was on the quenched edge and the demarcation from quench line to softer spine which I think you can make out in the picture. Any comments and critiques are appreciated..tippit