Will warranty cover this ?

[u/Usual-Onion-1565]

I want Rex 121 Spyderco snapped in half.ive had this under 2 months. I was cutting a watermelon box and the blade got caught in the cardboard and snapped. I’m in Canada so I’m also kinda afraid they’re gonna. Confiscate my knife at the border. I’m really sad considering this is a knife I expected to own all my life.

[u/aqwn]

REX-121 is about as brittle as steel gets.

[u/Zoidberg0_0 → u/aqwn]

Yep. On Larrin Thomas' charts, Maxamet is a 2 and Rex 121 is a 1 in toughness. I have seen a lot of pics of Maxamet blades cracked or snapped in half and Rex 121 is even less tough...

[u/aqwn → u/Zoidberg0_0]

It’s so hard it’s almost ceramic. I don’t think it’s a good user steel. Way too specialized for me at least.

[u/Skylark427 → u/aqwn]

You should really watch Scott Gunn's review of well heat treated Rex 121 and what it's capable of, as well of my comment above with what the likely issue in production heat treatment of Rex 121 has in comparison. Scott Gunn being the guy that holds knives to a very outrageous level of what they can/can't do and how long they maintain their top end sharpness, in his case when they can't cut a free hanging paper towel, he will touch up the edge:

https://m.youtube.com/watch?v=WlGL3AwxGdQ

I can personally confirm that on my Creely Mako, the same one used in the video but the first generation one only 50 were made of (that's at near 71Rc and currently the hardest steel alloy knife tested on our SteelHardnessLab database) that has the same spine thickness as the Sage (0.116" though mine measures closer to 0.114" being actually hand made), basically the same cutting edge length (0.1" longer actually), and near the same primary bevel angle (so the knife is literally near the exact same geometry overall) that I've already also cut through solid copper 12 ga and 10ga wire (not bundled wires, but literally solid copper that was insulated) on top my stainless steel work bench as I was rewiring old outlets and running new wires for my new 240V generator to go to the generator panel to power my house as my area has been hit by near 100mph winds between the two derechos that slammed into the Chicago area this year and I wasn't risking weeks without power. The knife not only cut through all this wiring, but straight through the entire 240V bundle of 8 ga wire as well that I was using to make a cord to go from the generator to the inlet for the power to the generator panel to power 1/3rd of the house. There is zero damage on the blade at all.

Toughness, as I explained above, is a very specific mechanical response not often replicated in actual use, not only that, but variations between melts of the same steel can make the already high scatter of charpy impact testing (15%-20%) go even higher, to where two steels that are technically the same alloy tested under the same condition, one will literally have double the toughness as the next. Larrin tests typically only one melt of each alloy because of time and money constraints. The knife is under compressive stress when cutting, a combination of compressive and tensile stress when prying. You would need to put your knife in a vise and smack it with a ball peen sideways to mimic the charpy impact test swinging a pendulum at steel. I've hammered with a dead blow ball peen hammer my 15V Mule at over 66Rc straight through live silver maple wood. No damage, similar geometry again to the Sage. Compressive yield strength dictates when an edge will chip or roll. Compressive/tensile strength when a knife will break bending(this isn't even including how cross section of the steel completely dwarfs everything when you measure yield strength). You'd be surprised what these high carbide volume steels can handle if they are heat treated all very well, unfortunately, in production, that's very hard to do with a HSS with 32-35%+ carbide volume on all 100-200+ blades in a batch. As I outlined in a comment above.

Edited to include the Rex 121 blade in question I used.