Patrol Machete Issue

[Andrew Lynch]

I just realized that my PM has a bit of a ripple in its edge (and behind the edge) in the sweet spot. I have been chopping hardwood, and I don't feel like the knife is performing badly given its ultra high-performance grind and edge.

However, I am curious as to whether this has happened to others. If so, did it lead to major blade failure?

I don't want this blade to die.....I've put a custom handle on it and really love it. Any suggestions on how to remedy the ripple?

 

[Cliff Stamp]

With repeated impacts the ripple will grow until the ductility is exceeded at which point the steel will rip and gross failure will set in. I have seen it on two Patrol Machetes and many other blades. The only way to completely remove the effect of the ripple would be to anneal the blade, pound the ripple out and harden it again.

What will work better than nothing is to pound it out going very light with a hammer, taking quite a long time using many little taps. Now find out where it has been tempered and do a two hour temper at 25 degrees F lower to act as a stress relief. If you don't do the stress relief the ripple will crack quite easily with subsequent impacts because it is in a highly fatigued state.

If you have not already done so, try lowering the edge angle. This will reduce the impact shock and focus rippling on the edge, not on the main blade body. It will of course make the edge more prone to damage, but this is much easier to repair than a wave in the primary grind.

The other option is to just grind it out, if it is not too deep you may not lose a significant amount of cutting ability.

-Cliff

 

[Andrew Lynch]

Thanks Cliff. I'll try hammering it straight a bit, I think. Unfortunately, it is quite deep so grinding it out is not an option.

 

[Cliff Stamp]

You should be able to tap it out, you can also just squash it straight using a vice or heavy pliers. In any case go as slow as possible. The stress relief is also pretty much mandatory (just do it in your kitchen oven), otherwise it will do the same thing even easier and this time is likely to just break completely out.

-Cliff