"Wearing in" a lockback with super steels

C

Carboniferous

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I recently picked up a Spyderco Ladybug in K390 and unfortunately there is a small bit of corrosion/surface defect on the tang of the blade which causes a small amount of grind right as the blade begins to open. I think the typical wisdom is to let the interface wear smooth through several hundred open-close cycles, but I'm wondering if that works in practice when there is such a disparity in hardness between the backspring and the tang when the defect is on the harder steel. I don't know the precise mechanics of "wearing in," wondering if anyone has spent more time with a similar issue with very hard steels who can attest as to whether I should expect much improvement.
 
Tangs on folding knives' blades are usually deliberately annealed, i.e., reheated after heat treat so as not to be as hard as the cutting steel foward of the tang. If the tangs were much harder than the spring, as with the cutting edge steel, there'd be issues of excessive wear between the tang and the backspring or lockbar.

If you can see and (hopefully) access the spot that's irregular on the tang, you might be able to lightly burnish it. Just a tiny bit of polish in that spot might make the difference. I keep old 'popsicle sticks' on hand for such use at times - the ends can be whittled to a point and used with a tiny bit of metal polish rubbed into the wood, for rubbing against spots in tight places on knives. Don't want to use an excess of metal polish that might come off the wood and be deposited in the pivot - that could cause other issues later on.

It's also possible the pivot will wear in with time and use. In the meantime, just watch for an excess of black swarf accumulating in the pivot area. If you see that, it could indicate there is excessive wear between the tang and the lockbar. If it still concerns you after some time, it may be worth sending it back to Spyderco to let them fix it and protect your warranty at the same time. And keep it lubricated, especially.
 
Last edited:
Obsessed with Edges said:
Tangs on folding knives' blades are usually deliberately annealed, i.e., reheated after heat treat so as not to be as hard as the cutting steel foward of the tang. If the tangs were much harder than the spring, as with the cutting edge steel, there'd be issues of excessive wear between the tang and the backspring or lockbar.

If you can see and (hopefully) access the spot that's irregular on the tang, you might be able to lightly burnish it. Just a tiny bit of polish in that spot might make the difference. I keep old 'popsicle sticks' on hand for such use at times - the ends can be whittled to a point and used with a tiny bit of metal polish rubbed into the wood, for rubbing against spots in tight places on knives. Don't want to use an excess of metal polish that might come off the wood and be deposited in the pivot - that could cause other issues later on.

It's also possible the pivot will wear in with time and use. In the meantime, just watch for an excess of black swarf accumulating in the pivot area. If you see that, it could indicate there is excessive wear between the tang and the lockbar. If it still concerns you after some time, it may be worth sending it back to Spyderco to let them fix it and protect your warranty at the same time. And keep it lubricated, especially.
Click to expand...
Sure, matching the hardness makes sense. I don't know what the spring is made of, I was assuming K390 would be more wear resistant either way, seems like an interesting problem.

Maybe I'll whittle a little bit of wood or get some cardboard and try to polish it down but I'd hate to make it worse. For now I think I'll just see how it goes smoothing out naturally and see what Spyderco customer service thinks.
 
Personally, I would di-ass that knife and inspect to see specifically what is going on. Knife in photos below had similar condition to OP. Galling of blade tang and lock-bar interface had started. Light stoning fixed problem before it became a more significant issue. Appling "grease" would create a condition where any metal swarth or debris will become stuck in area of problem potentially exacerbating the problem.

Photo illustrates galling that had started at the tang / lock-bar interface:
Tang-1-720Wide.jpg


Tang-2-720Wide.jpg

This knife also had a few other issued that needed addressing that could only be witnessed upon disassembly inspection:
Tang-3-720Wide.jpg
 
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