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  for Metal Finishing since 1989
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Can nickel solder be applied as a wear surface?

2005

I've been asked if I could repair a number of military folding knives. These knives are extreme duty, tactical gear that must be reliable with one-hand operation. The most common problem is wear on the tip of the lock tab. After repeated opening and closing, the tab becomes stuck in the locked open position, thus making one-handed closing of the knife very difficult or impossible. I have repaired this previously by welding/refinishing, but this is prohibitively expensive, and will continue to wear out. Otherwise these knives are extremely well-made for their cost. (These Knives are purchased by the servicemen themselves, so cost is major factor in selection.) I'm looking for something more than a repair. I want it to be an improvement/upgrade that I can afford to offer free of charge to any serviceman who has one of these knives with this problem, and can afford to pay shipping costs.
I hope that this request for information does find someone who is willing to advise me toward a solution.
Thank You.

Halford Leroy Foster
Toolmaker - Easley, South Carolina, U.S.A.

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I think you're looking at a design/materials selection problem. It's unlikely you can affect an upgrade without spending more than the original cost. This one should be solved by the OEM.

Jeffrey Holmes, CEF
Spartanburg, South Carolina
2005

Do you plan not to charge anything but the freight cost? A re-design and reconstruction? Gee, what other kind of tools do you make besides knives? I want you to be my supplier.

Guillermo Marrufo
Monterrey, NL, Mexico
2006

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I am not acquainted with the knife, so I can only imagine what you are talking about. However, it sounds to me that you have a classic case of re-manufacturing. Is it possible to remove the offending lock tab and replace it with a more suitable component material? If so, have them manufactured in a suitable material (steel?) and then case harden or nitride them the reduce the wear on them. Alternatively you can "rebuild" them by using brush plating (also known as tampon plating). This is quite common in remanufacturing and can be very successful. I would suggest rebuilding with chromium as this is hard and lubricious, so it shouldn't wear too quickly. You may also want to consider using a composite deposit of a metal with PTFE; this is a well known and tested technique, especially with nickel/PTFE, but I am aware it has also been done with (hexavalent) chromium - I do not know about trivalent chromium, but suspect it can be done. Good luck.

Trevor Crichton
R&D practical scientist
Chesham, Bucks, UK
2006