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Machine Design

More on knife safety

I must comment on your 11/02/06 column on knife safety.

Give me a break. We learn as kids that knives are sharp. As a teenager, I cut my thumb when cutting towards my hand and the knife "suddenly released." I didn't blame the manufacturer for "designing a defective product;" I blamed myself for not listening to my parents. You can bet I'll never do it again.

Common sense has gone out the window and we blame everyone else for our own mistakes. I can't believe you recommended that the manufacturers do "a proper hazard analysis, which would have identified hazards associated with the use of their products." We no longer have to learn to survive. We can be totally stupid, suffer minor injury, file an outrageous lawsuit, and retire early. That's the new American dream. That is sad!

Andrew Farkas
Sr. Tooling Engineer

A knife should pull out of its sheath with reasonable force. When that doesn't happen, a user will pull harder on the knife and sheath and simultaneously tighten their grip. This stronger grip places a hand or wrist in harm's way when the knife suddenly and unexpectedly comes out of the sheath.

Had these accidents happened while people used the knives to cut, the court would have immediately thrown out the claims. However, the courts and juries recognized that separating the knife from its sheath is an action necessary to use the knife, and that the high force needed to separate the two components was unreasonable.

As for your comment about minor injuries, no attorney would take a case that resulted in a minor injury. The damages claimed would be so low that an attorney could not justify their time. In the cases discussed in the column, the injuries included cut tendons and nerves in the hand and wrist. These are not minor injuries. Further, knife purchasers weren't the only ones seriously injured in these cases — so were people selling the knives. This was a class-action lawsuit. It is unlikely that all of these people were "stupid" as you say.

You've probably seen the note on engineering drawings "break all burrs and sharp edges." That note isn't only to keep dimensions within tolerance. It's there to protect unobservant coworkers and purchasers from unexpected hazards and potential injury.

The bottom line: Designers should do a complete job when designing a product. Building functional products at the lowest possible cost is not enough. A good designer will do that and make a product safe to manufacture, sell, use, ship, and dispose of at the end of its useful life.

is a registered professional engineer and Certified Safety Professional involved in forensic engineering since 1972. Got a question about safety? You can reach Lanny at [email protected].

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