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An old timer at the hangar told me to stop using safety wire pliers for cotter pins
Honestly I thought he was just being a grump about new tools. I've been using those little wire twister pliers for years on brake caliper cotter pins in my shop. But last month I had a pin come loose on a Cessna 172 after just 30 hours of flight time. The pliers had over-crimped the pin and created a stress fracture right at the bend. He told me to just use my fingers and lineman's pliers to seat it properly, no twisting. I tried his way on the next three jobs and honestly the pins sit way more snug now. Has anyone else had safety wire pliers mess up a cotter pin installation without realizing it?
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amy_martin1d agoMost Upvoted
That explains the cracked cotters I've been finding lately on our King Airs.
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simon_carr1d ago
Not sure this is really that serious. I mean yeah if you overtighten stuff it can crack but I've been using safety wire pliers for cotter pins for like 8 years now on my own stuff and never had one break yet. Maybe it's more about how hard you're cranking them rather than the tool itself.
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jessem5921h ago
Simon, you're running on luck more than skill there. The real issue isn't just torque, it's that safety wire pliers are made of much harder steel than your average cotter pin, so they can leave micro-cracks in the pin even with normal hand pressure. You won't see them, but over time vibration spreads those cracks. I learned this the hard way on an old Cessna where the pin just snapped in half during a preflight, and it looked totally fine until it let go.
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