Chat with an old timer made me rethink how I torque control cables

I was helping this retired mechanic bench test a harness last Wednesday and he told me to back off the torque wrench on those small terminal block screws. He said I was crushing the copper strands, making them brittle after a few heat cycles. I never even thought about over-tightening wires that small since I always just went by feel. Has anyone else had a connector fail later from being too tight at the install?

2 comments

2 Comments

wesley_fox9210d ago

My first year on the job I zipped down a bunch of 10ga stranded wire on some terminal blocks like I was putting lug nuts on a truck tire. Snug plus a quarter turn, right? Three months later every single one of those connections had pulled loose from the heat cycling. I pulled one out and the copper strands were actually flattened and cracked right where the screw bit into them. Felt like a real genius holding a handful of broken wires. That old timer was probably spot on, sometimes you gotta treat those little screws like they owe you money.

the_blair10d ago

Yeah that's a real thing. I've seen guys crank down on those little terminal screws like they're torquing head bolts and wonder why the wires snap off a month later. With stranded wire you really just want it snug enough that it won't shake loose, not tight enough to squash the strands flat. If you're seeing the screw head deform the copper or leave a deep dent, you've gone too far. A good rule I've found is tighten until the wire won't pull out with a light tug, then stop. Heat cycling will do the rest of the work for you.