Tensilizing Copper Wire

The “bus bars” on the battery holders are 14 AWG copper wire:

Astable - NP-BX1 base - detail
Astable – NP-BX1 base – detail

Slightly stretching the wire straightens and work-hardens it, which I’d been doing by clamping one end in the bench vise, grabbing the other in a Vise-Grip, and whacking the Vise-Grip with a hammer. The results tended to be, mmm, hit-or-miss, with the wires often acquiring a slight bend due to an errant whack.

I finally fished out the slide hammer Mary made when we took a BOCES adult-ed machine shop class many many years ago:

Slide Hammer
Slide Hammer

The snout captured the head of a sheet metal screw you’d previously driven into a dented automobile fender. For my simple purposes, jamming the wire into the snout and tightening it firmly provides a Good Enough™ grip:

Slide Hammer Snout
Slide Hammer Snout

Clamp the other end of the wire into the bench vise, pull gently on the hammer to take the slack out of the wire, and slap the weight until one end of the wire breaks.

With a bit of attention to detail, the wires come out perfectly straight and ready to become Art:

Straightened 14 AWG Copper Wires
Straightened 14 AWG Copper Wires

The wires start out at 1.60 mm diameter (14 AWG should be 1.628, but you know how this stuff goes) and break around 1.55 mm. In principle, when the diameter drops 3%, the area will decrease by 6% and the length should increase by 6%, but in reality the 150 mm length stretches by only 1 mm = 1%, not 3 mm. My measurement-fu seems weak.

Highly recommended, particularly when your Favorite Wife made the tool.

The Harbor Freight version comes with a bunch of snouts suitable for car repair and is utterly unromantic.

11 thoughts on “Tensilizing Copper Wire

  1. Consider used bicycle spokes instead of copper wire for this application. Stainless won’t solder but the older style double-butted galvanized steel will do nicely.

    1. But copper looks so good!

      My (definitely old-school) spoke stash is all double-butted stainless; it’s been a long time since galvanized spokes were a thing. Probably can’t even get ’em off junked bikes these days.

  2. I’ve always just pulled hard on the wire. There comes a moment when you feel a tiny bit of inelastic deformation (or “give”) and you know it’s straight at that point.

    1. Little bitty hookup wire, maybe, but 14 AWG just sneers at my feeble efforts. Obviously, I need more spinach.

      1. Doing the electrical hookup for the solar system is reacquainting me with Big Copper. The 1/0* stranded for the array-pumphouse run was interesting, and the #6 bare ground wire is fun to work with, assuming you have good hand tools and patience. I’m now messing with 10-3 for the generator backup and inverter-module hookup. Actually don’t need the second phase (yet), but just in case.

        I had to use a hacksaw to make a square end to fit the 1/0 in a terminal strip. Whee. OTOH, I can sell the leftovers to the metals company. I have to remember to strip the insulation; much better return price.

        (*) 100 foot run, and I didn’t want to heat the ground…

  3. Probably a useful tip for antenna building. (Thinking of copper wire Gray-Hoverman.)

    1. If I had to make more than one of those, I’d be sorely tempted to build a CNC wire bender …

  4. Calling her your FAVORITE wife allows for some less then optimal interpretations… beter watch out not to find yourself in Basement Laboratory Doghouse wing :)

    1. Conversely, should we ever be in a situation where more than one wife would be mandatory, I already know their sorting order. This would be critical, as a man of my age is subject to certain limitations …

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