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Archive for September 13th, 2015

Harbor Freight 12 Inch Bar Clamp: Handle Failure

Harbor Freight’s 12 Inch Ratcheting Bar Clamps come with a clear description:

The 12 in. ratchet bar clamp/spreader is a light duty tool that’s perfect for delicate woodwork or scale modeling.

Yeah, right. (*)

It’s an awkward, clunky, heavy steel bar with chunky plastic fittings, not at all suitable for “delicate woodwork”. In my case, I attempted to clamp a 4×4 block against a bonded pair of of 2×4 studs before drilling a pair of bolt holes, whereupon one of the clamps failed. I deployed a spare clamp (always have a backup) and completed the mission.

An autopsy showed the problem:

Harbor Freight Bar Clamp - failed handle pivot

Harbor Freight Bar Clamp – failed handle pivot

The orange handle magnifies the applied force by the (more or less) 4:1 lever arm and applies it against two hollow plastic bosses on the side plates. The one just below the handle broke free, which is exactly what you’d expect to happen.

The through hole looks like it should pass a pivot, but that’s not the case:

Harbor Freight Bar Clamp - handle detail 1

Harbor Freight Bar Clamp – handle detail 1

I drilled out the hole just slightly to fit a snippet of brass tubing:

Harbor Freight Bar Clamp - brass bushing

Harbor Freight Bar Clamp – brass bushing

If the tubing looks slightly off-center, that’s because it is. The two halves of the injection mold weren’t aligned, as you can see along the top edge of the picture, putting the hole off-center. The broken boss took most of the reaction force from the handle: a poor bad design compounded by crappy production QC.

I filled the empty spaces with epoxy, topped it off with a pair of washers, match-drilled holes in the side plates, and ran a stainless 8-32 screw through the brass tubing:

Harbor Freight Bar Clamp - reinforced pivot

Harbor Freight Bar Clamp – reinforced pivot

The end-on view shows the misaligned handle halves:

Harbor Freight Bar Clamp - repaired - edge view

Harbor Freight Bar Clamp – repaired – edge view

It’s not nearly as stylish, but the handle pivot won’t fail again. I should preemptively repair the other clamps, but …

“Harbor Freight: The Home of Single-Use Tools” once again performs as expected.

(*) That’s a rare example of a double positive statement denoting a negative opinion, by the way.

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