Cracked Steel (?) Seat on Aluminum Chair

Old 10-10-21, 10:47 AM
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Cracked Steel (?) Seat on Aluminum Chair

Here's the problem:

This image shows the underside of a thin metal (probably steel) seat on an old aluminum straight-backed chair. The three yellow arrows indicate cracks in the seat. The cracks have broken through the thin (disintegrating) padding layer on top, so now they pinch whatever pants/padding weighs down on them. No doubt the cracks will continue to spread until the seat eventually fails.

The brownish-yellow dots are the thin top padding, visible through holes in the seat created by the manufacturer.

I think the metal must be too thin to weld. It is not even as thick as the cardstock at the back of a pad of note paper. I could try laying on a layer of resin and fiberglass cloth, on top and/or on bottom, but I'm afraid the metal will continue to flex under load, eventually breaking the resin and severing the cloth.

I could replace the seat with something fabricated from plywood, but I'd like to preserve the original parts of the chair if possible. Wood also wouldn't have the contoured shape of the metal seat, and it would make the lightweight chair heavier. It would require a lot more effort (and expense, no doubt, given the price of lumber these days) compared to something like fiberglass. Depending on how I made it, it might also raise the seat height, which is not desirable.

I was looking at paint-on rubber treatments. They would be more flexible than fiberglass, but wouldn't do anything to stabilize the steel seat.

I'm wondering if there's a kind of steel tape or strapping that would stay attached for years, or some other paint-on treatment that would preserve the existing seat and its contoured shape. If not, is there some material that would function at least as well as plywood? My tools are basically a drill, a hand jigsaw, and a sanding block.

Old 10-10-21, 11:04 AM
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If you don't have a MIG or TIG welder I would first lightly sand or Scotch Brite the bottom down to shiny metal so you can see the cracks clearly. Then flex the bottom to open the cracks and mark the absolute end of each crack. At the very end of the crack drill a 1/8" to 3/16" diameter hole with one edge of the hole touching the end of the crack and the rest of the hole where the crack is heading. This will help stop the crack from propagating further.

If you have a MIG or TIG welder I would weld the cracks closed. Pay special attention to the very ends of the crack to make sure you flow over the ends to stop the cracks.

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