Straightening a Pot Metal Panel

Q.Can you give me some advice on straightening the lid for my car’s console? It may be tricky because it’s made of pot metal. It was apparently bent in shipment from the shop that chrome plated it. The lid is bowed so much it now has a 1-inch gap at the front when it’s hinged down all the way. I would appreciate any thoughts you may have on how to straighten this part.
Lauran Howard
Via Email

A.I have very little experience working with pot metal, and not all pot metal is constituted the same way. A more general term for this material is “die cast,” and it generally has a high zinc content, with some percentage of lead, copper, tin, magnesium, aluminium, iron, or cadmium added to it. The number of alloying elements and the percentage of each will have an effect on the strength and flexibility of the material.

The pot metal I have worked with was not very flexible, and even light bending pressure caused it to fracture. Your console lid has bent a surprising amount, so it appears to be different from any material I have experience with.

Most metals soften when they are heated, which leads me to wonder if there is any chance that the plating shop you used may have caused the damage; perhaps by putting a lot of pressure on the lid while polishing it. I am certainly not pointing any fingers here, just raising a question. Could you see any signs of damage on the shipping container? It seems that it would take a lot of force to bend a part that size, particularly if it was inside a cardboard box.

Getting back to your question about how to straighten it, I have an idea but I have never tested it on pot metal and there is no way that I can guarantee how well it might work on your lid.

The idea is to sandwich the lid between two pieces of plywood, perhaps 1/2-inch thickness. The plywood would be cut at least 4 inches oversize, so it would overhang the edge of your lid by 2 inches on all sides. I would use drywall screws to pull the plywood tightly against the lid (the screws would go through the overlapped part of the wood, or course). For safety’s sake, cut off the tips of the screws that protrude through the plywood.

Next, you can support the wood/pot metal sandwich on two wooden 2x2s, going across the sandwich the short way. A third 2×2 can be placed on the top of the sandwich and squeezed down with a C clamp.  You can adjust the position of the two blocks below your sandwich and center the one block above it so you can apply pressure anywhere you want. By working slowly and checking your progress frequently, you may be able to get the lid straightened this way.

(Note to readers: Lauran later reported that he returned his console lid to the people who plated it, and they successfully straightened it using a technique very similar to the one I proposed. This process may not work on more brittle pot metal alloys, but both Lauran and I were happy to learn that it worked in this case.)

This pot metal console lid has distorted from its original flat shape, and bows up about an inch at the end. Pot metal is notoriously difficult to bend without fracturing, but I describe a process here that seemed to work in this situation.
