Using Old Exercise Weights as Project Material?

[Dave Paine]

Thanks Bob! I was just now sort of figuring it might not be worth it, as I just let it sit at about 375°F in the oven for a little while then cool slowly inside it. No effect whatsoever on the hardness.

If you want to attempt to anneal (soften) the material, you need to get it above critical temperature which is when it looses magnetism. Typically this is red hot. You then need to SLOWLY cool the item, ideally putting in e.g., sand to insulate and slow cooling as much as possible.