Sorry, I meant swaged, which means two pieces of metal were pounded together. The alternative is forged.

See Sheldon Brown:

Chromed steel cranks are almost always swaged to the spider, though there are some forged ones.

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It is difficult to seat a cotter pin with a hammer, so the cotters may still be the problem. Pressing them in really is better. I use a vise, cumbersome but effective.