How do you remove the tumbler from the cock (hammer) on a flintlock?
The tumbler's square shaft is pressed into the hole in the cock, so it cannot simply be wiggled off by hand or pried with a screwdriver. Instead, clamp the plate securely in a vise close to the tumbler, support it well, and use a soft punch (softer than the hardened tumbler) with a hammer to knock the cock free.