Thumbscrew length and re-attach cup washer

[Asallante]

Hello, one of the plated brass thumbscrews on my Curlew was broken in half when I got it. Must have been dropped... I bought a replacement but it is about an inch shorter than the original... In order to use the built-in handle I was going to shorten the original one to match the new one. When fixing the cup washer back on (was going to just rivet it instead of fit a screw), do I need to treat the tip in any way - I read somewhere that a heat/quench cycle might be required? Anything else to be wary of? Many thanks!

[Asallante]

In the end I didn't bother with any heat treatment... perhaps I should have as the tips began to split when riveting. Both the new screw and the shortened original one. To keep tip intact and getting any worse I filled it with solder using a blow lamp. Cup washer moves freely and shouldn't come off so functions just fine - happy enough with that. Next time I might do it differently though