Who would have thought that something that appears so simple, can be so time consuming to make?
The trouble is, when silver is thin, it is actually quite soft. When you heat it, the molecules jump around and it becomes more soft. Here's the problem... you need a pin that is thin, so you can get it though your clothes easily, and it doesn't leave a great hole afterwards. Yet you need the pin to be rigid so it doesn't bend easily and distort.
The pin has to be heated, when it is soldered to the back, so pin = soft :-( To make silver hard again, you need to 'work harden' it. By hitting it with a hammer, rubbing it with a burnisher, or tumbling it in steel shot. Firstly I tumbled mine. But when I took them out of the barrel polisher they were a bit bent. I rolled them in steel plates to straighten them, but the plates were marked, and the pins didn't look so good. So today I sanded the pin to a fine point, and rubbed it with my agate burnisher, and finally I got it to the standard that made me happy.