tallyho,
Original and clone SAA front sights were pressed and crimped in place. You can verify this by examining the front sight slot and the press or stamping marks alongside. Some makes also use silver solder.
It's difficult for the home 'smith to duplicate this fit, so soldering is the accepted repair. Both soft (lead/tin) or silver soldering is acceptable, with soft solder being easier, of course. Make sure you THOROUGHLY clean and de-blue both the from sight base and the groove before soldering. Done carefully, soft solder won't damage the barrel or sight blue.
I've seen several attempts to secure front sights using epoxy or adhesive, but it does not hold up to recoil forces tearing the sight loose.