Don't think like that, just because its big doesnt mean it's strong. Ive sheared an m12 bolt one-handed with a 1/4" drive ratchet, and ive briefly (accidentally) put my whole weight on a single m8 bolt that was fine. Pay the extra pennies for proper, rated bolts/set screws. Those look like disc grub screw to me, which need bugger all tensile strength. If youre getting them welded in you dont need countersunk heads anyway, just grind the head off a normal bolt and weld the shaft in place.
You wont be able to thread the existing hole for your bolts anyway, as if the bolt fits through the hole now then the hole is already too big to tap for that size bolt.
EDIT: in fact pellowe will tell you all about using properly rated fixings and fittings, wont you pellowe.
You wont be able to thread the existing hole for your bolts anyway, as if the bolt fits through the hole now then the hole is already too big to tap for that size bolt.
EDIT: in fact pellowe will tell you all about using properly rated fixings and fittings, wont you pellowe.