when i took the front caliper off ,i noticed the bottom bolt was really loose now i know why it was stripped from the guy b4 .they had thread tape on it , and i can see they drilled a hole at the end to put a cotter key in it will this work or not? the cotter key is so it can't come out.the top one is fine.

 

Not really. The caliper slides on that bolt, or at least its supposed to, and the cotter pin would continually end up further away from the caliper as the pads wear so the bolt would be able to move around a lot more as the pads wore down. It cant really fall out but its just going to get worse and could cause the bolt to break eventually. Not a good thing. I'd look at a helicoil for the spindle, or replace the spindle.