Can I tie into 220 line that's runs the a/c unit out side of the house to hook up a table saw that's in my shop about 100 feet away

I wouldn't even try. Too many violations/dangers.

If saw is 220 volts, would run new line and breaker from panel box.

Chuck

Would this be temporary or permanent?

Temp would be fine, permanent would need a new line back to panelboard.

If I have to run a new line to saw 225 feet away from main breaker box what size wire and breaker ? Saw is 3 hp 220 v 18 amps or could I put small breaker box at a/c unit with 2 breaker one for a/c other for saw the ac breakerthats feeding the a/c unit is 50 amp the a/c is 26.4 min amps thanks kevin