If it's slipping and the post it the right size it's not tight enough but be very careful as you can trash the fame by tightening too much.

torque is easy to estimate within 10-20% though
-Look up the recommended torque.
-convert to inch*lbs
-divide by the length of your wrench
-find something that weighs that much
-pick it up with three fingers.
-put the same amount of force it took to hold the item on the end of the wrench.