BOLT LENGTH

threaded bolt should be screwed into aluminum part at least 2x the diameter to achieve full tensile strength of bolt. i.e. 1/4-20 bolt should be at least 1/2″ deep in part.

threaded bolt should be screwed into cast iron part at least 1.5x the diameter to achieve full tensile strength of bolt. i.e. 1/4-20 bolt should be at least 3/8″ deep in part.

threaded bolt should be screwed into aluminum part at least 1x the diameter to achieve full tensile strength of bolt. i.e. 1/4-20 bolt should be at least 1/4″ deep in part.

remember that bolts always are missing 1-2 threads at end of bolt so 1/16″ to 1/8″ of length of the bolt does not count.