Shoulder bolt specifications call out the shoulder diameter, shoulder length, and threaded diameter; the threaded length is fixed, based on the threaded diameter, and usually quite short. It is usually used for revolving joints in mechanisms and linkages; when used as a guide for the stripper plate in a die set its called a stripper bolt.
A lag screw is similar to a wood screw, but generally is much larger with a hexagonal head.Lag bolts are designed for securely fastening heavy timbers to one another, or to fasten wood to masonry or concrete.