Any bending shoe is sized for the given conduit diameter. Attempting to bend conduits other than the diameter specified by the shoe size will result in either flattening, kinking, rippling, or similar deformation of the conduit. Damage to the bending shoe may also result. The only exception are the ½”, ¾” and 1” EMT hand benders and other benders designed for PVC Coated Rigid. When bending ½” Rigid, the ¾” EMT bender is used and so on, up to 1” Rigid where the 1 ¼” bender is used. Using a hand bender like that for anything over 1” for rigid conduit is EXTREMELY difficult, that is why we do not carry one.
When bending PVC coated Rigid the use of a bender designed to handle PVC coated should be used, and the same rule applies; bend 1” PVC Coated in a 1 ¼” shoe.
Gardner Bender FAQ 