What is the maximum practical raise or working stroke?
Generally, standard raises are up to 12 inches on 1/4- and 1/2-ton models and 18 inches on the 2501 (one ton). Maximum raises available for the larger diameter screws are limited only by the available length of bar stock from suppliers. Practicallength will be affected by whether the screw is to be subjected to compression or tension loads. Depending on diameter, the length can be limited due to deformation of material in the machining process or column strength of the screw when subjected to compression loads. Long raise applications should be checked with Duff-Norton for the following: a) Side thrust on extended screw (see question 11) b) Column strength of screw (see question 12) c) Thermal rating of screw and nut (see question 13) We suggest guides be used on all applications. The longer the raise, the more important this becomes.
