The threads on Fluid Systems’ HAM-LET range of hydraulic fittings are rolled. But what does this mean, and why is this a better method than cutting threads as some other manufacturers do? Rolled threads have improved physical characteristics, greater accuracy and a high degree of surface finish. They are produced with no wastage of material, which also results in cost savings. These advantages account for the increased adoption of rolled threads. The cold forging that threads receive during the rolling process strengthens them in tension, shear and fatigue. Tensile strength: the cold working of the surface increases the tensile strength of the metal, and static tensile tests have frequently recorded increases of the order of 30% in the breaking strength of the parts. Shear strength: when a thread is rolled, the fibres of the material are not severed as they are in other methods of screw thread production, but are re-formed in continuous unbroken lines following the contours of the threads. Rolled threads resist stripping because shear failures must take place across rather than with the grain. Resistance to fatigue: thread rolling increases the part’s resistance to fatigue failu...