Screw Thread Production

 Thread Rolling Process

Cold Forming of threads is displacing and does not waste material 

A cylindrical blank having an outside diameter between the major and minor diameters of the finished thread is rotated between hardened steel dies bearing the reverse thread form.

 The die threads penetrate the blank surface to form the thread roots and displace material radially outward to form the crests. Metal is neither removed nor wasted but displaced.

Improved Tensile Strength, Shear & Fatigue Resistance 

The Thread grain structure is not severed; instead, it is re-formed in continuous unbroken lines following the thread contours. Rolled threads have increased resistance to stripping because such failures are compelled to take place across, rather than with, the grain flow.

Threads are produced with burnished roots and flanks, free from surface imperfections that might prove to be starting points for fatigue failure. Surface layers of the thread, particularly those in the roots are stressed in compression. These compressive stresses must be overcome before the tensile stresses that cause fatigue failure can be built up. 

VERY SHORT   TWO DIE THREAD ROLLING VIDEO       VERY SHORT  FLAT-DIE THREAD ROLLING VIDEO