Thread manufacturing process

SPANENDE UND SPANLOSE GEWINDEFERTIGUNG

CHIPPING AND CHIPLESS EXTERNAL THREAD PRODUCTION

In the manufacture of threads, a distinction is made between chipless thread rolling and the mechanical cutting process of thread cutting.

CHIPPING

  • Thread cutting
  • Thread turning
  • Thread milling
  • Thread whirling
  • Thread grinding

 

CHIPLESS

  • thread rolling
  • thread forming

Cut threads acquire their shape by cutting the material, whereby the original grain structure of the workpiece is not changed, but grain structure is interrupted by the cutting process. In thread rolling, the workpiece is permanently plastically deformed by cold forming. In this process, the grain structure of the work hardened material is not interrupted. The prerequisite for thread rolling is a material that is suitable for cold forming, i.e. with a minimum elongation at break percent of 5 %.


Spanende und spanlose Gewindefertigung im Vergleich

Gewindeschneiden

Materials

  • it is possible to cut materials that cannot be cold-formed, such as grey cast iron, malleable cast iron and gunmetal

Gewinderollen

Materials

  • all cold formable materials can be rolled
  • there are no problems associated with long-chippingmaterials
  • the elongation percent of the material must be taken into account

Download list of rollable materials

Strength

  • reduced strength because the grain structure of the material is interrupted
  • notch effect in the thread base

Strength

  • higher due to work hardening of the material
  • the grain structure of the material is not destroyed, resulting in a significantly higher static and dynamic strength

Surface quality of the thread flank

  • highly dependent on the material and cutting conditions
  • higher tendency to corrosion

Surface quality of the thread flank

  • very high, press polished
  • very low corrosion tendency

Production time

  • cutting speed: 3 to 40 m/min
  • thread profile depth must be produced in several steps

Production time

  • rolling speed: 30 to 100 m/min
  • thread is produced in only one operation
  • very short processing times

Preparation of the die blank

  • precise pre-machining is not necessary

Preparation of the die blank

  • initial diameter must be pre-machined within close tolerances
  • pre-machining diameter corresponds to the pitch diameter
  • a chamfer with an angle of 10 to 30° is required

Reworking

  • a machined thread can be recut at any time

Reworking

  • reworking is problematic due to the material hardness of rolled threads

Tool costs

  • low, because the chasers can be reground

Tool costs

  • high profitability for large series production due to very long tool life

Workpiece geometry

  • thin-walled unstable workpieces (tubes) can also be cut

Workpiece geometry

  • when rolling threads of thin-walled pipes, a supporting mandral may be required
  • the ratio of inner diameter to thread minor diameter should be less than 0.67