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The Design and Set Up of Tooling for Rotary Draw Bending

Typical example:

2.0" O.D. x .065" wall on 4" center line

Wall factor 30 - 2 x "D" of bend


Bend Die

  • Hardened tool steel or alloy steel, heat treated and nitrided

  • Clamp insert is secured with cap screws and dowel pins

  • Drive key must be parallel to clamp insert

  • Bore should have a slip fit over centering ring or spindle

  • Note: Bend dies may have special tube grooves with captive lip or Empty Bending


Clamp Die

  • Hardened tool steel or alloy steel, heat treated and nitrided

  • Preferable length is 3 X tube O.D.

  • Tube groove is grit blasted or may be serrated if less than preferred length

  • With tube held in bend die, advance clamp die and adjust for vertical alignment

  • Adjust for parallel contact with entire length of clamp

  • Adjust for pressure


Pressure Die

  • Alloy steel and nitrided

  • Tube groove must be parallel to back of die

  • If follower type pressure die is used, length equals 180 degrees + 2 O.D.

  • If a boosted system is used, groove should be grit blasted

  • With tube clamped to bend die, advance pressure die and adjust for vertical alignment

  • Start with minimal pressure and increase as required in small increments



  • Type of mandrel and number of balls indicated by Tooling Selection Guide

  • Aluminum/Bronze, chrome, or Kro-Lon mandrels for ferrous tubing. Only chrome mandrels for non-ferrous

  • Gain best results with most mandrels when shank projects a small amount past tangent (bend and try)

  • Lube I.D. of each tube


Wiper Die

  • The Tooling Selection Guide indicates when a wiper may be required

  • Push tube over properly located mandrel and bring clamp and pressure dies up to bending position

  • Slide wiper along tube as far as possible into bend die then secure to holder

  • Unclamp pressure and clamp dies, tip of wiper should be "very close" to tangent

  • Adjust for rake and vertical alignment

  • Lube each tube and the wiper