DEFA – The chamfering tool for high dimensional accuracy

Precision chamfering of tough materials, front and back in One Operation

The double bladed DEFA chamfering tool creates predefined front and back chamfers in a single operation without stopping or reversing the spindle. The chamfer diameter can be adjusted on the tool. The DEFA tool is essentially used for interrupted bore edges and/or in hard-to-machine materials especially when a large burr is involved.


  • Front and back or only back chamfering of bores in hard-to-machine or highly burr-forming materials in one single pass. 
  • Dual cutting system for machining bores with longitudinal grooves, cross-bores and open bores with discontinuous cut. 
  • Chamfering diameter can be continuously adjusted directly on the tool, depending on the bore dimension. 
  • Exchangeable carbide blades with material-specific coating. 
  • No injury of the bore surface or of the thread during penetration.


Chamfering is carried out from the same side as previous boring. The two DEFA blades can be retracted radially into the blade housing. Inside the blade housing, they are held by a control system allowing them to deflect. At the same time, the DEFA blades are rigidly interconnected through the control system. First, the DEFA blades completely remove the burr. Then they meet the work piece surface and retract automatically and synchronously back into the blade housing while the chamfer is being cut. When the blades are retracted, the DEFA tool moves into the bore with the spindle rotating. The control system reduces the cutting force to a minimum. This rules out any damage to the bore surface or a thread. When moving out of the bore, the blades return to their home position and are interlocked. The back bore edge is now deburred and chamfered by backward feed.


  1. Control system 
  2. Shank 
  3. Blade housing 
  4. Blade control 
  5. Blade

Product range

The DEFA assortment is comprises of 3 tool series. Within these series, various diameter graduations are available which cover a small bore diameter range. For details on the assortment, please see the catalog.

Tool seriesBoreChamfer size
DEFA 4 – 6 Ø4.0 – Ø6.6 mm 0.1 – 0.6 mm
DEFA 6 – 10 Ø6.0 – Ø10.1 mm 0.1 – 0.85 mm
DEFA 9 – 24 Ø9.0 – Ø23.9 mm 0.1 – 2.0 mm

DEFA Product documentation

60 Years Heule