Backtapers & Relief Depths
Backtapers
Backtapers are a linear reduction in the tool diameter allowing for clearance and minimal friction. Standard backtaper, .0008″ – .0010″ per inch, is generally used in steel applications where the heat generated by the bearing pads (contours) does not expand and contract the hole during the drilling process. Materials that heat and cool quickly such as aluminums, cast iron, etc. require increased backtaper to prevent the hole from closing in on the gundrill during the retract mode.
Relief Depths
Relief depths are undercuts placed in specified locations to allow coolant to lubricate the bearing pads therefore cooling the tool and obtaining optimal surface finishes. The depths of the reliefs are manufacturing standards and sometimes increased depending on the application.
