TECHNICAL TIP #29; DRILLS; DRILLING ON INCLINED SURFACES:
Drilling on inclined or curved surfaces can generally be accomplished by a reduction in feed. After the drill tip has penetrated past the incline or curve then feed rate can return to normal. Jobber length drills will need a greater reduction in feed than stub length drills.
  Incline          Stub            Jobber
    1                0%                30%
    2                20%              40%
    3                35%              50%
    4                50%
    6                70%
Incline angles or curves more than 6 must be spot drilled or milled flat.
Drills should be always have self-centering point geometry when used on any irregular, inclined, or curved surface.

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