HEIDENHAIN SW 68894x-02 - Manual (Page 544)

544 Organization mode of operation
8.2
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Drilling – Safety clearances
Drilling – Machining
The parameters apply to drilling with deep-hole drilling cycle (G74).
Safety clearances
Internal safety clearance [SIBC]
Retraction distance for deep-hole drilling ("B" for G74)
Driven drills [SBC]
Safety clearance for driven tools on face and lateral surface.
Stationary drills [SBCF]
Safety clearance on face and lateral surface for tools that are
not driven.
Driven taps [SGC]
Safety clearance for driven tools on face and lateral surface.
Stationary taps [SGCF]
Safety clearance on face and lateral surface for tools that are
not driven.
Machining
Drilling depth factor [BTFC]
1st drilling depth: bt1 = BTFC * db
(db: drill diameter)
Depth reduction [BTRC]
2nd drilling depth: bt2 = bt1 – BTRC
The subsequent drilling steps are reduced accordingly.
Diameter tolerance for drill [BDT]
For selecting the desired drill (centering drills, countersinks,
stepped drill, taper reamers).
 Drilling diameter: DBmax = BDT + d (DBmax: maximum
drilling diameter)
 Tool selection: DBmax > DB > d