CNC Lathe | G85 Cycle | Front Boring

In this article, we describe how to use G85 cycle for front boring in CNC lathe (turning) machines with all details and examples.

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G85 Cycle Introduction

G85 cycle is used in CNC turning machines for boring holes from the front to the workpiece. It is the same as the G89 cycle as a command format, the only difference is that it is used for boring holes in the Z axis direction, not in the X axis direction.

After the command is used, boring to the other coordinates is continued by positioning the X axis or C axis. The G85 cycle continues to run until the G80 command arrives.

G85 Cycle Format

G85 Z(W)_ R_ P_ F_ K_ M_ ;

Parameters

Z_ or W_ : Final drilling depth (Z for absolute, W for incremental)
R_ : The distance from the initial level to point R level
P_ : Dwell time at the bottom of a hole
F_ : Cutting feedrate
K_ : Number of repeats (When it is needed.)
M_ : M code for C-axis clamp (when it is needed.)

After positioning, rapid traverse is performed to point R. Drilling is performed from point R to point Z. After the tool reaches point Z, it returns to point R at a feedrate twice the cutting feedrate.

You may be interested also:
“CNC Lathe | G84 Cycle | Front Tapping”

G85 Cycle Examples

G85 CNC Program Example – 1

O1234; Program number
M51 ; Setting C-axis index mode ON
M3 S2000 ; Rotating the drill
G00 X50.0 C0.0 ; Positioning the drill along the X- and C-axes
G85 Z-40.0 R-5.0 P500 F5.0 M31 ; Drilling hole 1
C90.0 M31 ; Drilling hole 2
C180.0 M31 ; Drilling hole 3
C270.0 M31 ; Drilling hole 4
G80 M05 ; Canceling the drilling cycle and stopping drill rotation
M50 ; Setting C-axis index mode off
M30; Program end
Note:
M31 : C axis Clamp


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