8 Basic CNC Programming
8.4 NC Codes
104
G84
Thread tapping
G85
Boring cycle
G86
Straight drilling with spindle stop
G89
Boring with dwell
8.4.6.5.
The Programming Mode Group
Programming Mode G codes select the programming mode, absolute (G90) or incremental (G91). These
codes remain in effect until superseded by each other. The default code on program start up is G90.
When using absolute programming, all X, Y, and Z coordinates are specified relative to origin of the
current coordinate system. When using incremental programming, each motion to a new coordinate is
specified relative to the previous coordinate.
The supported Programming Mode codes are listed in this table.
Info Table: Programming Mode Group
Code
Function
G90
Absolute programming mode: All X, Y, and Z axes coordinates are specified relative to a (0,0,0) location
on the milling center.
G91
Incremental programming mode: Each motion to a new coordinate is specified relative to the previous
coordinate.
8.4.6.6.
The Preset Position Group
The Preset Position G codes move the tool to a predetermined position or affect how future motions will
be interpreted.
The supported Preset Position codes are listed in this table.
Info Table: Preset Position Group
Code
Function
Section
Page
G28
Homes the machine. Can specify a point to pass
through on the way to the home position.
8.4.6.6.1 G28 and G29: Homing
Commands
G29
Return to reference point: Moves the tool to a
coordinate specified by XYZ. Typically used after a
G28 code.
G92
Preset position: This code works like the Set Position
command under the Setup Menu. The X, Y, and Z
coordinates following a G92 code define the new
current position of the tool.
8.4.6.6.2 G92: Preset Position
G98
Rapid move to initial tool position after canned cycle
complete.
G99
Rapid move to point R (surface of material or other
reference point) after canned cycle complete.
