System information

SECTION FOUR - PREPARATORY FUNCTIONS (G CODES)
N1 G20 G90 (Inch, Absolute)
N2 G0 X0 Y0 (Rapid position to X center, Y center
for internal)(use a G65 for external)
N3 F100 (Feedrate)
N4 P121 = 0 (Angle of taper specified by the half angle or angle with the
centerline, 0 for a straight thread)
N5 P122 = 10 (Threads per unit)
N6 P123 = 1 (1 for internal threads, 2 for external threads)
N7 P125 = .03 (Diameter increment/decrement, zero for a single pass)
N8 P126 = 2 (Final Diameter for multiple passes)**
N9 P127 = 0 (X center)
N10 P128 = 0 (Y center)
N11 P150 = 1.91 (Diameter for a straight thread, start diameter for tapered
thread and multiple passes)
N12 G39 G42 G2 Z-1 V0 R.1
*1 *2 *3 *4 *5 *6
*1 Executes thread milling cycle
*
Cutter compensation (G40, G41, G42)
G41 Left Compensation
*2 Cutter compensation [Off(G40), Left(G41), Right(G42)]***
*3 Thread direction (G2 right, G3 left)***
*4 Final Z depth (P141)
*5 1
st
Z depth [(P144, If no V is specified, the control calculates the 1
st
depth
to be P140 (the clearance plane) minus P143 (the Z increment)]
*6 Clearance plane (P140)
**For multiple passes on internal threads, the final diameter must be larger than the start
diameter. Conversely, for multiple passes on external threads the final diameter must be smaller
than the start diameter.
**The correct combinations of cut direction and cutter compensation are:
G42 G2 for internal right threads.
G41 G3 for internal left threads.
G41 G2 for external right threads.
G42 G3 for external left threads.
G40 Compensation Off
G42 Right Compensation
This section will explain how the cutter compensation works and give suggestions on how to use
it optimally.
Cutter compensation is the displacement of the tool path – perpendicular to the programmed path
– by the amount equal to the cutter radius. The programmed path can be figured by the
programmer for a zero tool radius. If the parts program is written for a zero tool radius, i.e.
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