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In this article, we describe how to use G33 and G34 codes for thread cutting in CNC lathe machines with all details and examples.

G33 and G34 Codes Introduction

The following preparatory functions are available for cutting threads.

G33: Thread cutting with constant lead / tapered threads / screw threads.
G34: Thread cutting with linear lead increase / decrease

The spindle speed is read from the position coder on the spindle in real time and converted to the cutting feedrate for FPM, which is used to more the tool.

Spindle speed must remain constant from rough cutting through finish cutting, else incorrect thread lead will occur.

G33 and G34 Codes Format

G33 IP_ F_ ;
IP : End point
F : Lead of the long axis

The range for thread lead is 0.0001 mm to 500.000 mm

G34 IP_ F_ K_ ;
IP : End Point
F : Lead in longitudinal axis direction at the start point
K : Increment / Decrement of lead per spindle revolution.
Range for K is 0.0001 to 500.000 mm/rev.

Things to Know

1. Feedrate override is not effective (fixed at 100X) during thread cutting
2. If FEEDHOLD push button is pressed during thread cutting, the tool will stop after a block not specifying thread cutting is executed, similar to single block.

CNC Lathe | G33 Cycle | Tapping Example

O5555 ;
T0000 ;
G0 X0.Z-100 ;
T0303 M07 ;
G97 S200 M04 ;
G0 X0. Z5. ;
G33 Z-20. F1.75 ;
/ G01 Z-20. F1.75 ;
S0 ;
S200 M03 ;
G33 Z5. F1.75 ;
/ G01 Z5. F1.75 ;
S0 T0000 M09 ;
G0 X0.2-100. ;
M05 ;
M30 ;

Need to more?

In this article, we described How to use G33 and G34 codes for thread cutting in CNC lathe machines with all details and examples. For more details;

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