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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.
| You may be interested also: |
| “CNC Lathe | G76 Cycle | Multiple Repetitive Threading” |
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.
3. Spindle speed override is not effective in thread cutting mode.
Threads
Variable Lead
Threads with variable lead are cut with;
G34 (End point) (F) (K)
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.
Multiple Start
Multiple start threads are cut by shifting the start point of the thread for each start, by the distance equal to pitch (lead divided by number of starts).
If the lead is 4mm and number of starts are 2, and if the start point for the first start of the thread is selected as Z4, then the start point for the second start of the thread is selected as either Z2 or Z6.
G33 and G34 Codes Examples
G33 CNC Program Example – 1
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 ;
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