Constant lead Threading (G32) Interpolation Funtion

Tapered screws and scroll threads in addition to equal lead straight threads can be cut by using a G32 command.
The spindle speed is read from the position coder on the spindle in real time and converted to a cutting feedrate for feed-per minute mode, which is used to move the tool.

Example of threading

In general, threading is repeated along the same tool path in rough cutting through finish cutting for a screw. Since threading starts when the position coder mounted on the spindle outputs a one-spindle-rotation signal, threading is started at a fixed point and the tool path on the workpiece is unchanged for repeated threading. Note that the spindle speed must remain constant from rough cutting through finish cutting. If not, incorrect thread lead will occur.

LZ and LX of a tapered thread

In general, the lag of the servo system, etc. will produce somewhat incorrect leads at the starting and ending points of a thread cut. To compensate for this, a threading length somewhat longer than required should be specified.

Ranges of lead sizes that can be specified
Metric input = Least command increment 0.0001 to 500.0000 mm
Inch input = Least command increment 0.000001 to 9.999999 inch


1. Feedrate override is effective (fixed at 100%) during threading.
2. It is very dangerous to stop feeding the thread cutter without stopping the spindle.
This will suddenly increase the cutting depth. Thus, the feed hold function is
ineffective while threading. If the feed hold button is pressed during threading, the tool will stop after a block not specifying threading is executed as if the SINGLE BLOCK button were pushed. However, the feed hold lamp (SPL lamp) lights when
the FEED HOLD button on the machine control panel is pushed. Then, when the tool stops, the lamp is turned off (Single Block stop status).
3. When the FEED HOLD button is pressed again in the first block after threading mode that does not specify threading (or the button has been held down), the tool stops immediately at the block that does not specify threading.
4. When threading is executed in the single block status, the tool stops after execution of the first block not specifying threading.
5 When the mode was changed from automatic operation to manual operation during threading, the tool stops at the first block not specifying threading as when the feed hold button is pushed as mentioned in Warning 3.
However, when the mode is changed from one automatic operation mode to another, the tool stops after execution of the block not specifying threading as for the single block mode in Note 4.
6. When the previous block was a threading block, cutting will start immediately without waiting for detection of the one-spindle-rotation signal even if the present block is a threading block.
G32Z _ F_ ;
Z _; (A 1-turn signal is not detected before this block.)
G32 ; (Regarded as threading block.)
Z_ F_ ; (One turn signal is also not detected.)
7. Because the constant surface speed control is effective during scroll thread or tapered screw cutting and the spindle speed changes, the correct thread lead may not be cut. Therefore, do not use the constant surface speed control during threading. Instead, use G97.
8. A movement block preceding the threading block must not specify chamfering or corner R.
9. A threading block must not specifying chamfering or corner R.
10. The spindle speed override function is disabled during threading. The spindle speed is fixed at 100%.
11. Thread cycle retract function is ineffective to G32.


Neesa Technologies Ltd said...

It covers information that is either extremely hard to find, privileged for programmers. Thanks for sharing this information which is useful for all.

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Ghumar Dubb said...

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Makn said...

its a nice tutorail, good explanation of interpolation function.

kopiluwak nya said...
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