Smithy CNC Mills - Manual (Page 26)

SmithyCNC Programmer’s Reference Manual: G Codes 2-11
* Axis words are programmed when G80 is active, unless
a modal group 0 G code is programmed which uses axis words.
2.17 G76: Threading Canned Cycle
Canned>
Program G76 P- Z- I- J- R- K- Q- H- to perform a
threading canned cycle. It is an error if:
* The active plane is not the ZX plane
* Other axis words, such as X- or Y-, are specified
* The R- degression value is less than 1.0.
* All the required words are not specified
* J-, K- or H- is negative
The "drive line" is a safe line outside the thread material. The "drive line" goes from
the initial location to the Z- value specified with G76. The Z extent of the
thread is the same as the drive line.
The "thread pitch", or distance per revolution, is given by the P- value.
The "thread peak" is given by the I- value, which is an offset from the drive line.
Negative I values indicate external threads, and positive I values indicate
internal threads. Generally the material has been turned to this size before the
canned cycle.
The "initial cut depth" is given by the J- value. The first threading cut will be J
beyond the "thread peak" position. J- is positive, even when I- is negative.
The "full thread depth" is given by the K- value. The final threading cut will be K
beyond the "thread peak" position. K- is positive, even when I- is negative.
The "depth degression" is given by the R- value. R1.0 selects constant depth on
successive threading passes. R2.0 selects constant area. Values between 1.0 and
2.0 select decreasing depth and increasing area. Values above 2.0 select decreasing
area.
The "compound slide angle" Q- is the angle (in degrees) describing to what extent
successive passes should be offset along the drive line. This is used to cause one
side of the tool to remove more material than the other. A positive Q value causes