Rockwell Automation 8520-MUM 9/Series CNC Mill Operation and Programming Manual Documentation Set - Manual (Page 664)

Milling Fixed Cycles
Chapter 26
26-32
The format for the G87 back boring cycle is:
G87X__Y__Z__{I__J__K__}R__F__L__;
Q__
Where : Is :
X,Y specifies location of the hole.
Z defines the Z point level. The Z point level in this case is the top of the hole
that is being cut by the back boring operation.
Q or I,
J, K defines the tool shift amount and direction.
R defines the position beyond the hole bottom so the tool can safely shift.
F defines the cutting feedrate.
L defines the number of times the milling fixed cycle is repeated.
(See section 26.3 for a detailed description of these parameters.)
Important: This cycle requires an existing hole through which the back
boring tool can be safely lowered prior to the back boring operation.
Figure 26.14
G87: Back Boring Cycle
Spindle
orientation
Hole bottom
Z point level
Spindle orientation
Spindle orientation forward
after returning to initial
point level
Initial point
level
Cutting feed
Rapid feed
Spindle rotation forward
1
2
3
4 5
6
7
8
(G87): Back Boring Cycle