G87 Back boring

Mach3 Mach4 G-code · Mill

Goes down through the hole with the spindle stopped and shifted, then cuts upward to make a back counterbore. The words differ between Mach3 and Mach4.

Format

G87 X Y Z R I J [K] [P] F

Addresses

Address	What it does
`X Y`	Hole position
`I J`	Shift to clear the hole with the spindle oriented
`K`	Mach3 top of the counterbore
`Z`	Mach3 bottom position below the part, Mach4 back bore end depth
`R`	Mach4 start point below the part
`F`	Feed rate

How it works

Modal, canned cycle group. Cancel with G80.

Example program

G0 G20 G90 G54 G17 G40 G49 G80 (SAFE START, INCH)
T8 M6 (BACK BORE BAR)
S1500 M3 (SPINDLE ON)
G0 X1.0 Y-1.0 (HOLE)
…

The full 8-line example is in the app. Example is in inch. Check offsets and clearances first.

Watch out for

Mach3 uses K for the counterbore top and Z for the low point. Mach4 starts at R below the part and cuts up to Z.
Needs spindle orient, M19. Prove I and J with the spindle off before the first part.
Mach4 always returns to the initial point. G99 is not allowed.

Related codes

G76 · M19 · G80

G87 on other controls

The same number can mean something different on another control.

Control	Meaning
Fanuc	Back boring cycle
Haas NGC	Boring cycle, stop and manual retract
Mazak (EIA)	Side drilling cycle, live tool
Okuma OSP	Back boring cycle
Mitsubishi M70 M80	Back boring cycle
Brother Speedio	Back boring cycle
Fagor 8055 8065	Rectangular pocket canned cycle
LinuxCNC Tormach	Back boring cycle, not implemented
Hurco WinMax (NC)	Back bore (ISNC) or chip breaker (BNC)
Fadal	Bore in and out, Fadal G87
Swiss (Citizen Star)	Side drilling cycle

Every G-code for Mach3 Mach4 in your pocket. The app has the full example programs, search by number or shop word, a line decoder and calculators for tapping, threading and drilling.

Open G87 in the app All Mach3 Mach4 G-codes

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