CNC Milling drill cycles

In order to program a drilling cycle for your program, there are a few codes that must be used in order to ensure a successful drilling cycle.

Plain drilling cycle (G81)

G81 G98 Z-20. R5. F60.
G81 G99 Z-20. R5. F60.
This is a straight forward drilling cycle. The machine will rapid down to 5mm above the job (R5.) and then begin feeding with a federate of 60 (F60.) down to the depth of 20mm (Z-20.), after it has reached the required depth, it will rapid back up to the Z-level that it was on at the beginning of the cycle (G98) or it will rapid up to the R-level (G99 and R5.)
G81 instructs the machine that a plain drilling cycle is to be used. There are other drilling and boring cycles which can be used instead of plain drilling cycles, they are for more advanced uses like deep hole drilling.

Spot drilling cycle (G82)

G82 G98 Z-3. R5. P1000 F100.
The spot drilling cycle works similarly to the plain drilling cycle, except it has an added code. The spot drill will rapid to 5mm (R5.) and then feed down to 3mm depth (Z-3.), after that it will stay there for the dwell time (P1000) and then continue in the same manner as the plain drilling cycle. Note that the P-value in the spot drilling cycle must not have a point.


Peck drilling cycles (G83 and G73)

G83 G98 Z-40. R5. Q2. F100.
These cycles are specifically used when a deep bore is required (40mm + ) and your material forms long shavings that need to be broken. The peck drilling cycle works the same as the Plain drilling cycle except that at each 2mm depth, it retracts and comes back in order to break shavings and prevent them from tangling and causing problems (Q2.). G83 retracts the drill all the way out of the bore, where as G73 only retracts the drill a little bit before it returns to drilling.

Boring cycle (G86)

G86 G98 Z-20. R5. F150.


The boring cycle is specifically for use with boring bars because it instructs the machine to stop spinning once it has reached the required depth, and retract with the spindle not spinning. This helps to prevent lines on the bore, in order to get a better finish. It works exactly the same as the plain boring cycle except for the way it retracts.


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