A canned cycle is the control doing the repetitive choreography so the program does not have to. Drilling a hole is always the same dance, rapid down to just above the work, feed to depth, retract, and a canned cycle packs that whole dance into a single block: state G81 with a depth and a position, and the control performs the entire sequence. Add more positions and it repeats the dance at each one, each hole costing one short line. That compression, one line standing in for many moves, is the whole idea, and it is one of the first pieces of real machinist fluency.
What one looks like
A drilling cycle reads roughly: G81 with a retract plane (R, where the rapid stops and the feed begins), a depth (Z, how deep the hole goes), and a feed rate (F), plus the first hole’s position. The control then executes: rapid to the position, rapid down to R, feed to Z, retract. The next line is just the next hole’s X and Y, the cycle is modal, so it stays active and re-runs its stored sequence at each new position, until G80 cancels it. Twenty holes: one cycle line, twenty coordinate lines, one cancel. Spelled out without the cycle, that same work would be sixty-plus blocks of explicit rapids and feeds, which is exactly the G-code the cycle compresses away.
The common cycles share a shape
| Cycle | Operation | What makes it different |
|---|---|---|
| G81 | Straight drilling | The basic dance: down and back |
| G82 | Spot/counterbore | A dwell at the bottom for a clean face |
| G83 | Peck drilling | Pecks out to clear chips on deep holes |
| Boring cycles | Boring | Differ in how they retract to protect the finish |
| Tapping cycles | Tapping | Synchronize feed to the thread, rigid or floating |
The table’s quiet lesson is that the cycles share structure, a retract plane, a feature depth, the position, so learning G81’s anatomy teaches the shape of all of them, and the differences are each cycle’s specialty: G83’s chip-clearing pecks, G82’s dwell, the boring cycles’ careful retracts, the tapping cycles’ synchronization. The LinuxCNC reference documents the family in one place, and the lathe world has its own larger cycles, the G71 roughing family, that take the same one-line-does-many-passes idea further.
Why canned cycles matter beyond saving typing
Three benefits stack. Compression: shorter programs, less to read, less to scroll at the control. Error reduction: the repetitive moves are in the control’s tested routine, not retyped twenty times where a transcription slip hides, the decimal-and-coordinate errors that explicit repetition invites. And standardization: a cycle is the same operation everywhere it appears, so a reader recognizes the intent instantly instead of decoding a custom move sequence. Those benefits are why canned cycles are not an advanced topic but a core one, woven through almost every real program.
The two cautions worth knowing early
Dialect fine print: the common cycles and letters are broadly shared, but parameter details and behavior are per-control, so a cycle gets read against the machine’s manual before first use, the usual per-control verification. And controller coverage: some small controllers, GRBL notably, omit canned cycles entirely and rely on CAM to expand them into plain moves, so the cycle can exist in your CAM workflow without existing in the controller. Neither caution complicates the concept; both just locate where a given cycle’s authority lives.
Canned cycles reward recall more than most topics, because they appear constantly and their structure is stable: knowing G81, G83, and the cancel on sight, and the shape they all share, turns the densest part of many programs into something you read at a glance. The free 60-second rounds on the G-code practice page drill exactly that family, which makes the one-line-does-many-moves magic feel less like magic and more like fluency.
Sources
Frequently asked questions
What is a canned cycle in CNC?
A built-in routine the control expands from one block into the full sequence of moves an operation needs: G81 with a depth and position drills a hole through its whole rapid-feed-retract dance, and following positions repeat it. Canned cycles cover drilling, peck drilling, boring, and tapping in compact, standardized blocks.
How does a canned cycle save program length?
By being modal and positional: state the cycle once with its parameters, and each hole afterward needs only its coordinates while the control re-runs the stored sequence. Twenty holes become a cycle line plus twenty coordinate lines instead of sixty-plus explicit blocks.
What are the most common canned cycles?
Drilling (G81), spot/counterbore with a dwell (G82), peck drilling (G83), boring cycles, and tapping cycles. They share a structure, retract plane, depth, position, so learning one teaches the shape of the rest.
Do all controls have the same canned cycles?
The common cycles and letters are broadly shared; the parameter fine print is per-control, so read a cycle against the manual before first use. Some small controllers like GRBL omit canned cycles and rely on CAM to expand them into plain moves.