Can Velocity
Is cutting velocity the same as RPM?
No. Cutting velocity is the linear speed of the cutting edge relative to the workpiece, while RPM is rotational speed. The control derives RPM by dividing the velocity by the cutter circumference, so the same velocity yields different RPM depending on tool diameter.
Why does tool diameter matter when setting cutting velocity?
Larger diameters generate higher surface speed at the same RPM. A spindle setting that is correct for a small end mill can be dangerously fast for a large face mill, causing overheating, chatter, or premature wear.
Why do machinists consider cutting velocity important for chip control?
Proper velocity lets the cutter form a clean chip instead of rubbing the workpiece. That improves chip evacuation, reduces heat, stabilizes edge wear, and helps maintain surface finish and dimensional accuracy.
Cutting velocity, often called surface speed, is the linear speed at which the cutting edge moves relative to the workpiece, expressed in m/min or SFM. Machinists use it to calculate spindle RPM from cutter diameter and workpiece material; it directly controls tool life, chip formation, heat generation, surface finish, and dimensional stability. The term 'Can Velocity' is not standard in CNC or millwork.
On the shop floor, cutting velocity is set before spindle RPM. The machinist selects the recommended surface speed for the work material and tool type, then the control derives RPM from cutter diameter. Feed rate is matched to keep chip load in the valid range. In a CNC mill, too low a velocity causes rubbing, built-up edge, and heat concentration; too high creates edge wear, chatter, and thermal drift. In millwork and edgebanding, incorrect surface speed shows up as tear-out, burn marks, and glue-line instability. For tolerance-critical work, velocity is a process-control variable, not just a productivity setting; it affects thermal growth, size consistency, and surface integrity. Operators listen to cut sound and watch spindle load, adjusting velocity to protect cutter and part. Even an otherwise perfect program will fail if velocity is outside the material’s working window.
Rubbing instead of cutting: When spindle speed runs too high for the feed rate, the tool wipes the material rather than shearing it, generating heat and accelerating edge wear. The resulting glossy surface still fails dimensional and finish requirements.
Burning on wood, MDF, or laminate: Excessive cutting velocity with slow feed scorches edges in millwork, leaving burn marks and melted glue lines. The real fault is surface speed and feed mismatch, not necessarily a dull cutter.
Chatter and size drift in metal: Velocity that is too aggressive for tool stickout or rigidity excites vibration, which ruins surface finish and deflects the cutter. This pushes features out of tolerance and accelerates tool breakdown.