Cutting Speed Calculator (Vc)
Free cutting speed calculator: convert spindle RPM and diameter into surface speed Vc in m/min and SFM.
Cutting speed (Vc) is how fast the tool edge moves through the material. Enter diameter and spindle speed, and this cutting speed calculator returns Vc = π × D × n / 1000 (m/min) with the SFM equivalent alongside — the number tool catalogs quote per material.
FAQ
What is cutting speed (Vc)?
The distance the cutting edge travels through material per minute, in m/min (or surface feet per minute, SFM). Manufacturers recommend speeds in Vc because it is machine-independent: the same Vc applies whether the cutter is 6 mm or 60 mm.
How do you calculate cutting speed from RPM?
Multiply the circumference by the spindle speed: Vc = (π × D × n) / 1000 m/min with D in mm. A 12 mm cutter at 18,000 rpm runs at (π × 12 × 18,000)/1000 ≈ 679 m/min. In inches: SFM = (π × D × n)/12.
What is SFM?
Surface feet per minute — the imperial cutting-speed unit. One SFM equals 0.3048 m/min, so 100 m/min ≈ 328 SFM. US catalogs quote carbide grades in SFM, European ones in m/min.
What cutting speed should I use?
CNC routing: softwood, plywood and MDF 200–350 m/min, hardwood 150–300, acrylic 100–180, aluminum 100–250. Steel in a mill runs far lower, roughly 20–60 m/min with HSS tooling. Start mid-range and adjust for tool life and finish.
What happens when cutting speed is too high?
Heat. Edges dull quickly, MDF and glue lines scorch, acrylic melts and welds shut, aluminum smears onto the edge, and steel burns carbide in minutes. Dropping Vc by 20% often multiplies tool life several times.
Cutting speed vs feed rate — what is the difference?
Cutting speed is how fast the edge moves in the cut, set by spindle rpm and diameter. Feed rate is how fast the tool travels through the workpiece, set by rpm, flute count and chip load. Both must be right; the feeds & speeds calculator combines them.