Speeds & feeds calculator

Search by any name you know: EN8, 316, CZ121, 2205, F55, 1.4462, Inconel 625. Then pick your tool and operation. It works out spindle speed, feed, depth of cut, metal removal rate and power, derated for the size of your machine.

Material grade, BS/EN/UNS/W.Nr. number or trade name

Tool

Operation

Work diameter mm

Teeth / flutes

Width of cut ae mm

Depth of cut ap ? mm

Thread pitch mm

Pass

Aim for

Machine size derate

Max spindle speed rev/min, optional

Motor power kW, optional

How the numbers are worked out

The calculator starts from published cutting speeds for your material, turns them down for smaller machines, and works out the spindle speed and feed. Switch to Detailed for every formula.

Cutting speed (Vc) starts from a published turning range for the material and tool where one exists (sources are listed with each result). It is then multiplied by an operation factor (for example 0.6 for drilling) and the machine derate. Operation factors and derates are workshop rules of thumb and are marked est.
RPM = 1000 × Vc / (π × D).
Feed is a typical starting value for the material group: per rev for lathe work and drilling, per tooth for milling. In milling, when the width of cut is under half the cutter diameter, the feed per tooth is raised for radial chip thinning: fz × D / (2√(D·ae − ae²)).
Metal removal rate: turning Q = Vc × ap × f (cm³/min); milling Q = ae × ap × vf / 1000.
Power uses the specific cutting force kc = kc1.1 × h^−mc (Sandvik model). It is divided by 0.75 for motor and belt losses.

Worked example: 25 mm EN1A, HSS, roughing on a hobby lathe. The mid-range speed is 37.5 m/min, × 0.8 derate = 30 m/min, so n = 1000 × 30 / (π × 25) ≈ 382 rev/min.

Tough and exotic materials

Austenitic, duplex and super-duplex stainless steels and the nickel alloys work-harden. If the tool rubs instead of cutting, the surface hardens and the next cut gets worse. Keep the feed up, never dwell, use sharp positive-rake tools and flood coolant, and get under the hardened layer with each pass. For super duplex, Ni-Cr-Mo alloys, age-hardened superalloys and Ti-6Al-4V, HSS will cut only slowly. Carbide is strongly recommended and is flagged in the results. For Stellite®-type alloys, tungsten alloys and hardened steel, HSS is not offered at all.

Pipework grades (A105, LF2, A182 F-grades) are mapped to the nearest material group using the hardness limits in the specification. Trade names identify materials only; see trademarks.

Safety: these are starting points. Begin at the low end, listen to the cut and adjust. Wear eye protection, never clear swarf by hand, and take care with titanium fines (fire risk) and tungsten or beryllium-copper dust (do not breathe it).

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