CNC Speeds & Feeds Calculator

Work out speeds and feeds for milling without digging through handbooks. Choose the workpiece material and whether the cutter is HSS or carbide, and the calculator returns spindle RPM and feed rate in in/min or mm/min. The same app also handles tap drill sizes, bolt circle coordinates, taper angles, turning surface finish and a set of shop reference charts.

SPEEDS AND FEEDS
• 8 materials: aluminum, brass, mild steel, alloy steel, stainless 304, cast iron, titanium and plastic
• Cutter type: HSS or carbide, with the base cutting speed in SFM or m/min
• Inputs: tool diameter, number of flutes and chip load per tooth
• Output: spindle RPM plus feed rate in in/min or mm/min
• Empty inputs fall back to a 10 mm (0.375 in) tool, 4 flutes and a suggested chip load that sits at or below a published carbide end-mill slotting chart. Any value you type overrides the fallback
• An end-mill diagram displays the flute count and chip load for the current setup
• Keep up to 50 named presets and recall a full setup with one tap

TAP DRILL SIZES
• 20 metric sizes and 33 UNC/UNF sizes
• Pick a thread percentage from 50% to 85% in 5% steps
• See the calculated drill diameter and the nearest standard drill

BOLT CIRCLE
• Enter the number of holes, circle diameter, start angle and center X/Y
• Read the X/Y coordinates of every hole next to a diagram
• Copy a single row or the whole list

TAPER
• Start from two diameters and a length, or from an included angle, taper per foot or a 1:N ratio
• Results: half-angle, included angle, TPF, TPI and the angle in degrees-minutes-seconds

TURNING SURFACE FINISH
• Theoretical Ra and Rt from feed per revolution and tool nose radius
• Reverse mode gives the maximum feed for a target Ra

REFERENCE CHARTS
• HSS and carbide cutting speeds for each material
• Searchable list of 243 drill sizes: number, letter, fractional and metric
• Thread pitch and minor diameter
• Drill point depth
• Typical Ra ranges

Flip between inch and mm at any time. The calculators and reference charts work without a connection.

WHO IT HELPS
• CNC mill operators checking a new tool before the first cut
• Lathe hands setting up a taper or a finishing pass
• Shop students learning how RPM, feed rate and chip load relate
• Hobby CNC router and benchtop mill owners cutting aluminum or plastic
• Anyone drilling and tapping holes in metric or UNC/UNF threads

LIMITS
• The app does not allow for machine rigidity, tool stick-out, workholding or coolant
• No chip-thinning correction is applied for partial radial engagement

Every figure is a conservative starting point taken from published data, not a guarantee. Verify it against your tooling, machine and setup, start slow and increase from there.

Recent changes:
Speeds & Feeds now opens with a result: blank fields use a 10 mm (0.375 in) tool, 4 flutes and a suggested chip load at or below a published carbide end-mill slotting chart; your own values replace them. New end-mill diagram, larger results, and full Czech, Danish, Finnish, Hebrew and Dutch.