
CNC Machinist Calculator +
Speeds, Feeds, Taper & Tap
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CNC Machinist Calculator + puts the numbers a machinist reaches for all day into one shop app that works offline, in inches or millimetres.
SPEEDS & FEEDS
Pick a material and HSS or carbide, enter tool diameter, flute count and chip load, and read spindle RPM and table feed. Save presets for the tools you run most.
TAP DRILL
Metric and Unified (UNC/UNF) threads with an adjustable thread-engagement percentage. Shows the theoretical tap-drill size and the nearest standard drill.
BOLT CIRCLE
Hole count, diameter and start angle give X/Y coordinates for a bolt-hole pattern, ready to enter at the control.
TAPER
From two diameters and a length, or from an included angle, taper per foot or a 1:N ratio: compound-rest half-angle, included angle, taper per foot, taper per inch and ratio, shown in decimal degrees and degrees-minutes-seconds.
REFERENCE
Starting-point cutting speeds by material, a drill size chart (number, letter, fraction, metric), thread pitch and minor diameters, drill point depth factors and typical surface-finish ranges.
All values are conservative starting points from published data. Verify against your tooling and machine before cutting.
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What's New in CNC Machinist Calculator +
1.3.6
September 5, 2026
Turning surface-finish calculator on the Reference tab, under the taper card. Verify: open Reference, scroll past Taper calculator to Turning surface finish. Leave mm selected. Mode Ra from feed. Enter feed 0.2 and nose 0.8 (or tap the 0.8 chip). Ra shows 1.563 µm and Rt 6.250 µm. Switch to Feed for Ra, enter target 1.6 with the same nose — max feed is 0.202 mm/rev. Caption states this is theoretical; real finish is typically 1.5–3× rougher. Feed at or above 2× nose radius blanks the numbers.
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