Calculators
Machining calculators
Twelve calculators for the hobby machinist: speeds and feeds, tap drills, thread pitch, drill sizes, metal weight, change gears, bolt circles, tapers and sine bars.
SheetCalculators
BasisResearched
Checked2026-09-24
Starting pointRPM calculator: surface speed to spindle speedTurn a cutting speed in SFM into spindle RPM for any diameter, with starting surface speeds for 17 metals and plastics, HSS or carbide.Starting pointFeed rate calculator: chip load to inches per minuteWork out milling feed rate in inches per minute from RPM, flute count and chip load, with starting chip loads by material and cutter size.StandardTap drill calculatorFind the tap drill for any inch or metric thread at any percentage of thread, with the nearest number, letter, fractional and metric drill.StandardThread pitch converter: TPI to mm and backConvert threads per inch to metric pitch and back, and see the nearest standard inch and metric threads for any pitch.StandardDrill size converterEnter any size in inches or millimeters and get the nearest number, letter, fractional and metric drill, with the difference from each.StandardMetal weight calculatorWeight of steel, stainless, aluminum, brass, copper, bronze, cast iron or titanium stock in round, square, flat, hex, plate, tube and angle shapes.StandardChange gear calculator for thread cuttingFind the change gear train for any inch or metric thread on a lathe with a 16 TPI leadscrew (7x mini lathes) or any leadscrew and gear set you enter.StandardBolt circle calculatorX and Y coordinates for every hole on a bolt circle from the hole count, circle diameter and start angle, ready for a DRO or a mill with dials.StandardTaper calculatorConvert taper dimensions into included angle, angle per side for the compound or tailstock offset, and taper per foot and per inch.StandardSine bar calculatorGauge block stack height for any angle on a 5 inch, 10 inch or 100 mm sine bar, or the angle a known stack produces.StandardCutting time calculatorEstimate how long a turning, facing, milling or drilling operation takes from length of cut, passes, speed and feed.StandardThree-wire thread measurement calculatorBest wire size, pitch diameter and measurement over wires for 60 degree inch and metric threads, for checking a thread you cut on the lathe.
