Machining centre calculator, spindle power, taper and machine tier from your part
Enter the part envelope, material, roughing intensity and workholding, and read the spindle power and torque the job actually needs, the recommended tool taper, the real travel once the fixture is accounted for, the axis count the geometry calls for, and the class of machine, from desktop CNC to large gantry, that can do the work.
Open the machining centre calculator A free account opens this tool. The interface is in English and nothing you enter leaves your browser.How it works
Four steps from a part envelope to a machine class you can take to a supplier.
Enter the part envelope and how it will be held
Give the part length, width and height, then pick vise, fixture plate or vacuum jig for workholding. A vise adds about 140mm to the travel needed on X and Y for the jaws and clamping space, plus 80mm on Z for tool length and change clearance; a fixture plate adds 80mm and 60mm; a vacuum jig, usable only on flat parts with enough contact area, adds the least, 40mm and 50mm. A 300 by 200 by 80mm part in a vise needs a machine with at least 440 by 340 by 160mm of real travel, not 300 by 200 by 80mm.
Pick the material, the roughing intensity and the tool diameter
Choose from seven materials, engineering plastic through hardened tool steel, and how aggressively you plan to rough it: light, moderate or heavy. Power depends on the material removed per minute and how hard that material is to cut, not on the part's size on the drawing, which is why a small hardened tool steel part roughed hard can need more spindle power than a large aluminium one machined gently. Enter the typical tool diameter too: it only changes the spindle speed and torque needed for the same cutting speed, not the power itself.
Describe the geometry and the tolerance you need
Say how many distinct faces carry features, and tick whether the part has a continuous curved surface with a changing wall angle or an undercut unreachable from any single orientation. That decides whether the job needs 3 axes, 3+2 (positioned once, then cut with 3), or 5 simultaneous axes. Then set the tolerance class and the surface roughness required, so the tool can check both against what milling alone can hold.
Read the power, taper, travel, machine tier and the honest verdict
The results show the spindle power and torque needed, the recommended tool taper from BT30 up to HSK100A, the travel the machine actually needs, the machine tier from desktop CNC to large gantry with its typical weight and budget range, whether your floor and power supply are sufficient, whether a VMC or a gantry architecture fits the footprint, and a plain verdict on whether a desktop CNC can do the job at all, with the specific reason stated if it cannot.
Eight checks from one part
Enter the envelope, material and process once and read every check that decides the class of machine you actually need.
Built to catch the machine mismatch before you buy
Most mismatches between a part and a machine are not exotic. They come from measuring the part instead of the operation, or trusting one cutoff where the job actually needs four.
Travel built from the part plus the actual fixture
A machine with travel exactly equal to the part does not fit the part: the part has to sit in a vise, fixture plate or vacuum jig, and the workholding itself eats into the travel. The calculator adds a real margin for each style, about 140mm on X and Y plus 80mm on Z for a vise, less for a fixture plate or a vacuum jig, so a 300 by 200 by 80mm part actually needs a machine with roughly 440 by 340 by 160mm of travel, not the part's own dimensions.
A four-threshold desktop verdict, not one cutoff
Whether a desktop CNC can do the job is not one number. The calculator checks travel against roughly 300mm, spindle power against roughly 1.5kW, the tolerance class against the general ISO 2768-m band, and the surface roughness against about Ra 1.6 micrometres, and it separately rules out a desktop machine the moment the geometry calls for true simultaneous 5-axis motion, which no desktop router or mill actually offers. Any single threshold is enough to fail the part off a desktop machine, however comfortable the others look.
Axis count kept apart from setup convenience
Extra axes are either a geometric necessity or a convenience, and the calculator keeps the two separate. A continuous curved surface with a changing wall angle, or an undercut unreachable from any fixed orientation, genuinely needs 5 simultaneous axes. Features spread across several flat faces only need 3+2: the fifth axis positions the part before the cut, then ordinary 3-axis motion does the machining, which mainly saves refixturing rather than solving a geometry problem.
Power, torque and taper read from the same material
Spindle power comes from the volume removed per minute and the material's specific cutting energy, then feeds directly into the torque at your chosen tool diameter and the recommended spindle taper, from BT30/CAT30 for light, fast work up to BT50/CAT50 or HSK100A for heavy roughing in steel or titanium. The three numbers are computed together from one material and one roughing intensity, instead of asking you to look each one up separately.
Frequently asked questions
Why does a machine with enough travel for my part not actually fit it?
Because the part does not sit on the table by itself. It has to be held in a vise, a fixture plate or a vacuum jig, and the workholding takes up real travel that the part's own drawing never shows. The calculator adds about 140mm on X and Y plus 80mm on Z for a vise, 80mm and 60mm for a fixture plate bolted directly to the table, and 40mm and 50mm for a vacuum jig, which only works on flat parts with enough contact area. A 300 by 200 by 80mm part in a vise needs a machine with at least 440 by 340 by 160mm of travel, not 300 by 200 by 80mm.
Why can a small hardened steel part need more spindle power than a large aluminium one?
Spindle power depends on the volume of material removed per minute and how hard that specific material is to cut, not on the size printed on the drawing. Aluminium removed at a light rate needs roughly 0.30kW; hardened tool steel at around 50 HRC removed at a heavy rate, even at a similar removal volume, needs roughly 1.27kW, about four times more, because its specific cutting energy is that much higher. A small part machined aggressively in a hard material can easily out-demand a large part machined gently in a soft one.
When does a portal or gantry machine make more sense than a vertical machining centre?
On a vertical machining centre (VMC) the table and the part move together under a fixed spindle, which stays compact and cheap to automate, but the table has to grow, and accelerate, along with the travel. On a gantry, the bridge carrying the spindle moves over a table that does not grow with the travel, so the architecture stays practical at a much larger size. The calculator recommends a gantry once the required footprint on X or Y passes about 1200mm, the point where most machining centre builders' own product lines actually switch from a VMC to a gantry design.
When do I actually need a three-phase power supply instead of single-phase?
A domestic single-phase circuit at 230V and 16A delivers roughly 3.31kW, and an upgraded 230V/32A circuit around 6.62kW. Three-phase scales far more steeply: 400V/16A gives about 9.98kW, 400V/32A about 19.95kW, and an industrial 400V/63A circuit about 39.28kW. In practice, a spindle needing more than about 3 to 4kW almost always needs a three-phase connection, because the current a single-phase circuit would need at 230V quickly exceeds what a normal domestic cable can carry, and a coolant pump, a chip conveyor and lighting all draw from the same connection alongside the spindle.
Why does titanium cut slower than a harder tool steel?
Hardness is a misleading guide here. Hardened tool steel at around 50 HRC is harder than titanium Ti-6Al-4V and has a higher specific cutting energy, yet titanium is cut at a typical 45 metres per minute against about 80 for the steel, nearly half the speed despite being the less hard material on paper. The reason is thermal conductivity, not hardness: titanium conducts heat poorly, so the heat generated in cutting stays concentrated at the cutting edge instead of leaving with the chip, which wears the tool fast unless the speed is kept low and the coolant generous.
Where do the numbers in this calculator come from, and what does it not tell you?
Every figure, specific cutting energy, cutting speed, roughing removal rate, taper power class and machine tier weight and price range, comes from published industry references: Machinery's Handbook, Sandvik Coromant and Kennametal application guides, and summarised catalogue specifications from major machining centre builders, not a lab measurement of your own machine and tool. The calculator deliberately does not compute chatter or machine damping, because there is no reliable universal model for an arbitrary combination of machine, tool and part; at a borderline result, the real check is a test cut, not another number on the screen. Treat the machine tiers and euro price ranges as a starting point for a conversation with a supplier, not a binding quote.
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