CNC router vs CNC mill

The spindle tells you most of it

A router spindle runs 8,000–24,000 RPM and makes its power at the top of that range. A mill spindle runs 100–5,000 RPM and makes torque at the bottom. Those are not two settings of one machine; they are two different mechanical problems.

Soft materials want speed, because a fast, shallow cut clears chips and leaves a clean edge. Hard materials want torque, because you are removing metal by force rather than by speed.

Frames are built for different loads

A router carries a light gantry over a large flat table, because sheet goods are large and the cutting forces are small. A mill carries a heavy head on a short, stiff column, because the forces are large and the parts are not.

That is why a router with a 600mm table can weigh 40kg and a mill with a 300mm table can weigh 200kg, and why the mill is the one that will take a real cut.

Which one for which job

• Sheet goods, signage, plywood, MDF, acrylic — router, every time. The area is the point.
• Aluminium plate, brackets, panels, enclosures — a rigid router does this well and fast.
• Steel, deep pockets, tight tolerances, tapped holes — mill.
• Mixed work in a small space — a rigid benchtop router with a good spindle is the more versatile single machine, as long as you accept it will not do steel.

What people get wrong

The commonest error is buying a router because the work envelope on a mill looked small, then discovering the parts are aluminium and the router flexes. The envelope you need is almost always smaller than you imagine and the rigidity you need is almost always higher.

The second commonest is buying a mill for sheet work and discovering that a 300mm table cannot hold a 1200mm panel, no matter how rigid it is.