I assume that the spindles are made on CNC equipment and it's probably not going to be straight forward to redesign the rotor with a larger nose to accept the larger diameter ER collets and nut that would be required to go from ER 16 to ER 20 for instance.

As I said previously, the manufacturer may be prepared to make a "one off" but I would think that the cost would quite high.

Is it not a case of just ordering the CNC3040 with a larger spindle to cover a larger range of sizes? The 2.2 kw spindle can handle up to 1/2" and is man enough for most jobs including steel milling. I would have thought that this would be cheaper than getting a lower powered spindle but with a bespoke larger collet size.

Ali Kat