Been thinking about adding a small high speed milling spindle to the side of a denford triac or emco mill 50 to create a nice little unit for making small aluminium moulds.

The alternative is to push the orignial spindle past it's comfort zone with a new vfd and and motor/pulleys, but I'm not sure how practical this would be. For small alu ballnoses sub 1mm high speed spindle are prob going to be a must. I would imagine 24,000 rpm would be ideal but the emco for example only hits about 3000 max. Will the bearings take it?

has anyone seen this done on a mini mill? Travel across the bed is going to be the limiting factor. I am going to have to get the spindle as close to the centre of the main spindle as possible.

here are a few examples

CNC Cookbook: Add-On High Speed Spindles

the larger the machine the easier this would be, rigidity I can only imagine would not be critical due to the fact the tiny ball mills are more likely to bend first before a spindle mount will?