I decided that I would find a small (very small) mill useful in addition to my Hobbymat combined lathe and mill. The Proxxon MF70 fitted the space requirements but reading up on it there were some potential problems:
1) The collet chuck would accept a maximum size of 3.2mm
This limited the choice of cutters. It obviously is not suitable for large diameter mills, but it also means that the normal 6mm shank small mills cannot be used. There is a commercial ER11 conversion available but at a price.
2) The speed range was high, 6000-20,000rpm and the torque was low with a 100W motor.
Again this potentially limits the cutter size but the machine is simply too small for bigger cutters. There is a commercial 4-1 epicyclic conversion available giving 1500-5000 rpm but this again is not cheap and will restrict the use of very small cutters.
I received the machine and gave it a couple of trials:
The first was cutting a 2mm keyway in a 4mm dia stainless steel shaft. I fitted the Proxxon supplied 2mm end mill and set the speed to 10,000rpm. The initial cut at a depth of 0.2mm was fine. I then increased the depth to 0.4mm This worked but sounded a bit laboured. 0.3mm was also ok. The keyway was straight and a close fit on a piece of 2mm key steel.
The second trial was to mill a 2mm square key from a piece of 3mm diameter stainless steel rod. I used the 3mm end mill for this still running at 10,000rpm. The first cut was 0.1mm depth and the next two were 0.2 mm depth without problems.
Maybe the issues are not so big and running with 'Proxxon' style cutters it will be fine
Out of interest I took it apart to see how easy it would be to make an ER11 chuck fit and make a lower reduction, 2 or 3 -1, gearbox.
The spindle is 10mm diameter with a double keyway. An ER11 collet chuck with a 10mm shank is easy to find (16EUR from CTC for example). The recess bellow the motor is 32mm diameter so I would need to find a suitable ring gear to fit.