Is that a totally daft idea
I'm afraid you have some serious competition on daft milling ideas in here
Drilling machines tend to lack longitudinal stiffness support, but if you're gentle… well maybe
For myself, serious attempt one was not too bad but a decent envelope is a major problem, quite frustrating really
The other issue is the centreline on the slide moves as you move the cross slide across the tool, so the loading changes across the face of the milling slide, introducing more potential errors. A decent milling side was up to 100 quid plus last time I looked so I've gone for one of these for two hundred quid delivered

I only just got it a couple of days ago and it will take a while to sort out then test out
If I fails I've still got a fabby drilling and co-ordinates table
Getting a decent alternative to a proper mill has been an eternal problem for ME people
A proper unit is usually 500 to 3000 quid and weighs up to 3 tons, plus you have transport and space-for-it issues to contend with
So don't worry about looking daft and give it a go while they're all looking in my direction