That is interesting, I've only ever worked with hand held routers, so I don't associate brush replacement with the revival of a dead one - usually I've had the bearings go first and you then see the limitations of modern manufacturing that keeps things like routers so affordable (the bearings have a very light press fit in their pockets and the pockets are lightly cast so they wear out in the blink of an eye once the bearing goes).
Which is all to say a CNC setup is probably one of the best uses for a router motor in terms of long term utility. Consistent loads likely equal motor longevity. Inconsistent loads from hand held routing equals bearing wear and the heavy arcing at the brushes that erode the commutator. I've been looking at spindles if I go with a CNC, but this is good info to remember and not rule out router motor options.
I have had good luck replacing brushes on drills and a chop saw however, both of which probably see consistent loads compared to routers. You are right in that brush replacement is usually a bit of a pain. There is often a little hole to be seen in the brush holder - for those that don't know that hole is for a bit of wire or a pin to be inserted to hold the brush back away from the commutator during assembly. Once assembled the wire is pulled out through the back of the case and the brush springs forward to make contact. I first noticed these holes when rebuilding an alternator for my car in college - had to do it a couple times and on the second reassembly I realized what the holes were for. Most brush holders I've seen since have them. Probably if one has a service manual (and reads it!) this stuff doesn't come as such a revelation
Which is all to say a CNC setup is probably one of the best uses for a router motor in terms of long term utility. Consistent loads likely equal motor longevity. Inconsistent loads from hand held routing equals bearing wear and the heavy arcing at the brushes that erode the commutator. I've been looking at spindles if I go with a CNC, but this is good info to remember and not rule out router motor options.
I have had good luck replacing brushes on drills and a chop saw however, both of which probably see consistent loads compared to routers. You are right in that brush replacement is usually a bit of a pain. There is often a little hole to be seen in the brush holder - for those that don't know that hole is for a bit of wire or a pin to be inserted to hold the brush back away from the commutator during assembly. Once assembled the wire is pulled out through the back of the case and the brush springs forward to make contact. I first noticed these holes when rebuilding an alternator for my car in college - had to do it a couple times and on the second reassembly I realized what the holes were for. Most brush holders I've seen since have them. Probably if one has a service manual (and reads it!) this stuff doesn't come as such a revelation