I received the purchase. 
In case I haven’t said this already, I am very interested in the results.
Well, I can confirm that the spindle itself weighs 2# 4oz. A power supply should arrive later today that I can use to power it up.
In terms of actually testing it in actual use, my 3D printer hasn’t arrived yet, so I’m not sure yet if I can mount it on my 2418 or whether that will have to wait. I should be receiving the 3D printer in about 2-3 weeks from now.
If there are other tests you can think of, though, that you’d like run in the meantime, I could maybe do some. I mean, for instance, I could check to see how loud it is, and I could maybe form a rough opinion about how good or bad its runout is. I could maybe even try loading it to see whether it maintains RPM, but I’m not exactly sure how I should do that.
Power supply arrived, and I hooked it up. It runs very quiet. The motor itself is pretty much sealed. On the positive side of that, little if any dust will ever get inside it. On (maybe) the negative side, the fan basically directs air at the back of the motor, and not really anywhere else. I’m only guessing, but keeping other parts of it cool may prove challenging if doing a lot of heavy milling. For milling PCB’s, I don’t think it will be a problem though.
I found a very similar motor being used on a printed CNC machine on thingiverse, so I think it will probably work without issue:
and
That looks great.
Epilog: I ran the motor unloaded continuously at its maximum speed and monitored its temperature using a DS18b20 temperature sensor beneath the holding bracket (so, getting the least amount of circulated air onto it). It reached an equilibrium temperature of around 31C. Also, it turns out that it actually does have pretty good air flow. So, I’m no longer worried about this spindle getting too hot.
I’m curious to know if it shows down, when not at Max speed, when running through material. Maybe you can’t test that until you get the cnc finished…
I think I’ll stick with the mainstream build, at least for the first build, so maybe much later…