What should I be looking for in a spindle?

What should I be looking for in a spindle? I’m pretty tempted by the really cheap ebay one here: http://www.ebay.com/itm/CNC-0-3KW-ER11-12-24-48V-SPINDLE-MOTOR-For-Engraving-Machine-Carving-GRINDING-/121120129374?pt=LH_DefaultDomain_0&hash=item1c3352815e

Is that going to be enough to do any reasonable milling in wood? Soft metals? By reasonable milling I mean actually forming a shape rather than simply engraving the surface.

If that thing is absurdly sketchy and unlikely to work out for me, what would you recommend?

300W doesn’t sound like much.
Since a Dremel 4000 has 175W it would kind of work but would probably be terribly slow and not able to hold it’s RPM under any load.
For comparison:
My cheap, chinese CNC is sold either with a 900W water cooled spindle or my 2.5KW one.

Alright so that one is sure to be wildly insufficient if it takes 1/3 the power yours does, but do you have any numbers for torque on yours? Wattage seems like an awkward measure because a 700W high quality motor might end up being so efficient it has more torque than a 800W mystery chinese product.

No numbers.

I would stick with something like a Bosch Colt router. Commonly available and easy to get replacement parts if you ever need them.

What collect sizes do you get for the colt?
What’s the runout?

The Colt comes with a 1/4" collet, but you can get 3rd party collets in any size you want. I’ve never measured the runout in the spindle, all I can say is that it’s ‘adequate’ for light milling.

6.35mm… So you can mount 6mm cutters but no 8mm woodworking cutters (a standard size in manual routers)

I’m a couple days late on this thread.

I actually have that same model spindle (I have lots of spindles like this that I’ve tested, including an smaller 180w version, and a larger one at 800w).

IMO: Both the 300w and teh 180w are great for things like engraving, specfically circuit boards, but if you’re planning to cut some actual material (profiles, pockets, etc) then I would suggest looking into something else.

There is an 800w version that I also have, which comes with a VFD, and you can find in 110v (if that’s an issue) which is much better than the 300w, but even that is severely under powered compared to the colt. At full performance that 300w spindle is only .40hp, where the colt is 1 full hp and IMO gives you really close to that (it’s very difficult to bog down)

I also have the Porter Cable PC450, which is rated as 1.25HP, and has a softer start than the Colt. I also think the PC450 is a little quieter (even though it’s more powerful). I can’t vouch for it’s longevity though. I have used the colt pretty regularly on a mid-sized cnc router for about 6 months and it’s great. The PC450 is only a few weeks old, so time will tell with that one.

How big is the machine you’re building? If it’s not a monster, I’ve suggested many times that people start with a standard Dremel (or clone) while they’re getting their feet wet (and breaking bits, and stalling their routers, etc). For the price (a generic one can be had for around $15) it’s a great way to cut started.