pneumatic die grinders-- cheap v quality?

Hi!
I do marble carving; started somewhat recently. I've used chisels so far, but I really need to look at rotary for undercuts and delicate areas.
I'm considering foredoms, but, air die grinders appeal-- buy a compressor, which I need for many things anyway , and then plop $20- $100 for a pneumatic die grinder. They're also higher-rpm, possibly a benefit though overheating can be as much a worry at high rpm as chatter may be at low.
For both I worry about dust. Marble... seems harder than mild steel, when I accidentally forged some mild steel chisels they mushroomed over instantly; but is rather softer than tool steel. So the case may be made that some parts in the die grinder are going to abrade anyway so I should get cheap and recyclable grinders?
This varies categorically. I don't buy dirt-cheap bits for example, the steel quality and grinding precision is pitiful; a mid- range I find sufficient value for my needs. I do buy cheap ear protection, gloves, some lifting equipment-- sometimes the difference between name brand and brand X is only that, and the products are identical.
So where do die grinders fall? What brands do you like? If I might burn through bearings; are some better shielded for longer lifespan --enough so, that $/hour used is lower? Harbor freight? Random ebay powersellers? Another issue, beyond bearing slop, is air consumption (also a result of machining tolerance). My compressor does 8cfm, theoretically, at 90psi; but if name brand vs. brand x is a difference of a few cubic feet per minute, might be worth the name brand? If only for the noise (quiet matters) :-)
thanks!! -Bernard
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i use the harbor freight ones ,throw away when they go bad.i bought a expensive one and it only lasted a little longer..lucas
http://www.minibite.com/america/malone.htm
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Grinders won't fail if you keep them lubricated with air tool oil. Don't waste your time on fractional horse power die grinders. Purchase a one horse power die grinder for about $100
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Bernard Arnest wrote:

Pay attention to the RPM. Proper speed varies depending on the target:
Fine grinding < 10,000 RPM Rough grinding and buffing 10,000 - 20,000 RPM Metal > 20,000
They cost less than $20 at HF. If it wears out, toss it.
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