I actually own one of these 1/4″ pneumatic die grinders from Harbor Freight, and it’s not too bad. It spins at 22,000 rpm when provided a steady stream of 90 psi air, and does its job quite reasonably.
Sean and I also saw a bunch of ’em in use at a major body shop we visited a while back. Their reasoning was that while they don’t last as long as bigger-brand-name models, they do offer about a third to a half the lifespan for about 1/25th to 1/50th the price — a good deal made even better when the employees in the shop don’t always oil ’em or clean ’em well.
For a home user, they’ll last for a long, long time. I use mine only rarely, but I’ve had it for over three years now and it’s fine. And the bottom line is that you can have a die grinder for $6. How can you go wrong with that?
1/4″ Air Die Grinder [Harbor Freight]