A few months ago, I bunged a "U Star Grinding Machime" (sic) into a larger order from Hobbyking. It only cost £3.77 at the time so I was curious to see how good such a cheap tool could be.
Well, after exhaustive testing, I've come to the conclusion that it's rubbish.
Pros: Cheap. Powered by easily available batteries. Fits nicely in the hand.
Cons: Grinders need grunt. This one is utterly devoid of this.
I guess the push in tools should give this away. There's nothing to stop them from rotating in the hidden chuck. For the sake of it, I tried to grind away a bit of plastic. The tool stalled. I tried with hardly any pressure. The tool stalled.
Basically, this would be fine powering a fan, but for work, buy a Dremel or something proper.
I suppose the tools were nearly worth the price of the whole lot. Another lesson learned.