buy a high quality grinder... they dont leave you with metal chips in your weed
I bit the bullet and dropped 110 on a hugeeee hard anodized 4 piece aluminum space case.. I've grinded like more than a few elbows with it... I grind like 2 zips in 25 minutes for making oil
still turns just as good as the day i bought it, 3 years later.
Some people call me crazy for spending that much on a grinder, but it's worth it given how much I use it and how well it works.
just sayin'
coffee grinders tend to seperate your keif from your material... farrr worse than letting it fall on a screen...
but it depends on how much you toke I guess