collets
Not sure what you are using, but collets for a PC are only about 8 bucks and you can keep your common bits in them and change out the whole collet and nut each time.
If you are using something else of course that would get expensive.
I use a bit of medium blue Loctite between the bit and the collet which dries and keeps the bit from slipping.
These work well for 1/8 shank bits with a bit of Loctite. I like the 1/2 by 1/8.
http://www.mlcswoodworking.com/shops..._bearings.html
The decimal point seems to be the most important on the z axis... x & y not so much....
ShopBot... Where even the scraps and things you mess up and throw away are cool....