I bought a new drill when I got these bits, Porter Cable from Lowes. The drill bit was wobbly in the drill press so I brought the drill press back. came home with a new one, used the same bit as before because it was handy. it wobbled too. pulled out another piece on a whim and it pierced right through. So be careful which ones you use if you need to be precise. I got them mainly for use on my wood lathe, luckily the tailstock on the lathe keeps the bit stationary so my holes are perfectly round and not oblong.