Try this:
http://www.lowes.com/ProductDisplay?...llow&cId=PDIO1
I made my own without the diamond edge to get some broken screws out and ran it CCW so the screw stub backed out when I got deep enough. That worked ok - not having to make the bit seems a lot easier though.
About the 1708 - each layer of properly done 1708 is about 0.044" thick