On Mar 11, 7:46*pm, wrote:
*I've got myself into a situation -
I need to drill through 6 2X8 joists which are accessible only from
the one side. They are spaced 2 feet on centers. (need to pull cable
across to the center of the floor). The joists are sitting directly on
concrete, and the decking is 1 1/2" (you read that right) plywood.

What is the lowest power-requiring type of drill to use

Well, a drill that makes minimum sawdust uses lowest power; I'd
consider a length of black iron pipe with a tack-welded hole
saw on the end. If you support the iron pipe outboard of your
deck to be level, it should shoot straight enough to get to the
destination.

Just get a (disposable) hole saw and a 20' length of pipe, fit 'em
together and put a T handle or brace-and-bit on the drive end.
One or two supports to keep the shaft level (you can drill the
first hole with a standard setup, the shaft will rest in that hole
and you will want to level it carefully before doing the second).

After each punch-through, retract the drill and pull out the
wood plug.

It'll take a half day.