"HotRod" wrote in message
...
the slabs are 4" think. What works better a hammer drill and masonary bit
or
a diamond dry bit in a regular drill?

Dry Diamond with a regular drill will work better than the hammer drill with
a carbide bit. The diamond won't "blow out" the back of the slab when you
exit the slab. The hammer drill will "blow out" the last bit of concrete and
make a larger exit hole. Dry Diamond blade for your circular saw will cut
through the slab with no problem. If you want to make it easier on the saw,
just cut one inch depths with every pass till you are all the way through.