I need to drill 4 40mm deep 5M holes down into a concrete garage floor (circa 1964). The holes are to receive self tapping concrete screws for a motor mount. I am not restricted to 5m holes although I would then have to get some alternative anchor screws.
Yesterdays effort with an 800W B&D hammer drill and masonry bits resulted in one 10mm deep hole and two ruined drill bits, one of which was previously unused. I have drilled plenty of holes in brick and a few in concrete in the past and never encountered this sort of problem. At this rate I am going to wear out 32 drill bits. Does anyone have any suggestions?
Yesterdays effort with an 800W B&D hammer drill and masonry bits resulted in one 10mm deep hole and two ruined drill bits, one of which was previously unused. I have drilled plenty of holes in brick and a few in concrete in the past and never encountered this sort of problem. At this rate I am going to wear out 32 drill bits. Does anyone have any suggestions?
