I'm trying to drive a 2 1/2" long 3/16" diameter Tapcon into a 50 year-old concrete slab/subfloor to attach a new toilet flange.
The instructions on the case of Tapcons said to drill a hole in the concrete with a 5/32" bit. Did that with a Bosch Bulldog SDS; that part was easy.
Next the instructions say to drive the screw in with a #2 Phillips head bit. So I put a new #2 bit in my Bosch 1191VSR drill and switch it into hammer drill mode. But I can only get the screw about 1/2" in and then it just stops turning, and the bit comes out of the screw head and begins to strip the screw.
I feel like there's some technique I'm missing, or else my bits are defective. But I tried two different ones, and the same thing happened each time. Or maybe it's my drill? From stationary, I can not get the screw turning. I need to back it out a bit and start again. It feels like the torque is too low at slow speeds.
What am I doing wrong?
Best Answer
Aside from not using hammer mode, as suggested in the comments, I will report that I have had HIGHLY variable results with Tapcon's in old poured concrete - I don't recall what they claim to work in, but I begin to suspect that concrete block or green (not yet fully cured) poured concrete is more their cup of tea, or perhaps "concrete made only with "soft" rocks for aggregate." Some work as they should, some stick partway in, some go all the way in and don't hold; I think it's luck of the draw on what the concrete right at that particular hole consists of. Sometimes the threads shear right off (bit of hard aggregate they can't cut into?)
You can switch to driving them with a ratchet, but you may find that the threads shear off, or the entire shaft shears.
Since this is a vertical-down hole, you might try vacuuming it out before driving the Tapcon.
I've gone back to traditional anchors. Our local aggregate tends towards hard rocks, not crushed limestone.
They work OK as big blue overpriced wood screws ;^) which will let me use up the boxes.