I have just purchased 3/16 x 2-3/4" philips head tapcons and the recommended 5/32" drill bit. I drilled the holes using hammer-drill with ease and plenty deep as recommended. Attempting to drive the tapcon it slides right in the hole, No resistance whatsoever. Feels like the hole is to big, Checking the drill bit it states 5/32 therefore - What the heck?
5/32" is just 1/32" smaller than 3/16". My guess is that, either due to a really good hammer-drill or relatively soft or brittle surface, you drilled the holes a little too big. If the location of the holes is critical (i.e., have to be where you already drilled) then get some larger screws - e.g., 1/4". If the location is not so critical then move an inch or two away and use a slightly smaller bit and/or drill a little less aggressively.
Unfortunately the position is critical and so is the screw size - Guess i'll have to get inventive– BlaneAug 22, 2019 at 16:07
2@Blane, use the next size up Tapcons and maybe use a regular drill or take it easy with the hammer drill. What type of concrete is this? Like a cinder block? Cinder block should drill relatively easily without a hammer feature.– JPhi1618Aug 22, 2019 at 16:14
The other possibility is to fill the holes and then use ordinary screws instead of Tapcons. That works great for "toothpicks filling a hole in wood to reinstall hinges on a door with longer screws" but whether that will work here or not depends a lot on the strength needed - e.g., hanging heavy stuff on a wall vs. holding something in place on the floor. Aug 22, 2019 at 16:26
Drilling into 25-30 year old poured wall concrete, Holding up cubical style desktops so not sure I would trust the toothpick method. I may have to modify my mounts to accept the larger screws– BlaneAug 22, 2019 at 16:37
Definitely not toothpicks for that! But I would use a different material anyway if patching into concrete holes - that was just a comparison to the similar problem in wood. I would try for larger screws. Aug 22, 2019 at 16:38
Vacuum dust out of hole
Mix some epoxy and inject into hole
Drive in a tight fitting wooden dowel (obviously 3/16 will fit)
Wait for cure
Just for anyone skeptical, modern epoxies have strengths in the thousands of pounds per square inch, so this should be fine so long as you aren't driving a vehicle over the joint.– TylerHDec 31, 2021 at 2:05
Yes, epoxy is the resin that holds together fiberglass boats and carbon-fiber airplane components. Without the epoxy they'd just be a pile of floppy glass mat. Dec 31, 2021 at 19:00
Drill a hole in concrete, the fill the hole with Gorilla glue or Liquid Nails then hammer in a wood dowel the use a screw and that’s it.
2This doesn't seem to provide anything substantive over the existing "use an epoxy and a wooden dowel" answer that Harper posted over 2 years ago.– TylerHDec 31, 2021 at 2:06