![]() ![]() The coarser the sand gets the larger the hole ends up being, so drilling a precise diameter hole in masonry is tricky. Thus the size of the sand particles in the masonry adds a variable that isn’t present in wood or metal: if you drill in masonry made with very fine sand you get a hole nearly the exact same diameter as the drill. It’s always a little larger because instead of cutting material like a wood or metal drill does a masonry drill abrades it away. I don’t know this for a fact but my guess as to why this happens is because when you drill masonry you don’t always get a hole that’s the precise diameter of the drill. I don’t remember the exact name they give to them but when I’ve bought them at Lowe’s they’re sitting right beside their normal masonry bits and they’re approximately the same price as well. Yes, Bosch makes bits for Tapcons specfically. But then, you’d have to designate one bit specifically for cleaning, because you want it to stay at the right diameter. I wonder if drilling the holes reduced the diameter of the carbide tips a bit, so each hole was narrower than the last. One for the actual drilling and another fresh bit to clean out the hole.” That’s an interesting idea!. “Use the hex head not the screw head if possible.” Really? I used hex heads every time, but the screw heads I’ve seen take Torx bits, so they should work okay, right? I was considering renting a burlier impact driver or wrench. If the screw wasn’t going to go in with an impact driver, it certainly wouldn’t go in with a drill/driver. (And the hammer function should be off, they say, so I don’t know why you couldn’t use an ordinary drill/driver.) But that wouldn’t have let me drive home that screw that bound up. “Moreover you shouldn’t be driving them with an impact driver, the instructions say to drive them with a hammer drill.” Aha, that’s true. “Any Tapcon below 3/16” is garbage"? Do you mean 3/8" or maybe 5/16"? I don’t think they come any smaller than 3/16". Why did I bother with Tapcons? What did I do wrong? ![]() They required a 1/4" bit (so that was a third carbide bit to purchase) but my M12 Fuel hammer drill again had no problem drilling a 3" hole (I was generous.) I tapped the anchors in with a hammer, tightened them up, and done. I ended up using the smallest Parawedge anchors (with the cone-shaped nut that expands a brass collar in the hole). The screws have to be short enough that your tools can snug them down, but long enough to handle the pull-out forces, and who knows what those are? and even if you get it right, your typical DIY level tools might not cut it. ![]() So I think Tapcons are very picky about depth and diameter. Incidentaly, my M12 Fuel hammer drill had no problem drilling the holes.Īnd lo, my M12 impact driver (not a Fuel) wouldn’t drive the screws all the way in. I figured the fatter screws would resist breaking better, and the shorter screws would reduce the torque on them (because the resistance increases the farther you drive them.) Again, I used a Tapcon drill bit for the holes, but 3/16" this time. So I tried again, with 1/4" x 1 1/2" Tapcon screws. So the hole is now useless, and I have to reposition the base. Well one screw broke off in the hole about halfway down. ![]() So I bought an expensive, weird 5/32" bit, the one Tapcon recommends. The first time I used 3/16" by 2 1/2" Tapcons, reasoning that the pullout loads wouldn’t be big, and a narrower hole would be faster to drill. I was trying to attach a base for a Little Library to concrete (on a 4x4 post, into a plastic post base). The second time was today, and last week. The bit is sized specifically to let the screws drive into concrete. I chatted with the Tapcon helpline, and it turns out the screws had probably bound up in the steel base plate. I drilled holes with the Tapcon bit through the rail’s base plate into the concrete, and tried to drive the Tapcons, but they stalled out about halfway through. The first time was to attach an outdoor guard rail to the sidewalk concrete. I was kind of excited about Tapcons, because they let you a smaller hole than with anchors. ![]()
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