I’ve got a hammer drill (Milwaukee) and have been using it to pilot (3/16″ X 4 1/2″) holes for some 1/4″ X 2 3/4″ cement anchors I’m using to attach shelf supports to the wall. Thus far, I have had much better luck with the hex-headed screws (5/16″ drive) and lousy luck with Philips-headed anchors; the philips will drive within a 1/4″ of home and then spin. I’m using a Makita 18 volt, lithium ion impact driver to power the screws.
I’ve drilled a number of extra holes trying to get it right but I’m thinking it’s the old concrete. Maybe someone with experience has a better understanding of what’s going on?
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You might want to compare the two screw types, side-by-side. It may be that the Phillips screws have a broader "neck", eg, and that is hanging up as it enters the pilot hole.
Of course, with concrete screws a lot has to do with the fine details of how the threads are cut. Some will "bite" much better than others in certain substrates.
Both anchor screws are Tap-con, same thickness in the throat. It's true the Philipps-headed screw tapers slightly under the head but the screws are stopping shy of that. I'm just going to go with the hex-head and use the whole damn box of Philipps-headed screws for new concrete.
Thanks.
You need to clear the holes before you drive the screws and you might want to dril a bit deeper. Drill the hole in one move, don't take the bit out then back in as that creates a hole too large for the screw. Also, Tapcons lose about half their holding power if you take the screw out and put it back in.
I have had the best luck driving TapCons with a regular 18v drill driver and not an impact. The impact starts and stops and at each stop the dust will consolidate and tend to stop the screw from moving.
Interesting...I tried the drill driver (on "screw" setting (screw icon)) with no luck. i have found better luck with a fully-charged impact, particularly for the last inch. The hex anchors are working out now, thankfully; I would not go back to the philipps head screws but if I did, I might countersink the head, although it adds an extra step. I've been winding onto the hexes with the impact and trying not to release the trigger until the head has dimpled the wood.
I have cleared my holes by reversing; short of using air, only so much can be cleared with the piece already in place-but I'm getting the full 4 1/2" of hole.
I wonder if any of you still have any call for wedge or expansion anchors?
Reversing doesn't clear the hole.
Why such deep holes? Max embedment for the normal blue tapcons is 1-3/4 inches. Hole depth needs to be1/4" beyond that, so 2" min. Anything much beyond that is a waste of time & energy, and increases the possibility of abbrading the working part of the hole to a larger diameter. Tapcon strength is very sensitive to the hole size.
Correct about hole depth; I should be 1 1/2" in the concrete with 1 1/2" hole in the wood, for 3" total-for 2 3/4" screws. Thanks.
Reversing is probably not the best way, with risk of increasing hole diameter as Catmandeux points out. With the piece in place, I guess the only option really is compressed air.
You might think about the fact that with a Phillips head screw you're naturally going to apply more pressure to the screw, vs letting it just "drive itself" with the hex head. This might cause the dust in the hole to be pushed forward vs augered out.
the key word is "older cement" (concrete)
If it's "old concrete" it is likely to be harder (even, much harder) than a more recent pour. A hex-head tapcon is much easier to drive than a phillips head. And be sure your driver has ooomphfff! I typically use an electric driver for this specific task. Watch for torque; you can hurt yourself.
Mel froscarpentry.com
I used some Tapcons on a project and found out that they are considered Medium Duty......will this be strong enough for your shelves?