I've been asked to anchor aluminum threshold
for commercial doors. About six inches wide, and
runs the width of two 36 inch steel doors. One
half of the threshold is loose, and needs maybe
four or so anchors.
Some how, I remember some blue anchors that look
a bit like drywall screws, but have really aggressive
threads. Anyone know what I need for the job?
Where to find these? Lowe's? Need flat head, so as
not to be a trip hazard. Can't have hex heads.
They are called "concrete screws"
I use them all the time and they are great. Most any H/W store will have
them. (They come in either flat head or hex head)
BTW: Don;t get the ones made out of concrete though (yes another one of
my stupid jokes)
As others have said, Tapcon is a common brand of concrete screws. If you
haven't used them before, you might want to try them in a similar situation
to your job before you try them in "real life".
There are 2 types. Flatheads, for which you should countersink the
threshold, and hex head which will end up with the head proud of the
threshold. You might not want that, unless there's a track or groove that
will keep them below the surface.
One key tip: Tapcons are essentially a one shot deal. If you spin them in
too fast you can strip the hole. Once you do that, you can't use that hole
again unless you fill it with epoxy or something. You also usually can't
loosen the fastener and tighten it again. Concrete isn't as forgiving as
wood in that regard. It's basically "a screw them down tight and leave them
I mention all this because the fasteners will be visible. If you mess one
up, you might have to drill another hole in the threshold which will also
Check out this video:
No, you can take the Tapcon out, and put 2 or 3 tooth picks in the hole
and drive the Tapcon back in. The toothpicks will act just like a
plastic or lead anchor, pressing against and gripping the rough sides of
the hole with soft wood that the Tapcon screw threads will also grip
well. Clear any dust out of the hole with a pipe cleaner first, cut the
toothpicks to length, and insert them pointy side up so that the screw
point automatically finds it's way in between the inserted toothpicks
for a uniform grip all around the screw.
While a toothpick might work in concrete for some period of time, I
wouldn't trust it as much as I would in wood. As I'm sure you know, it is
standard procedure is to use treated wood when there will be contact with
concrete. Why? Moisture.
Maybe I might consider slivers of PT wood if I had to R&R a Tapcon, but I
wouldn't trust a standard kitchen toothpick to last in concrete,
Actually, that might not be a bad idea.
Of course, in my lifetime I don't recall ever having to take a Tapcon out
and put it back in. Anything I've attached with a Tapcon was meant to be
permanent, like a sill plate to a concrete floor, wire mesh for parging
cement block, etc.
Now, I have stripped one or two while installing them, but since they were
eventually going to be hidden, I simply drilled another hole nearby and
BTW.. I just found this in a FAQ at the website listed below. My assertion
that Tapcons were a one shot deal was based on my experience, not on
anything I had read. I'm glad I found something to substantiate my comment.
Are these cement screws removable?
Yes, they are removable from the hole in which they are installed. However,
reusing the screw in the same hole is not advisable because the holding
values may be decreased or non-existent.
- See more at:
Of course, using some sort of material to improve the "holding values"
might work. Luckily I've never had to try anything like that.
On 12/26/2013 11:26 AM, email@example.com wrote:
Cut to length, for the hole? Now you've got a great idea.
I did buy some Tapcons, and two masonary bits. Looked at beeswax, but
it's $5.49, so I'll try candle wax instead.
A friend loaned me an impact driver, so I can rattle the tapcons in.
Job set up for sometime Friday, see how it goes.
My father used to use a little plastic tube-like cylinder maybe 1/4 inch
diameter about 2 inches long that inserts into the existing hole. Then the
screw would easily go down the plastic piece, expanding it to grip the
sides. He never used anything but smooth round holes in the concrete,
except for nail gun stuff.
maybe some plastic tubing would work and be more available to you.
On 12/24/2013 11:47 PM, firstname.lastname@example.org wrote:
You can get the dual tube anchor adhesive from the industrial supply
house or what I've used for big screws and bolts which it the glass
capsule epoxy that you put into a cleaned out hole then install the
anchor using a drill attachment that breaks the glass tube containing
the epoxy and catalyst which mixes and spreads inside the hole around
the anchor. The epoxy is stronger than the concrete. Hilti uses a
plastic capsule but a number of manufacturers sell a dual tube system
wkich uses a long disposable mixing nozzle. ^_^
One of the best things to turn in tapcons is a brace with appropriate
bit...plenty of leverage, lets you turn in slow and to the proper torque,
That's particulatry important with a threshold because if you torque too
much you are going to deform the (probably) hollow threshold (unless it has
a support under it).
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