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trosenda 01-12-2011 11:04 AM

Tapcon drill bits- not the right size
 
Hi,

Just a warning for those of you using tap 3/16" concrete anchors. I just purchased 300 3/16" by 1 3/4" screws to attach a subfloor to the basement slab. The first box had a drill bit that worked just fine that measured correctly (just over 5/32) subsequent boxes had drill bits that measured over 11/64th which caused the screws to just spin in the holes :-( A little irritating when you try to get 20 pre-drilled holes ahead before adding screws.

My recommendation is to check the drill bit diameter in the tapcon box before using them.

Mr Chips 01-12-2011 11:17 AM

Quote:

Originally Posted by trosenda (Post 568454)
My recommendation is to check the drill bit diameter in the tapcon box before using them.

You should be fine if you use a bit that was designed for concrete screws. A 3/16 tapcon bit is made to tighter tolerances than a standard ANSI drill bit. Sometimes if your concrete is really dense you might be able to get the screws to bite with an ANSI bit, but keep in mind that the manufacturers published holding values were obtained using the correct bit

While on the topic of concrete screws, it's also good to keep in mind that most "blue screws" have a maximum embedment of about 1-7/8" in concrete. They will typically start to bind beyond this depth and you'll usually end up snapping or stripping them

trosenda 01-12-2011 11:41 AM

The point is that the drill bits are larger than the drill bits in a previously purchased box of tapcon screws. Because the old drill bit was smaller and working just fine and new larger drill bit is not, I assume the new bit is in fact too big.

Nucon 01-12-2011 12:44 PM

"While on the topic of concrete screws, it's also good to keep in mind that most "blue screws" have a maximum embedment of about 1-7/8" in concrete. They will typically start to bind beyond this depth and you'll usually end up snapping or stripping them[/quote]"


I use tapcons alot on commercial project. For instance Wal-Mart requires their parapet blocking attached with 1/4" x 4" tapcons. That's roughly 3" embedding and they hold like a kung-fu grip. I use a 3/16" SDS Plus bit. No snapping or stripping.

canadaclub 01-12-2011 01:48 PM

I had a similar problem when I bought a pack of Passlode 2" brad nails. The top layer worked just fine but the remaining slips were all about 1/64" (if that) thicker and kept jamming my gun. The difference was so slight so I just assumed my nailer was at fault. Took them back to HD and they opened up other boxes and found the same thing. You would think they would at least give me a free pack for my time and trouble, but noooooooooooo:whistling2:

Mr Chips 01-12-2011 01:56 PM

Quote:

Originally Posted by Nucon (Post 568507)
I use tapcons alot on commercial project. For instance Wal-Mart requires their parapet blocking attached with 1/4" x 4" tapcons. That's roughly 3" embedding and they hold like a kung-fu grip. I use a 3/16" SDS Plus bit. No snapping or stripping.

It all depends on the base material. If you look at the manufacturer's specs, they usually show data up to 1-3/4" embedment. That's because the screws really don't have a way to get the dust out of the hole at deeper embeds ( hence the binding, stripping, and snapping). If you are going into grout filled CMU or lightweight concrete you can probably get deeper embeds, but most manufacturers will recommend no more than 1-7/8". You might want to check it out, especially if you are doing commercial work and are exceeding the published max depth. You could be opening yourself up to liabilty (DISCLAIMER: I am not a lawyer, YMMV)

EDIT: from the TAPCON website:
Tapcon anchors require a minimum embedment of 1" and a maximum embedment of 1-3/4".

From the Powers Fasteners Tapper spec sheet:
Do not select a length that will result in an embedment into the base material which is greater than 1-3/4" to 2". Most concrete screw anchors cannot be properly driven to a depth of more than 2", especially in denser base materials.

Nucon 01-12-2011 02:04 PM

Good Info Mr. Chips. By spec were required to clean the hole before inserting the tapcons. Mostly we use a Hilti bulb. Usually were drilling filled CMU/TUCP or high strength slabs.

Mr Chips 01-12-2011 02:45 PM

Quote:

Originally Posted by Nucon (Post 568586)
Good Info Mr. Chips. By spec were required to clean the hole before inserting the tapcons. Mostly we use a Hilti bulb. Usually were drilling filled CMU/TUCP or high strength slabs.

It's not so much the dust from drilling that's the issue ( if it were you could just drill deeper and create a dust pocket) but it's the dust ( and friction) from the the screws cutting threads during the installation. If someone higher up the food chain is spec'ing a 3" embed in cleaned holes, you arse is probably covered, but it never hurts to know!


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