7" Tapcon Drill Bit Wobbles?? - Tools - DIY Chatroom Home Improvement Forum

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Old 06-21-2011, 04:44 PM   #1
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7" Tapcon drill bit wobbles??

At my wits end here!

I'm trying to install some shelving in a closet. Most of the walls in my house are plaster over concrete brick or plaster over concrete block. One wall in this closet has several layers of strange stuff (I'm guessing drywall and plaster) with no hollow areas that would allow a normal molly bolt to expand. Therefore, I've had to buy 1/4" x 3-3/4" Tapcon concrete screws that will hopefully reach the concrete block or concrete brick that I believe to be behind the layers of strangeness.

Naturally, I had to buy a corresponding drill bit. Got the Tapcon branded SDS drill bit size 3/16" x 7" and was excited to finally get this project finished.

Tightened the drill bit into my Makita drill (it is a one-speed but has a hammer drill option) and gave it a whirl only to find that there's a huge wobble at the tip of the drill bit! I can't remember any of our other drill bits ever having this issue. I noticed that the drill has 3 prongs that hold the drill bit (is that called the chuck??), but the drill bit itself is constructed with 4 "sides", and I'm wondering if this discrepancy is causing the issue.

My husband thinks it doesn't matter, and we should just go ahead and use it as is ... but isn't this wobble going to make the hole too big for the screws to then work properly??

Do I go ahead and use the bit anyway, or try to take it back to the store and get a straighter one, or maybe a different brand (though I don't recall seeing other 7" bits in the display)?

Help, anyone?


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Old 06-21-2011, 05:24 PM   #2
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The "SDS" bits are a special masonry bit that typically requires a special rotary hammer (hammer drill on "steroids"). They can be chucked into a typical style 1/2" drill chuck, you may just have try it in a few different spots. Meaning, if it wobbles now, try loosening the chuck, turning the bit a little bit, and re-tighten, then check to see if it runs true.

If it still wobbles, it should work fine. It will stabilize as it starts to hit harder material in your case the concrete block.


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Old 06-21-2011, 09:25 PM   #3
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^^^He's right^^^ My solution would be: If your buying at a bix box store, the tapcon bits are generally located next to the tapcon screws, so it appears that these are your only option. I would return that bit and find a 3/16 masonry bit for a standard 3 jaw chuck that generally will be located with the other drill bits. Bosch makes excellent masonry bits(in many lengths) that are more effective and last longer in my opinion.
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Old 06-22-2011, 04:51 PM   #4
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Funny, I did exactly what you suggested, jomama, before I even saw your reply. I loosened the chuck, then brought the drill bit outwards, rather than setting it all the way into the chuck. Had to fiddle with a couple of different positions, but finally got it to where the wobble was considerably less (though it wasn't eliminated completely). Husband then insisted we at least try it out... he drilled the pilot hole and was able to use a regular Phillips driver (rather than attaching one to our drill) to drill the Tapcon screw all the way in, with less trouble than the ones we did on a previous wall (where I suspect we didn't drill the hole deep enough or didn't clean out the dust enough). I'll try to give another update once I load the tracks with the standards and shelves that I bought, and see how much weight these puppies end up holding.

If I wasn't pregnant, I'd probably be more patient when it comes to looking for the best quality drill bits. But I do appreciate the input on Bosch bits, SoCal, and will keep that in mind for future purchases!!
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Old 06-22-2011, 08:54 PM   #5
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Quality control on box store stuff is not the greatest and drill bits are not checked out the way they should be. Your new bit may have a shaft that was never true to start. I would take it back for a new one. A sharpening shop might be able to true yours up but it is kind of silly pay for such servicing on a brand new bit?
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Old 06-30-2011, 06:47 AM   #6
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Most Tapcon bits made to be used in a 3 jaw chuck are tanged on the end, meaning they are round with a little flat side at the very end. If your bit has a bunch of flats on it, but is round with indentations above the flats, you most likely bought an SDS bit ( the flats are for using an adapter that slides over the bit and drives the screws).

Tapcon bits are made to tighter tolerances than standard bits, so you will get the best results using a bit that is made for concrete screws. If you use a regular ANSI standard 3/16 bit instead of a 3/16 concrete screw you run the risk of stripping out the holes a lot easier. My recommondation is to go back and look closer for the proper bits.
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Old 08-17-2011, 09:53 AM   #7
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SDS drill bits are built to be used in a SDS chucked drill but they can be used in a standard 3 tong drill chuck. You just need to get it seated properly and the wobble will stop. Loosen the chuck and rotate the bit a little and then tighten the chuck until you get the bit to rotate smoothly. Most cordless drills have a hammer function, which is not as powerful as a roto hammer but will still get the job done. Good luck.


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