Self-Countersinking Screws

      The pros and cons of screw-head "knibs." June 22, 2005

In both assembly and installation I use square drive, auger point screws as much as possible. But I do not like the self-countersinking nibs on the heads. The screw just does not seem to pull hard enough. I cannot find a supplier that carries auger tip bugle head screws without the self-countersinking head. Is there such a screw available and if so, where can I find it?

Forum Responses
(Cabinetmaking Forum)
Try Kreg Tool Co. They have a good variety and good quality. They offer nearly all of their screws with a washer head that will not countersink.

You will be asking for a "type 17" without nibs. We use the type 17 with nibs and don't have problems. It seems to pull the material together just fine. What kind of material are you using?

From the original questioner:
We use all the typical material and hardwood species used in cabinetry and furniture. Let me give an example where the typical type 17 with nibs is not satisfactory. If I am fastening two identical pieces of wood together, drawing one tight to the other without countersinking, the screw will usually continue to countersink into the wood before it has adequately drawn the two pieces together (I guess that is similar to fastening two face frames together - another situation I am not satisfied with. I do pre-drill face frames with a tapered bit, but still, many times the screw sinks too deep before the frames are drawn up tight.) I just don't see the point of the nibs. Without the nibs, the screws will still sink flush to the surface and you have twice the pull.

Are you using pocket holes and are these pocket holes being drilled with the proper drill bit (the correct size) and depth? Could your pilot hole be too shallow (not all the way through) or too large, allowing the screw head to pull into it? I'm not sure, but I think the nibs under the head are to help prevent the screw from backing out.

You don't want self-sinking nibs in pocket holes. Pan head, auger tip for that. For ply to ply, I use type 17 with nibs in a Senco Autofeed without problems.

Two things you might try. First, use an oversize bit (large enough to keep threads from grabbing) to pre-drill through the first piece of wood. You want the threads to grab the second piece and draw it tightly to the first piece. Second, clamp the pieces together before screwing. This will prevent the screw from pushing the second piece away before grabbing and drawing tight.

From the original questioner:
I understand all those basic concepts. I just cannot see the point in having the nibs. They do nothing but minimize the pull of the screw. This might seem like a minor detail, but it really bugs me that I can't find a plain old 2 1/2" screw (for instance) with auger point only! This is North America, for cryin' out loud. I think I'll hire a guy to file the nibs off, one screw at a time. A professional de-nibber. Or maybe it would be quicker to buy regular screws and have him grind an auger tip on the end.

I think the real reason for the nibs is it keeps them from snapping off. Hence there is less pressure on the screw.

The nibs are to prevent backing out, not countersinking. If they were for countersinking, they would have channels to allow the chips to evacuate.

How big are the shoulders on your screws? Are they long enough to go past the first piece of wood? I clamp my wood or if I drill without a pilot hole, I sink it close to the head, then back it out, and then get the pieces together and drive it home. What speed are you driving these? I use high speed on the cordless, a cordless and pneumatic impact - both fast speeds.

If the nibs are to prevent the screws from backing out and running away, then some of my suppliers are mis-advertising. If the nibs are to prevent the screws from breaking off, then why don't the truss head installation screws that have no nibs ever break off? They are absolutely, positively called a self-countersinking head. These type 17 screws are also advertised as "no pilot hole needed". This is only true if you clamp the two pieces prior to screwing them together, in which case a pilot hole is much quicker.

I've done the research and exhausted all the various means and methods available, none to my complete satisfaction. That is what inspired this post. My original question was " there such a screw available (auger tip/no nibs) and if so where can I get them?"
I do thank everyone who has taken the time to give input. It's been very informative.

Deerwood and Quickscrew both make a type 17 point, coarse thread, combo recess (square/phillips), nibbed head nickel finished screw that works great for us for plywood box assembly. The 2" length has no threads for a good 3/4" below the head, which allows the screw to pull the parts together as the screw is driven home and sunk just below the surface. The only improvement I would like to make is using a cordless impact driver to run them in. Any recommendations out there?

I've just switched to impact drivers the first of the year. They are a lot easier on the body. I use a Makita 14.4 amp. These drills drive the nibbed screws right through solid oak! The other day I was installing a pantry cab with a 1/2" truss head screw and inadvertently drove it right through the back (I was talking to my helper).

I use a Dewalt 14.4 and a pneumatic. The pneumatic is fast, sometimes too fast. It will spin the screw before it begins to bite. I chose the 14.4 because of the weight. No need to heft around an 18v monster. Works good for me. Some have suggested the Panasonic. I think the only drawback is the bit that you can use with it - I think you have to use their bit.

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