#12 screws can drill through 1/4" thick steel plate?

[VinuCG]

I have a condition in one of my steel project, where the 1/4" thick steel deck edge bent plate has to connect with cold formed truss member by means of #12 screws. Whether these #12 screws can be driven in field (self-tapping) through 1/4" thick steel material without any predrilled holes on it?

 

[3DDave]

Are these self-drilling self-tapping? They will indicate on the packaging the thickness they can go through.

Typically the drill point has to exit the far side of the material before the thread engages.

How thick is the total engagement?

 

[dik]

You might want to look at TEKS.

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-Dik

 

[Tomfh]

With steel of that thickness it’s often worth assuming that pilot holes may need to be drilled, regardless of what the screw manufacturer says.

 

[hokie66]

Tomfh is correct. I've tried self drilling screws in 1/4", without much success. Predrill.

 

[VinuCG]

Some fabricators prefers to add pilot holes for ease of job, some prefers to leave without any holes.
But my point is, self drilling/tapping screws can only used for fastening thinner materials (such as sheet metals) or it can be used for thicker materials as well? (Say 1/4" thicker or above?)

 

[hokie66]

You have some advice, but you probably won't be convinced until you try it for yourself.

 

[kingnero]

All data sheets I've seen of self-drilling / self tapping / flow drilling fasteners specifically list the material thickness range they're designed for.
Have you checked those?

 

[Once20036]

Aside from the question of "can it", you might want to consider "should it".

Let's assume that the two layers of steel are approximately the same thickness.
If you`re using a self tapping screw through a 1/4" steel plate, the threads will be locked into that plate. As the drill tip exits the steel plate and enters the cold formed truss member, it could push against the chord member, create a small gap before it starts drilling, and then create threads in the truss member. Because each layer of steel is held by the threads, there is no way to close this gap, and no clamping force will be created between the two layers of steel.
I`d suggest predrilling the plate (greater than the thread outer diameter).

I think that the situation is worse if the truss member is thinner than the steel plate. At that point, your screw capacity becomes driven by a failure of the thinner plate. Better to drive it "upside down" in this case - predrilling and driving through the thin steel into the thick steel.

 

[jgailla]

From personal experience, you can get self drilling screws through a 1/4" plate. I used to do construction labor for cold formed and red steel. It takes patience and slow use of a drill to get it through without burning out and melting the tip. I would never specify the use. You will get a change order immediately when the contractor shows you a heap of melted screws.

 

[XR250]

Tek5 will drill thru 1/4" (done it plenty on my house).
Typically though, you want to go thru the thinner material first or else it wont clamp well. I would pre-drill
Bascially what Once20036 said.

 

[Tomfh]

But my point is, self drilling/tapping screws can only used for fastening thinner materials (such as sheet metals) or it can be used for thicker materials as well? (Say 1/4" thicker or above?)

There is no definite answer. Sometimes it will work, sometimes it won’t.

It depends on the specific screw, the steel properties (higher strength steel is much harder to drill theough), your technique, how much patience you have, etc. It’s not a yes/no answer.

It can work, but you shouldn’t assume it will work, because it often doesn’t.