Self-Drilling Fasteners 2

[dik]

I have a new project where the client is using self-drilling fasteners to secure framing. The attachment is 3/16 material to 12 Ga. There are 4 fasteners per attachment. The loads are strictly shear and the untimate load per fastener is 2100lbs. There's no recommendation of a FOS, and I was thinking of 3, and using this as the limit load (this still has DL and LL load factors) because there are multiple fasteners for each connection. Anyone have any thoughts on the approach. Is it too conservative? I don't do a lot of work using self-drilling fasteners.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[XR250]

I think Buildex uses a FOS of 3.
Make sure you pre-drill the 3/16 or it will not pull tight.

 

[dik]

thanks... didn't know about pre-drilling... else may strip through the 12ga. FOS will be a little over 4 when the smoke clears...

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[XR250]

Are bolts a possibility? - I mean if you already have the drill out.....

 

[dik]

The attachment is loose and will be fabricated in a shop and can easily be drilled; this is not the case for the CFS purlins. Loads are too light for bolted connections and client want to use self tapping. I also don't like using bolts less than 1/2" dia. (I've seen too many 3/8" ones break). I was going to drill the attachment angle end plates with hole for #12 screw, not leaving 1/16" clearance.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[dhengr]

Dik:
If you can, you should be fastening/tightening the thinner material to the heavier ga. material. The screw head should engage the thinner material, so that stripping that thinner material doesn’t adversely affect the joint. Those screw tips are case hardened, and just plain wear out if you try to pierce through more than about 3/16" thk. stl, and the more so on harder, or higher strength stls. Read the fine print which comes with the screw testing/strength literature, and they usually do say something about limited material thickness for their fasteners.

 

[dik]

Thanks dhengr... in this case the thicker material is 3/16 end plates welded to some L3x3... so it has to be the thicker to the thinner. I'm not sure it matters with pre-drilling. The load is strictly shear.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[dhengr]

Dik:
Then, there will be a serious caution about stripping the 12ga. material before you draw it tight, even when you pre-drill the thicker piece. It only takes about 1/4 turn of the screw to really start to strip that thinner material, and the construction worker can’t/won’t set their driver motor clutch low enough to just tighten up the joint. They want speed, and could give a damn about finesse.

 

[azcats]

With regard to stripping the thinner material, why does it matter if the outer ply is 16ga or 3/16" if it's pre-drilled?

 

[dik]

Some fasteners have different products depending on the thickess of the material, for exampe TEKS 3 and TEKS 5. If predrilled, then the thinner material determines the fastener. I think I've settled into using ITW TEKS... and I will use the added 1/16" hole dia. to minimise stripping.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[IRstuff]

Is it a permanent installation? Could you use pop rivets?

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

https://www.youtube.com/watch?v=BKorP55Aqvg

faq731-376 forum1529 Entire Forum list

http://www.eng-tips.com/forumlist.cfm

 

[dik]

It's permanent and the client wants to use self tapping screws... pop rivets are a good idea, and will suggest them; it's a matter of getting load values. I last used pop rivets for strap replacement for cross-bracing at Polo Park shopping centre about 40 years ago. The contractor had not placed the angle bracing... it was a steel stud and masonry wall, and the masonry was half in place... and opening was coming up... only time I've use them and the first time for CFS and masonry....

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[dik]

I've sent a query on to pop rivet, for loads, and also to the client, for suitability. We'll let you know.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[dhengr]

Azcats:
It matters because most of these guys are using fairly powerful impact drivers, the clutch can’t be set low enough, or they don’t set it low enough, and they can’t feel when things are drawn together/tight, then another .25 or .5 turn strips the thin material, and they don’t really even know that. It is an improvement that the drilled hole in the heavier material is a little oversized, so it doesn’t show a false/added torque while driving.

 

[dik]

I will note that they cannot use impact for TEKS fasteners.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[dik]

I'm speccing 1/4" dia holes for #12 TEKS.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[rowingengineer]

I assume your using tilting and bearing analysis as per the cold formed code from your area.

In this case I was spec a deep driller, don't know if you have such a thing in your area, but in my area they have a longer tip, with class 5 finish so can screw up to 1/2 material combined layers.

We generally have to know the amount of testing to assign a sampling factor. The more tests and data the better the number.

 

[dik]

Thanks... waiting for the dust to settle before I continue.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[Tomfh]

I will note that they cannot use impact for TEKS fasteners.

Impact drivers are the tool for the job.

 

[dik]

one of the tools... The project has no HS bolts.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik