Thread cutting screw capacity

[bnickeson]

We have a client that wants to install aluminum cantilevered sunshades attached to the face of steel tube columns. They'd like to use 3/8" thread cutting screws (such as these: Link ) to fasten the outriggers to the column walls. I cannot find any information at all on the tension capacity of these. Does anyone have any information on load capacities for thread cutting screws?

Our column walls are 1/2" thick so they have plenty of bite, and given the tension capacity for 1/4" self-tapping screws into 1/8" material is around 380 pounds, I think we should be OK. But the repetitive change in force on these due to wind has me a bit concerned to use nothing more than screws.

 

[jjl317]

In terms of this type of fastener, I believe the Dewalt Tap-Flex is similar, and has technical information.

If exterior, personally I would be looking at 300 stainless steel as the material, for both general corrosion resistance, and better performance as dissimilar metals.

One product we often use if the Elco/Dewalt Bi-Flex - created with two metals (a hardened steel tip for cutting, then a more ductile body) - 300 series stainless, plus coated for corrosion resistance, and can documented for use into 1/2" thickness steel. However, I believe only available up to 1/4" diameter.

Finally, for what it's worth, it's pretty common that cladding connections exposed to wind are attached only with screws.

Hope this helps

 

[bnickeson]

Perfect! That's exactly what I'm looking for. Thanks.

This is being installed on the interior side of the wall, and the outrigger attachment is steel so we don't have any issues with corrosion or dissimilar metals fortunately.

 

[jjl317]

FWIW, the Elco/Dewalt Dril-Flex has a similar make-up (a hardened steel tip for cutting, then a more ductile body) to the Bi-Flex, but is Carbon Steel (plus goes up to 5/16" diameter).