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Re: how thick steel angle ok for self tapping screws?

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> From: "Haan, Scott M POA" <Scott.M.Haan(--nospam--at)poa02.usace.army.mil>

> How thick of a steel angle can #10 or #12 self-tapping screws be
> connected to?  I have normally seen people use powder driven fasteners for
> connecting stud clips to steel angles but have recently seen a detail
> using self-tapping screws.  It seems like it would be pretty labor
> intensive screwing deflection clips to a steel angle.

Scott,
Simplistically, the length of the unthreaded drill point determines the
thickness capability of a self-drilling fastener.

ITW/Buildex makes the TEKS (tm) self-driller which is the common brand
name. The #5 or Tek5 will handle up to 1/2" total thickness. Lower
number = shorter drill point. So a Tek5 - #12-14 x 1 1/4 has a 1/2"
drill point, #12 diameter (0.21"), 14 tpi and 1 1/4" threaded (total 1
3/4" under head).

To complicate things, the strength of the drilled material limits the
ability to drive the threaded portion without torquing the head off. As
a result, the smaller diameter fasteners are not available with the
longer drill points.

Conversely, the larger diameters can't get efficient grip in thin
material and are not commonly available with the short drill points.

It is essential to match the max thickness to the drill point. The drill
tip MUST penetrate all plies before the threads engage. It is possible
to use oversize punched or pre-drilled top layer(s) to avoid engaging
the threads too early and achieve a thicker connection because only the
bottom ply is tapped. The manufacturers provide recommendation tables.

Minimum Teks/3

-- 
R. Paul Ransom, P. Eng.
Civil/Structural/Project/International
Burlington, Ontario, Canada
<mailto:ado26(--nospam--at)hwcn.org> <http://www.hwcn.org/~ad026/civil.html>

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