Self drilling screws are OK for conduit clamps, wire clips and other
miscellaneous uses but I would never recommend them for anything structural.
Drill points on screws are not going to be accurate nor the drilled holes
clean. And threads that cut into those holes won't be strong. Holding
strength comes from correct thread mating, it's friction from thread contact
that keeps it in place.
Look at this spec sheet for 1/4" stainless self-drill screws and you see
that it's only 14 threads per inch, not 20.
http://www.fastenersuperstore.com/productSheets/SelfDrillingScrew.pdf
Self tapping screws, the ones with the 3 sided thread forming ends and hex
head are nearly as good as a properly tapped hole in aluminum. A #7 (.201")
split-point stub (aircraft) drill will drill thru a 1/4 of aluminum in 1 to
2 seconds without walking. A 1/4-20 screw will cut threads the entire length
of the hole and the screw will not come out.
In my previous life as a machinist for almost 20 years, a few things have
stuck with me like the importance of proper cut threads. Besides, driving
home a self-drilling screw will run down drill batteries a lot quicker than
a sharp drill bit.
my 2cts....
Jim Duncan
North Texas Renewable Energy Inc
817.917.0527
nt...@earthlink.net
www.ntrei.com
----- Original Message -----
From: "jay peltz" <j...@asis.com>
To: "RE-wrenches" <re-wrenches@lists.re-wrenches.org>
Sent: Friday, October 23, 2009 10:18 AM
Subject: Re: [RE-wrenches] SS Tek Crews
HI Guys,
Check out dynamic fastener,
they have a lot of great stuff.
Including self drilling 1/4x 20 SS screws and larger.
jay
peltz power
On Oct 23, 2009, at 3:12 AM, Carl Adams wrote:
Hello Wrenches,
Pulling up this thread from earlier in the year. I have a couple of
upcoming jobs where I am attaching PV mounting structure as follows
Job 1) LFoot to metal roof into Z purlin, and Job 2) FastJack to metal
roof into bar joist.
In both of the applications I'm considering the Tek screw type
attachment to the building steel. Both the L foot and FastJack are
sized for a 5/16 - 3/8 lag or bolt. Most of the self tappers I see
are 1/4" max diameter. Should I be concerned about the undersized fit
of the fastener in the mounting attachment or are there large Tek type
screws out there I'm not finding?
Does anyone have pullout strengths for this type of attachment?
With Regards
Carl Adams
NABCEP Certified PV Installer
SunRock Solar, LLC
On Thu, Feb 5, 2009 at 6:51 PM, Peter Parrish
<peter.parr...@calsolareng.com> wrote:
Does anyone have a source for stainless steel, self tapping Tek screws?
I
could use some #10/3-4 and #10/1-1/2. If they have the little cap and
neoprene washer that would be even better!
- Peter
Peter T. Parrish, President
California Solar Engineering, Inc.
820 Cynthia Ave., Los Angeles, CA 90065
Ph 323-258-8883, Mobile 323-839-6108, Fax 323-258-8885
CA Lic. 854779, NABCEP Cert. 031806-26
peter.parr...@calsolareng.com
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