DIYbanter - View Single Post - Self-aligning screw thread?

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posted for all of us...

On Mon, 18 Feb 2019 22:46:25 -0500, Clare Snyder
wrote:

On Mon, 18 Feb 2019 19:08:44 -0700, rbowman
wrote:

On 02/18/2019 08:38 AM, Commander Kinsey wrote:
They shouldn't call them self tapping because they rarely do unless the
wood is very soft indeed. Usually the force to create the hole wears
off the er.... the bit the screwdriver goes into. I almost always use a
pilot drill first, unless I'm in a hurry, then I curse the bloody screws
when they burr.

Using the correct size of a quality screwdriver helps. What is the UK
equivalent of Harbor Freight?
"Self drilling" is the term, and if they aren't Chinese junk they are
usually good for 16 guage steel - perhaps 14. Useless foir anything
heavier. Chiners junk is good for about 18 guage aluminum on a good
day.

Actually there are at least four types of screw that cut their own
thread.
You have the self drilling that is a sheet metal screw with a drill
bit tip on the end that actually drills the pilot hole (Commonly
called Tek screws)
Then there is the self tapping sheet metal screw that just has a point
on the end and gnaws it's way in
The third is a "swage form" machine screw that goes into a pilot hole
and the tip is threaded all the way to the end with a slight taper and
a triangular shape until it gets to the body of the thread. It
actually swages threads
The 4th is a self tapping machine screw that has a tapered thread and
slits cut in it to take away the waste material just like a tap.
I have some of each type if anyone wants pictures.

Sure pix are great. I may learn something.

--
Tekkie