On Tue, 14 Oct 2008 02:32:14 -0700, wrote:

One thing though: without the shank and the pilot hole, do they allow
the things being fixed to pull together as the screw is tightened?

If you're screwing thin to thick, and the pull-up distance is small,
then yes. The force of an impact driver helps, as does the self-
countersinking action of the screw.

However if you're pulling something into shape, best to clearance drill
the attached part.

If it's decking/chipboard/roofing to metal, look at the ???* screws.
Pilot hole in the steel, clearance in the wood, self tapping and
countersink all in one shot. Saved me ages when putting a conservatory
floor on a steel frame.

* Balls. I just went to look up the name and I couldn't find them
anywhere. dead clever design - had a drill point on the end with steel
'wings' - the wings drilled the clearance hole in the wood, then snapped
off/folded flat when they got to the steel. The drill point then did a
pilot hole until the start of the self tapper hit then it pulled itself
in. Flanges under the head then self-countersunk into the chipboard and
pulled *tight*.

Anybody know what they were/are?