On Tue, 31 Mar 2009 15:44:45 +0100, John wrote:
If the screw has cut itself a thread in first piece and you start with a gap
then no amount of tightening will close the gap - it may be more likely to
strip out the thread in the second piece than the first. A clearance hole
(at least as big as the outside diameter of the thread) will absolutely
assure a good clamping effect

Doesn't drilling a hole that large mean that all the stress is then on the
head of the screw, rather than (with a smaller hole, or no hole at
all) being distributed along the length via the screw thread? For softer
wood in particular, won't that result in a joint that's prone to flexing
if the wood ever has the chance to wear against the screw head?

If I'm using relatively soft wood, I've always found the "tighten, back
off a bit, re-tighten" method that someone else mentioned further back to
work well - for harder wood I'd go the pilot hole route.

cheers

Jules