On Tuesday, July 2, 2013 6:00:07 PM UTC-6, wrote:
(In the spirit of "It's better to ask a stupid question than to make a stupid mistake...) These two screws are both sold as 4mm: https://plus.google..com/photos/1127...CLGTvbqC-5LWMQ (links to four pictures, showing measurements on digital caliper of shaft & thread for each of the two screws. Hosted by google, no adverts other than what google stick in, if any) Am I right in my understanding that 4mm is the maximum size of the thread diameter, i.e. they are likely to be smaller than this measurement, but they will not be bigger? Secondly, for a pilot hole, I understand that the drill bit used should be the diameter of the shat of the screw, so it is basically the threads that are biting into the wood fibres and the screw shaft is not having to be forced in. But as the photo's show, the shafts are not of an available drill size so it is better to go for the next drill size up or down? Or round up or down either side of the half measurement? Sorry if these questions seem trivial to you all, but this sort of thing gnaws away at the back of my mind, so it's nice to get some professional input! Thanks in advance, David Paste.

Quick tip for attaching two pieces of wood together, drill the pilot hole on the board farthest from the head of the screw,with a drill bit that is smaller than the diameter of the screw. I usually go with a drill bit as close to the shaft (minus teeth)as possible without going over it. Drill the pilot hole of the board nearest the head of the screw with a drill bit that is the diameter of the teeth of the screw. This way when you screwing in the screw, the screw will float thru the first board and grab the second board, thus creating a tighter joint.