WHY ARE SCREW COUNTERSINKS AT 82 DEGREES?
This was contributed by Frank Shapiro who is a Canadian engineer from Ottawa, so he should know everything. The reason for this is quite neat, screws are 82 degrees, because they were meant to replace the nail. The old square nails once used as well were not 90 degrees but were indeed on average 82 degrees, and the manufacturer of screws wanted to fill the same hole and as such maintained the angle. Now why were nails 82 well that comes from how they were made, they were cut pieces of metal cut with a chisel and placed in an anvil (for making nails) and the top was hammered to give us the flat nail, and mushroom head. The Anvil had an 82 degree impression for this, although not all nails followed this convention, just the majority. Now why did the anvil have that angle, this goes back to the ancient Greeks, who when making chariots and eventually banding the wheels, were avid smokers, at that time, there were no ashtrays, so the original blacksmiths in those days drilled their anvil an
