The standard countersink angle for screws in the US is 82 degrees. In England it is 90 degrees. This small difference is significant and has caused us much head-scratching. If you attempt to install a standard English hinge with an American screw of the correct size you will find the screw head sitting too high. The root of the countersink will bottom out before the periphery. Not only will this prevent the hinge from closing completely it is also unsightly and because the contact between the screw and the hinge is limited to a small area, the hinge will loosen prematurely. The problem would be much less if the reverse was the case and an English screw was used to install an American hinge.
