Usage and precautions of countersunk head screws

Countersunk head screws are used in the need to install, the surface of the parts can't be raised, and there were two kinds of thickness of the fastening parts, so-called thick, that is to say the fastening parts thickness is greater than the countersunk head screw head thickness, bolt tightening, there are some of the screw thread into the threaded hole does not, as shown in the 8th floor attached figure, this kind of situation, sink must can tighten the screw. There is usually another case, that is, the thickness of the fastening parts is less than the height of the countersunk head screw head, which is common in mechanical equipment in sheet metal parts, such as the hinge of the case and the connection of the door and box; The connection between the sheet metal cover and the equipment and so on. Due to the smaller the thickness of the parts by the fastening of the sheet metal parts, screw hole completely into a tapered hole, in this case, when the countersunk head screw is tightened, the screw head is not cone clamping sheet metal parts, but the screw head root ministry with threaded hole at the top of the crushed to death, although feel screw is tightened up, but the metal sheet is stuck not by pressure, in this case, although the feeling The screws are tightened, but the sheet metal is not. This is a very common situation.

Again processing reasons: countersunk head screw head round show 90 ° taper Angle, vertebral body usually bought new bit apex Angle is 118 °, 120 °, some lack of training workers don't know this Angle difference, often with 120 ° drill bore hole directly, this can make countersunk head screw is not head conical face difficulty, but a line at the bottom of the screw head to eat Force, this is one of the reasons why the so-called countersunk head screws don't hold, it's not the screw's fault.

Countersunk head screws for attention?

1, reaming taper should be 90°, to ensure that it is better to be less than 90°, but not greater than 90° this is a key trick.

2, if the thickness of the sheet metal is less than the thickness of the countersunk head screw head, you can change the screw of a smaller size, or rather than reaming a small hole can not reaming to make the bottom hole diameter large parts pressure is not tight.

3, if there are multiple parts countersunk head screw hole, accurate processing, once the drill slanting, assembled very ugly, but as long as the error is not completely can be tight, because in the tight, if the diameter of the screw is not very big (about less than 8 mm), pitch error, screw head in due to the stress and deformation will tighten when they are tight.