We sometimes use combination screws in our life, but do you know anything about combination screws?
Combination screw is a screw with a spring washer and a flat washer by rolling the thread, the combination of fastening together the parts of the combination. And two combination screws is a screw with only one spring washer or only with a flat washer, but also only with a flower thread of the two combination parts.
Combination screws national standard number with GB9074 representation. The commonly used cross slot small pan head three combination screws national standard number is GB9074.8. which is often referred to as the head size of pan head screws. Professional combination screw manufacturers, the customary way to indicate the triple PM. and commonly used cross slot large pan head combination screw national standard number is GB9074.4. professionally called large pan head combination screws. Or R-headed, or B-headed. That is to say, the head of this combination screw than the head of the small pan head combination screw to be larger and thicker. There is also commonly used a combination of hexagonal screws, this is a cross hexagonal combination screws. Often referred to as the cavity hexagonal combination screws. The national standard number is GB9074.13.