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Screw common specifications and common categories

usual format
A: Metric screws B: American screws C: British screws
A: Metric machine screws: Metric
Ex: M3 x 6 – P P B: M3 machine screw, 6mm long, cross, round flat head, black plated.
Finish Code: Appearance processing specifications
Head Code: The appearance of the head.
Screw head shape. Cylindrical head. Half-sunk head. Sink head. Spherical cylindrical head. Pan head. Half round head. Hex Head.
Screw head shape
Thread Code
Screw model Drive Code: head section groove, characteristic model
Length Code: Screw length (mm)
A-1: Thread Code: Screw model
Metric screws directly indicate the screw model with the screw outer diameter,
For example, M3 means the outer diameter of the screw is 3.00mm.; M4 means the outer diameter of the screw is 4.00mm.
Metric Thread Size x Pitch:
Note: Metric screws are at the back of the screw model, and sometimes the screw pitch is indicated.
Such as M3x0.5, M4x0.70, M5x0.8, M6x1.
But because of the standard specifications, it is usually not mentioned.
A-2: Length Code: Screw length:
Metric screws, directly indicate the length of the screw, the unit is mm.
The total length of the screw is indicated, only the length below the head is calculated, without the height of the head.
The exception is for flat head screws, where the total length of the screw includes the height of the head.
A-3: Drive Code/ head section groove, features.
Common categories
Various common screws
Various common screws (20 sheets)
a. Slotted: One word (Minus)
b. Phillips: Cross (Plus)
c. Phil-Slot: One word/cross
d. Hex Socket: Hex socket
e. One Way: One-way (can only be locked in, not exited)
A-4: Head Code/ Head shape.
a. Flat: Flat head (after being locked, the top is flush with the work piece)
b. Oval: Salad head, O head, semi-sunk head
Screw measurement unit
c. Round: Round head
d. Pan: round flat head
e. Truss: Big round flat head
f. Hex: Hexagon head.
A-5: Finish Code/Appearance processing.
Metric self-tapping screws: mark the Tapping Type directly behind the product name.
Ex: M3 x 6 --PPB,Tapping Type:
M3 self-tapping screw, 6mm long, cross, round flat head, black plated.
Generally use product type or label, and then judge as Sheet Metal or plastic parts.
*Tooth pitch = number of teeth per inch
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