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Screw specification definition and understanding
One. Thread type:
A: Triangular thread (60 degrees): Union/locking
B: Is effective the triangular thread (55 degrees): Union/locking
C: Acme thread (30 or 29 degrees): Power drive
D: Square thread (90 degrees): Power drive
Two. Commonly used screw type:
A: Machine Screw: Mechanical screw
B: Tapping Screw: (A minute use with uses from the tapping in metal in plastic two kinds)
B-1: Sheet Metal Tapping Screw. (hard thread chaser from tapping)
B-2: Plastic Tapping Screw. (plastic uses, from tapping)
C: Wooden Screw: Carpentry screw
D: Drywall Screw: Cement wall screw
Three. Common screw material quality:
a.Low Carbon Steel: Low-carbon steel
b. SS-304: Stainless Steel 304
c. SS-302: Stainless Steel 302: Structure toughness is good
d. Aluminum 5052: Aluminum alloy 5052
d. Brass: Brass
e. Bronze: Bronze
f. UNS C11000 Copper: Stibium copper
Four. Common screw specification and indication:
A: Metric system screw
B: US gauge screw
C: British system screw
A: Metric system mechanical screw: Metric
Ex: M3 x 6 - P P B: The M3 mechanical screw, 6mm is long, the cross, the circle flat head, plates black.
Finish Code: Outward appearance processing specification
Head Code: Forehead outlook
Thread Code
Screw model Drive Code: The forehead splits the ditch, the characteristic model
Length Code: Screw length (mm)
A-1: Thread Code: Screw model
Metric system screw directly by screw outer diameter indication screw model,
If M3 is the screw outer diameter is 3.00mm. ; M4 is the screw outer diameter is 4.00mm.
Metric Thread Size x Pitch:
Note: The metric system screw behind the screw model, will sometimes indicate the screw to pitch.
If M3x0.5, M4x0.70, M5x0.8, M6x1.
But because the standard standard, usually does not raise.
A-2: Length Code: Screw length:
The metric system screw, indicates the screw length, the unit is mm directly.
Total length of indication the screw, only calculates below the forehead the length, does not contain the forehead altitude.
But the grub screw exception, total length of indication its screw contains the forehead altitude.
A-3: Drive the Code/forehead splits the ditch, the characteristic.
Generally the commonly used specification is as follows:
a. Slotted: A character (Minus)
b. Phillips: Cross (Plus)
c. Phil-Slot: A character/cross
d. Hex Scoket: In hexagon
e. One Way: Unidirectional (only may lock into, may not withdrawal)
A-4: Head Code/forehead outlook.
Generally the commonly used specification is as follows:
a. Flat: After flat head (locks into, crown and piece of work flush)
b. Oval: Salad head
c. Round: Round head
d. Pan: Circle flat head
e. Truss: Great-circle flat head
f. Hex: Hexagonal head.
A-5: Finish Code/outward appearance processing.
Generally the commonly used specification is as follows:
a. Z: Zine-Plated: Galvanization
b. Ni: Ni-Plated: Nickel plating
c. Tin-Plated: Tin-plating
d. Zine Plated/Green Iridite: Plates zinc green membrane processing.
e. Radiant Plated: Plates all colors
f. Passivate: Oxidation resistance processing.
g. Alodial Finish: Non-outward appearance processing
Metric system from tapping: Indicates Tapping Type directly behind the commodity name.
Ex: M3 x 6 - PPB, Tapping Type:
M3 from the tapping, 6mm is long, the cross, the circle flat head, plates black.
Generally take the product either the indication, again the judgment as Sheet Metal or the plastic department use.
B: US gauge screw.
a. generally by designation indication, like #2-56, #4-40, #6-32, #8-32, #10-24… etc.
b. or indicated by the British system outer diameter,
If 0.086-56, 0.112-40, 0.138-32, 0.164-32, 0.190-24…etc.
Ex: 632 - 8 - P P B:
Finish Code: Outward appearance processing specification
Head Code: Forehead outlook
Drive Code: The forehead splits the ditch, the characteristic model
Length Code: Screw length
Thread Code: Screw model
B-1: Thread Code: Screw model
Generally the commonly used specification is as follows:
a. #2-56 (0.086-56): 2 56 teeth
b #4-40 (0.112-40): 4 40 teeth
c. #6-32 (0.138-32): 6 32 teeth
d. #8-32 (0.164-32): 8 32 teeth
e. #10-24 (0.190-24): 10 24 teeth
the *** tooth is each 吋 tooth number. ***
B-2: Length Code: Screw length
The US gauge screw length must pass through the conversion, is the metric system mm size.
Reduction formula: (Length Code/32) x 25.40 = metric system length mm
B-3, B-4, B-5: The indication way and the metric system are the same.
C: British system screw:
C-1: Thread Code:
The indication all the denominator is 8, again designation of the direct name member.
Ex: 1/8 x 0.50 - PPB: 1 point tooth screw x 0.50” are long, PPB
Ex: 5/16 x 0.50 - PPB = 2.5/8 x 0.50-PPB: 2 divide in half the tooth screw x 0.50” to be long, PPB
Ex: 5/32 x 0.50 - PPB =1.25/8 x 0.50-PPB: 1 cent 2 thousandth half screw x 0.50” are long, PPB
Ex: 1/4 x 0.50-PPB= 2/8 x 0.50-PPB: 2 point tooth screw x 0.50” are long, PPB
Note: Sometimes will indicate the coarse thread or the fine thread.
UNF: Fine thread: Electronics industry is commonly used.
UNC: Coarse thread: The heavy machinery structure is commonly used.
Ex: 3/8 x 0.50, UNF - PPB: 3 point fine thread screw x 0.50” are long, PPB.
C-2: Length Code:
For the British 吋 indication, must be multiplied by 25.40 conversion is mm.
