Common specifications for screws

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  • Time of issue:2019-09-25 21:00
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A: Metric screw B: US standard screw C: Inch screw
A: Metric machine screw: 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: Head shape.
Screw head shape. Cylindrical head. Half sinking head. Shentou. Spherical cylindrical head. Pan head. Semicircular head. Hex Head.
Screw head shape
Screw head shape
Thread Code
Screw Model Drive Code: Head section, feature model
Length Code: Screw length (mm)
A-1: Thread Code: Screw Model
The metric screw directly indicates the screw type with the outer diameter of the screw.
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: The metric screw is located behind the screw model and sometimes indicates the screw pitch.
Such as M3x0.5, M4x0.70, M5x0.8, M6x1.
But because of the standard specification, it is usually not mentioned.
A-2: Length Code: Screw length:
Metric screw, directly indicating the length of the screw, the unit is mm.
The total length of the screw is marked, only the length below the head is calculated, and the head height is not included.
The exception is the flat head screw, the total length of the screw is marked with the head height.
A-3: Drive Code/ head section, feature.
Common category
a. Slotted: One word ( Minus )
Various common screws
Various common screws (20 photos)
b. Phillips: Cross (Plus)
c. Phil-Slot: Word/Cross
d. Hex Socket: Hexagon
e. One Way: One way (only lockable, not quit)
A-4: Head Code/ Head shape.
a. Flat: flat head (after locking, the top is flush with the work piece)
b. Oval: salad head, O head, semi-sunk head
c. Round: round head
Screw unit
Screw unit
d. Pan: Round flat head
e. Truss: big round flat head
f. Hex: Hex head.
A-5: Finish Code/Appearance Processing.
Metric self-tapping screws: Directly mark Tapping Type.
Ex: M3 x 6 –PPB, Tapping Type:
M3 self-tapping screws, 6mm long, cross, round flat head, black plated.
Generally used as a product or label, and then judged to use Sheet Metal or plastic parts.
***Tooth is the number of teeth per ..***
Length conversion
The length of the US standard screw must be converted to the metric mm size.
Conversion formula: (Length Code / 32) x 25.40 = metric length mm
B-3, B-4, B-5: The marking method is the same as the metric system.
Inch screw
C-1: Thread Code:
The mark will be the denominator of 8, and then directly called the number of the molecule.
Ex: 1/8 x 0.50 –PPB: 1 split screw x 0.50” long, PPB
Ex: 5/16 x 0.50 –PPB = 2.5/8 x 0.50-PPB : 2 points half-screw x 0.50” long, PPB
Ex: 5/32 x 0.50 –PPB =1.25/8 x 0.50-PPB: 1 minute 2 PCT half screw x 0.50” long, PPB
Ex: 1/4 x 0.50-PPB= 2/8 x 0.50-PPB: 2 teeth screw x 0.50” long, PPB
Note: Sometimes it will mark coarse or fine teeth.
UNF: Fine teeth: The electronics industry is more common.
UNC: Coarse teeth: Heavy mechanical structures are more common.
Ex: 3/8 x 0.50, UNF – PPB: 3 points fine screw x 0.50” long, PPB.
C-2: Length Code:
For inches, multiply by 25.40 to mm.
With the buckle gauge, the metric is a metric thread, and the inch thread is an inch thread.
It is also possible to use a caliper to measure the outer diameter of the thread, and the pitch.
The outer diameter of the metric thread is in millimeters, such as 6, 8, 10, 12, 18, 20 mm, etc. The pitch is also in millimeters, such as 0.5, 0.75, 1, 1.5, 2, 3, etc.
The outer diameter of the inch thread is in inches, (25.4 mm per inch) such as 3/16, 5/8, 1/4, 1/2, etc. So the metric caliper is often read with irregular decimals. .
Inch pitch is expressed in terms of how many teeth per inch. Set the caliper to 25.4 mm, align one apex with the thread tip, and the other cusp such as the thread cusp is an inch thread. For example, the tangential thread tip should be a metric thread.
When measuring the pitch, it is best to reverse the tip of the thread on the white chalk. The print on the chalk is clear and easy to measure. Measuring the metric pitch should measure a length, such as 10, 15, 20, mm, etc., count the number of teeth, calculate the pitch
Inch units are specified in inch sizes for thread sizes, eg G1". Metric threads are specified in metric units. For example: M30.
The inch is determined by how many teeth are in one inch (2.54 cm), usually 55 degrees. The metric is the pitch of the two cusps, which is the pitch of the MM, usually 60 degrees.
Foot screw: A screw used to fasten the machine to the ground. Also called anchor bolts.
The difference between the inch screw and the American system is difficult to distinguish by visual inspection. The difference between the British and American screws is that the angle of the inch screw is 55 degrees, while the angle of the American screw is 60 degrees. These two standard screws are mostly It can be used universally, but the 1/2 size screw is not available, because the standard thread of the inch 1/2 is 1/2-12 teeth, and the US system is 1/2-13 teeth.



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