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All About The Screw Size

The most common screw thread form is one with a symmetrical V-profile. The angle should be 60 degrees. The fundamental operation in manufacture is the creation of shape - this includes assembly, where a number of components are fastened or joined together either permanently by welding for example or detachably by screws, nuts and bolts and so on. There are such a variety of shapes in engineering to be assembled; it is hardly surprising that there is more variety in demountable fasteners than in any other machine element. Fasteners based upon screw threads are the most common so the limitations of the fastened assemblies are appreciated.

Screw comes with many different styles of heads; the three most are flat, round, pan:

1. Flat: These are probably the most common, they are countersunk so they don't protrude above the surfaces so it can be filled and painted over to become invisible. This type of head is used in butt hinges.
2. Round: these are used when countersunk is not required.
3. Pan: These are similar to round head except the top is flat.

Sizes:

There is a number of varieties of shapes in engineering to be assembled; it is hardly surprising that there is more variety in demountable fasteners than in any other machine element. Fasteners based upon screw threads are so common so that the limitations of the fastened assemblies are appreciated. Screw ranging in size from 2.7mm to 7.3 mm. The drivers are differentiated by the colours of their handles. Green, red and black are the three most popular. Screw sizes are listed with the shank size than the length. Shank size are denoted with #'s, larger the number the larger the shank. The most common sizes are 6, 8, and 10 so the medium size screw is 1/1'' 2'' inches. The length of the center portion shall be equal to the screw length minus two screw diameters (2D). The starting thread shall be chambered and the junction between diameters shall be rounded to a value equal to F maximum.