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Screw

Screw is an inclined plane introduced to a nail. A screw can have partial or full threads.

 Parts of a Screw:
1. Head
Head is the top most part of the screw where the force is applied with the help of screw driver or wrench.

2. Bearing surface
It is the surface below the head which produces an axial force to the substrate.

3. Thread

4. Pitch
Gap between 2 threads is called thread.

5. Shank
The conical area below the head is called Shank.

6. Substrate
The surface which is to be screwed is called sustrate.












 Screws and Bolts:

1. Screws grip on the substrate, while the bold requires a nut to produce an axial grip.
2. The screw has only one bearing surface while bolt and nut combination gives 2 bearing surfaces.
3. Nut and bolt combination consist of both male and female threads, while screw generally has only male threads.

Different Types of Screw heads:

a) pan


b) round (decorations)


c) truss (mushroom, prevent tampering)

e) flat (countersunk)


f) oval (raised head, raised countersunk, decorations)


g) Bugle head (large eye screw)


h) cheese head


i) filister head (raised cheese head)
 H/d of cheese head > H/d of filister head

j) flanged head (increased contact area)

k) dome (button)


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