In a triple start thread, which of the following is true?

[L = Lead, P = Pitch]

Explanation:

Lead (L)

It is the distance a screw thread advances axially in one complete revolution.

Pitch (P)

It is the distance from a given point on one thread to a similar point on a thread next to it, measured parallel to the axis of the cylinder.

Important points regarding threads

• Threads are formed on screws in a helix.
• Helix is the path of a point travelling around an imaginary cylinder such that its axial and circumferential velocities maintain a constant ratio. 
• When a single helix is making a screw, it is called a SINGLE START thread. In a single start thread, the LEAD and PITCH are the same. 

• In the case of TWO START (DOUBLE START) threads, one thread is wound within the other exactly in the middle. This enables the lead of the helix increased without increasing the pitch. 
• Lead = Pitch x Number of starts 

• A screw-thread may have any number of starts. The general term for such threads other than single start is MULTI- START.

​∴ For 3 start thread, Lead = 3 × Pitch

Uses of Multiple Threads:

Multiple threads are used wherever quick motion is required and application of great force is not allowed e.g. on fountain pens, bottles, tooth-paste caps, valves, etc. to impart quick action in opening and closing.