Threads Flashcards
Minor Diameter
Smallest diameter on a straight external or internal thread
Pitch diameter
Diameter of imaginary cylinder which passes through thread at points where width of the groove and width of thread are equal
Side or flank
Surface which connects the two sides of a thread crest with the root
Crest
Top surface of an external thread
Root
Bottom surface of a thread
Thread Angle
Angle between the sides of a screw thread
Pitch
Distance from a point one on screw thread to corresponding point on an adjacent thread.
Lead
Distance a screw thread advances in one revolution
Thread depth
Measurement between crest and root
Single, double, triple pitch leads
Multiple threads used when it is required to increase the lead.
Double start the lead is twice the pitch
Triple the lead is triple the pitch.
Areas a double or triple used in power plant
Unwavering valves, backfill valves
Types of threads
- American Standard
- Whitworth Standard
- Square Thread
- Acme
- V type
What is the American Standard
The thread has a 60* angle with a root and crest 1/8 the pitch
Sharp V thread
Same as United standard but the root and crest come to a point
Whitworth standard thread
Has a 55* angle with rounded crest and roots
