Slide 2:
Major diameter: It is the largest diameter of External or Internal Thread. The screws are generally specified by this diameter. It is also known as nominal or outside diameter. Minor diameter: It is the smallest diameter of External or Internal Thread. It is also known as core or root diameter. Pitch diameter: It is the mean or effective diameter which is same for External and Internal threads. Pitch It is distance from a point on one thread to the corresponding point on next thread. In metric system pitch are express in mm. In Whitworth system thread are generally express as no. of thread per inch. General definition of Thread
Slide 3:
Forms of Screw Threads There are various standards have been adopted to make the Screw thread. The most common standards are:.
1. British Standard Whitworth (BSW) threads.
2. ISO Metric Screw threads
The screws are generally classified on the basis of shape of the thread profile, the most common are:
1. V-shape thread
2. Square thread
3. Trapezoidal thread
4. Saw tooth thread
Threads are also classified as single start or multiple start threads. Right hand or Left hand threads etc. Threads are also classified as single start or multiple start threads. Right hand or Left hand threads etc. Lead It is distance which a screw thread moves axially in on rotation.
Lead = Pitch (for single start thread)
Lead = 2*Pitch (for double start thread)
Lead = 3*Pitch (for triple start thread) and so on …...
Slide 4:
P = Pitch (mm)
D = Major dia. of Internal thread (Nut) (mm)
D1 = Minor dia. of Internal thread (Nut) (mm)
D2 = Pitch dia. of Internal thread (Nut) (mm)
d = Major dia. of external thread (Bolt) (mm)
d2 = Pitch dia. of external thread (Bolt) (mm)
d3 = Minor dia. of external thread (Bolt) (mm)
H = Height of fundamental triangle (mm)
H1 = Maximum depth of engagement (mm)
h3 = Basic depth of external thread (mm)
As = Stressed Area (mm2) Metric ISO Threads Design Profile of External and Internal thread Symbols: D1 = d – 2 H1
d2 = D2 = d – 0.64953 P
d3 = d – 1.22687 P
H = 0.86603 P
H1 = 0.54127 P
h3 = 0.61343 P
R = 0.14434 P Center line of Nut / Bolt Bolt size designation
Slide 5:
Bearing depth, H1 = 0.5 P
Pitch dia., d2= D2 = d – H1
A3 = Core Area Core dia, d3 = d -2 h1
h1= 0.5 p
A3 = Core Area Property class for Bolt
Slide 6:
1. Force on the Pitch circle P= Pitch
F1 = Effort / Hand force
F2 = Load / Weight
r2 = Pitch circle radius
d2 = Pitch circle diameter Work done = Force * Distance Work Input = Effort * Distance moved by effort
= F1 * 2*p*r2 Work Output = Load * Distance moved by Load
= F2 * P Considering one revolution of a Screw Converting Torque into axial Force
Slide 7:
2. Force on lever periphery P= Pitch
F1 = Effort / Hand force
F2 = Load / Weight
R = Radial distance of effort from center Work done = Force * Distance Considering one revolution of a Screw Work Input = Effort * Distance moved by effort
= F1 * 2*p*R Work Output = Load * Distance moved by Load
= F2 * P