Machine Drawing

Screwed Fasteners 93

dharm
d:\N-Design\Des5-1.pm5 Seventh Print

2D

0.6 D

L DD DD

0.6 D 0.2 D

90°

0.2 D

L

Hexagonal head Flat head

0.6 D 0.4 D

0.2 D

L DD

Round head

DD

1.5 D

0.2 D

0.6 D

L

Cheese head

DD

Oval head

0.6 D

L

R = 2.25 D 0.2 D

90°

0.4 D DD

DL

0.75 D

1.5 D

30°

Socket head

Fig. 5.24 Types of machine and cap screws

Cap screws are produced in finish form and are used on machines where accuracy and

appearance are important. As cap screws are inferior to studs, they are used only on machines

requiring few adjustments and are not suitable where frequent removal is necessary. These are

produced in different diameters, upto a maximum of 100 mm and lengths 250 mm.

Machine screws are produced with a naturally bright finish and are not heat treated. They

are particularly adopted for screwing into thin materials and the smaller ones are threaded

throughout the length. They are used in fire-arms, jigs, fixture and dies. They are produced in

different diameters upto a maximum of 20 mm and lengths upto 50 mm.

5.9.8 Set Screws

These are used to prevent relative motion between two

rotating parts, such as the movement of pulley on shaft.

For this, a set screw is screwed into the pulley hub so

that its end-point bears firmly against the shaft (Fig. 5.25).

The fastening action is by friction between the screw and

the shaft.

Set screws are not efficient and so are used only

for transmitting very light loads. For longer life, set

screws are made of steel and case hardened. Further,

for better results, the shaft surface is suitably machined

for providing more grip, eliminating any slipping

tendency. Figure 5.26 shows different forms of set

screws.

Fig. 5.25

0.25 D

D L