Assembly Drawings 303
dharm
d:\N-Design\Des18-2.pm5
The isometric view of a four jaw chuck is shown in Fig. 18.27a. It consists of a cast iron
body 1, in which is located the screws 3 and the jaws 2 which engage with each other with square
threads. The screws are held in position by the locators 4 which prevent their axial movement as
well. When the screws are operated by means of a chuck key (not shown), the jaws move towards
or away from the centre. Thus, the four jaws can be moved independently to grip the job firmly.
The locators are fixed to the body by means of screws 5. The body of the chuck is fixed to the back
plate by means of four M 18 bolts. The details of the chuck are illustrated in Fig. 18.27b.
3
2
4
1
Fig. 18.27a Four jaw chuck
Exercise
The details of a four aw chuck are shown in Fig. 18.27b. Assemble the parts and draw, (i) the view
from the front, as seen from the side of the jaws and (ii) the half sectional view from left.
Also consider suitable local section for showing other details.
18.4 Valves and Boiler Mountings
18.4.1 Gate Valve
A valve is used on a fluid line to check or control the fluid flow. It may be operated by the pressure
of the fluid or by hand. A number of designs of valves are available; however the gate valve
permits the whole area of the passage for the flow of fluid, when fully opened. This minimizes any
energy loss in the fluid flow.
Figure 18.28 shows the details of a gate valve. The wedge valve 4 in this design is guided by
the control screw 5. When fully opened, the wedge valve clears-off the passage in the valve body 1
for the flow of fluid. The inside union 8 is slipped onto the stem from below. This is placed in the
union 2 and screwed. The wedge valve is threaded on the stem and the assembly is placed in the
valve body and screwed. The gland is placed from the top of the stem so that it enters the union.
It is fixed in position by the union ring 3. Finally, the hand wheel 6 is placed on the square end of
the screw and fixed in position by means of a nut (not shown). The gate valve may be fixed for any
direction of the fluid flow.
