Introduction to Basic Manufacturing Processes and ... - always yours

358 Introduction to Basic Manufacturing Processes and Workshop Technology
5. Dovetail seam
It is used to join a flat plate to a cylindrical piece. To layout such a seam, draw a line
parallel to one edge of sheet metal component at a distance of 6 to 20 mm. depending upon
the size of the hole of sheet metal part. Then draw lines to indicate where the sheet metal
part is to be slit. The width of the piece between slits ranges from 6 to 26 mm.
6. Flanged or burred bottom seam
It is used to fasten the bottom of a container made of sheet metal to its body in which
upper part is the sheet metal body and lower bottom of a container. To layout such a seam
on sheet metal part, draw a circle, which represents the outline of the bottom on sheet metal
part. If it is square or rectangular component, draw the bottom shape on the sheet metal part.
Then draw a second line to show the width of the flange. The width of this flange may range
from 3 to 6 mm on sheet metal part.
18.4.3 Notches
In the process of laying out on sheet metal part, some provision is to be made for bent
sections when they have folded edges. The opening left at corners of seams and edges of sheet
metal part are called notches. Five common types of notches are: (1) Straight notch, (2) V-
notch, (3) Square notch and (4) Slant notch.
1. Straight notch. It is prepared by making a straight cut where the bend is to occur
in sheet metal part.
2. V-notch. It is used where the corners of a flange
should fit together in sheet metal part. It is used for
laying out 90° and other than 90° angle on the sheet
Lap
metal part
3. Square notch. It is applicable where square or
rectangular box (made up of sheet metal) is formed.
Seam
4. Slant notch. It is used where single hems are to
meet at right angles. In this process they should be
clipped at 45° angle on the sheet metal part.
Locked seam
Hem
18.4.4 Folded Sheet Metal Joints
Wired edge
As per requirements, various types of sheet metal joints
are used in sheet metal work. Such joints are commonly
Cup or
used to fasten bottoms to cylinders, square or rectangular
circular
containers. Some of the commonly used such joints are shown
in Fig. 18.11.
1. Lap joint. It is very frequently used in sheet metal
work and can be prepared by means of soldering or
Flanged
riveting.
2. Seam joint. This joint is a very generally used in
Cap
sheet metal work. It is locked, as shown in the
Fig. 18.11 Various sheet
diagram, so as to ensure a positive grip and also to
metal joints
make the joint flush with the surface.
3. Locked seam joint. This joint is used for locking seam joints in sheet metal work.