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Machine Drawing
MEC-354
Shankar Sehgal
UIET, Panjab University, Chandigarh
Standard Abbreviations
Standard Abbreviations
Standard Abbreviations
Standard Abbreviations
Tolerances and Fits
Tolerances and Fits
Tolerances and Fits
Tolerances and Fits
Tolerances and Fits
Tolerancing individual dimensions
Tolerancing individual dimensions
Tolerancing individual dimensions
Tolerancing individual dimensions
Tolerancing individual dimensions
Fits
Fits
Fits
Fits
Fits
Fits
Shaft basis system
Hole basis system
Machining symbols
Machining symbol
Any machining method may be used
Machining symbol
Circle means: Material removal not permitted
Machining symbol
Bar means:
Material removal by machining is required
Machining symbol
Milled
Any special machining characteristics are mentioned
on the extra horizontal line
Surface finish
Reference profile
Peak-to-valley height
Actual profile
Datum profile
Mean profile
Surface finish parameters
• Actual profile:
– It is the profile of the actual surface obtained by
finishing operation
• Reference profile:
– It is the profile to which the irregularities of the
surface are referred to. It passes through the
highest point of the actual profile.
Surface finish parameters
• Datum profile:
– It is the profile, parallel to the reference profile. It
passes through the lowest point B of the actual
profile.
• Mean profile:
– It is that profile, within the sampling length
chosen (L), such that the sum of the material filled
areas enclosed above it by the actual profile is
equal to the sum of the material-void areas
enclosed below it by the profile.
Surface finish parameters
• Peak-to-valley height:
– It is the distance from the datum profile to the
reference profile.
• Mean roughness index:
– It is the arithmetic mean of the absolute values of
the heights hi between the actual and mean
profiles. It is given by,
Surface roughness number
Surface finish symbols
Measurement of surface finish
1. Straight edge
2. Surface guage
3. Optical flat
4. Tool maker’s microscope
5. Profilometer
6. Profilograph
7. Talysurf
Surface finish symbols
Surface finish symbols
Surface finish symbols
Welding symbols
Elementary welding symbols
Elementary welding symbols
Elementary welding symbols
Supplementary welding symbols
Combination of elementary and
supplementary welding symbols
Welding symbols
Indication of edge preparation
Dotted line is on LOWER side.
This means that LOWER plate is to be prepared
Welding symbol on continuous line (and not on
dotted line).
This means that weld is to be made on arrow side
(and not on the other side).
Weld dimensions
a = throat thickness
z = leg length
Welding process designations
Screw threads
Screw threads
Screw threads
Forms of screw threads
Metric screw thread
Forms of screw threads
Metric screw thread
Forms of screw threads
Forms of screw threads
Forms of screw threads
Forms of screw threads
Forms of screw threads
Forms of screw threads
Thread designation
• M 10 x 1.25 means
– Metric thread of nominal diameter 10 mm and pitch 1.25 mm
(Fine series)
• M 10 means
– Metric thread of nominal diameter 10 mm and pitch 1.5 mm
(Coarse series)
• SQ 40 x 10 means
– SQuare thread of nominal diameter 40 mm and pitch 10 mm
• ACME 40 x 8 means
– ACME thread of nominal diameter 40 mm and pitch 8 mm
• WORM 40 x 10 means
– WORM thread of nominal diameter 40 mm and pitch 10 mm
Left hand thread
Side mirror of Activa scooter
Right hand thread
Conventional representation
of threads
• Crests of threads are indicated by a continuous thick
line and the roots, by a continuous thin line.
• For hidden screw threads, the crests and roots are
indicated by dotted lin
• For threaded parts in section, hatching should be
extended to the line defining the crest of the thread.
• In the view from side, the threaded roots are
represented by a
• portion of a circle, drawn with a continuous thin line,
of length approximately three-quarters of the
circumference.
Conventional representation
of threads
• The limit of useful length of screw threads is
represented by a continuous thick line or a
dotted line, depending on its visibility. The
length up to which the incomplete threads are
formed beyond the useful limit, is known as a
run-out. It is represented by two inclined
lines.
Conventional representation
of threads
Conventional representation
of threads
Schematic representation
of threaded parts - V-threads
Schematic representation
of threaded parts - Square-threads
Bolted joint
Hexagonal nut
Hexagonal nut
Hexagonal nut
Hexagonal nut
Method of drawing hexagonal nut
1. Draw the top view by drawing a circle of diameter, W and describe a regular
hexagon on it, by keeping any two parallel sides of the hexagon, horizontal.
2. Project the view from the front, and the view from side, and mark the height equal
to D.
3. With radius R, draw the chamfer arc 2-1-3 passing through the point 1 in the front
face.
4. Mark points 4 and 5, lying in-line with 2 and 3.
5. Locate points 8,9 on the top surface, by projecting from the view from above.
6. Draw the chamfers 4–8 and 5–9.
7. Locate points 6 and 7, lying at the middle of the outer two faces.
8. Draw circular arcs passing through the points 4, 6, 2 and 3, 7, 5, after determining
the radius R1 geometrically.
9. Project the view from the side and locate points 10, 11 and 12.
10. Mark points 13 and 14, lying at the middle of the two faces (view from the side).
11. Draw circular arcs passing through the points 10, 13, 11 and 11, 14, 12, after
determining the radius R2 geometrically.
Hexagonal headed bolt
Hexagonal headed bolt
with nut and washer
Square nut
Square nut
Square nut
Square headed bolt
Stud bolt or stud
Nuts
Screws
Lock nut
Lock nut
Locking by split pin
Locking by castle nut
Wile’s lock nut
Locking by set screw
Pipe fittings
Pipe fittings
Cotter Joint
Cotter Joint
Knuckle Joint
Knuckle Joint
Muff coupling
Muff coupling
Flange coupling
Flange coupling
Footstep bearing
Front view of footstep bearing
Top view of footstep bearing
Footstep
bearing
Footstep bearing
Footstep bearing
Plummer block
Front view of plummer block
Top view of plummer block
Plummer block
Screw jack
Screw jack
I.C. engine
piston
I.C. engine connecting rod
I.C. engine connecting rod
Lathe tail stock