Page 32 - CITS - ED - Mechanical

ENGINEERING DRAWING - CITS

Helix

Helix (Fig 1): When a point moves at a constant speed along a line which revolve at a constant rate around a fixed
axis. The point traces a curve similar to the coil of a spring, such a curve is called the helix.
The fixed distance through which the point moves parallel to the axis for each revolution of the line is called the
"Pitch" of the helix. (or lead)
The helix is called as cylindrical helix when the revolving line is parallel to the axis of revolution.
If the revolving line is inclined to the axis of revolution the resulting helix is called conical helix. (Fig 2)
The helix may be either right handed or left handed. The right handed helix climbs from the base towards right
side as it rises along the axis.
Practical application: Threads on bolts, screws, nuts, springs, spiral staircase etc.

Fig 1 Fig 2

Helix

Procedure

Exercise 2.14

Construct a helix for two revolutions of a point on a cylinder dia 40 and pitch of helix 30 mm. (Fig 3)

Fig 3

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CITS :Engineering Drawing (Mechanical) - Exercise 2