Bearings — NCERT Solutions

Given Information:

• Assembly: Bush Bearing
• Parts: Body (C.I.) – 1 off, Bush (G.M.) – 1 off (cylindrical bush pressed into the body)
• Scale: 1:1
• Projection: First Angle

Step 1 – Understand the Parts

Body (C.I.) – Bush Bearing:

• A pedestal/block with a CIRCULAR (full cylindrical) hole bored through it horizontally to receive the bush.
• Has a flat base with bolt holes.
• Typical dimensions: Base length ≈ 100 mm, Width ≈ 60 mm, Height ≈ 75 mm, Bore ≈ 50 mm diameter.
• Unlike the Open Bearing, the Bush Bearing has a COMPLETE circular bore (not open at top).

Bush (G.M.):

• A full cylindrical bush (hollow cylinder) pressed into the bore of the body.
• Outer diameter = bore of body ≈ 50 mm; Inner diameter (shaft hole) ≈ 30 mm.
• Length of bush = width of body bore.

Step 2 – Assembly Principle

The G.M. cylindrical bush is pressed (interference fit) into the circular bore of the C.I. body. The shaft runs through the inner bore of the bush. The body is bolted to the machine bed through the base holes.

Step 3 – Drawing Procedure

(a) Front View – Left Half in Section:

1. Draw the full front view outline of the assembled Bush Bearing.
2. On the LEFT half: cut along the vertical centre plane (plane containing the bore axis).

• Show in section:
• C.I. body walls — hatch with C.I. convention (45° lines).
• G.M. bush (cylindrical ring) — hatch with G.M. convention (cross-hatch or differentiated lines).
• Inner bore of bush (shaft hole) — left open (no hatching, it is a void).
• Show the base, pedestal walls, and the circular bore all in section.

3. On the RIGHT half: show the external view — outer profile of body, visible edges of base, bolt holes.
4. Show centre lines: horizontal axis of bore, vertical axis of symmetry.
5. Show fillets and rounds at corners.

(b) Right Side View:

1. Project the Right Side View from the Front View (First Angle Projection — placed to the LEFT of the front view in First Angle, but labelled as Right Side View).

Note: In First Angle Projection, the Right Side View is placed to the LEFT of the Front View.

2. Show the circular bore as a circle (visible) at the centre of the side view.
3. Show the outer profile of the body from the right side.
4. Show the base plate outline and bolt holes (as circles or hidden lines).
5. Show the bush ends as a circle (outer diameter of bush) concentric with the bore circle.
6. All visible edges: thick continuous lines; hidden edges: dashed lines.

Step 4 – Six Important Dimensions

$$\text{1. Overall length of body} = 100 \text{ mm}$$
$$\text{2. Overall height of body} = 75 \text{ mm}$$
$$\text{3. Overall width of body} = 60 \text{ mm}$$
$$\text{4. Inner bore diameter of bush (shaft hole)} = \phi\,30 \text{ mm}$$
$$\text{5. Outer diameter of bush / bore of body} = \phi\,50 \text{ mm}$$
$$\text{6. Bolt hole diameter and spacing} = \phi\,10 \text{ mm}$$

Step 5 – Title Block and Projection Symbol

• Title: BUSH BEARING – ASSEMBLY
• Scale: 1:1
• Projection Symbol: First Angle Projection symbol in title block.
• Material: Body – C.I., Bush – G.M.

Key Drawing Conventions:

• C.I. hatching: 45° lines, 3–4 mm apart.
• G.M. hatching: cross-hatching (two sets of 45° lines) or closer spacing — must be visually different from C.I.
• Centre lines: thin chain (dash-dot) lines.
• The bore axis is a horizontal centre line in the front view and appears as a point (with centre mark) in the side view.
• Dimension lines: thin with arrowheads, all in mm.

Given Information:

• Assembly given: Bush Bearing (Fig. 3.14)
• Task: Disassemble and draw detail (part) drawings of Body and Bush separately.
• Scale: 1:1
• Projection: First Angle
• Position of parts with respect to H.P. and V.P. to remain the same as in assembly.

Step 1 – Identify Parts from Assembly

• Body – C.I.: Pedestal block with a full circular bore running horizontally through it. Flat base with bolt holes.
• Bush – G.M.: Full cylindrical (hollow) bush that was pressed into the body bore.

Step 2 – Part (a): BODY

(i) Front View of Body – Left Half in Section:

1. Draw the full front view outline of the Body.
2. On the LEFT half: section along the vertical centre plane.

• Show in section:
• The solid C.I. walls of the pedestal and base.
• The circular bore (now empty — bush removed) shown as a void (no hatching inside the bore).
• The bore appears as a rectangle in section (two horizontal lines representing top and bottom of the bore).
• Apply C.I. hatching (45° lines, 3–4 mm spacing) to all cut solid material.

3. On the RIGHT half: show the external view — outer profile, base, bolt holes as hidden or visible lines.
4. Show centre lines: horizontal bore axis, vertical axis of symmetry.
5. Show fillets and rounds at corners.

(ii) Side View of Body:

1. Project the Side View from the Front View.
2. Show the circular bore as a full circle (visible) at the centre — this is the most prominent feature.
3. Show the outer rectangular profile of the body from the side.
4. Show the base plate and bolt holes.
5. All visible edges: thick continuous lines; hidden edges: dashed lines.

Six Important Dimensions for Body:
$$\text{1. Overall length} = 100 \text{ mm}$$
$$\text{2. Overall height} = 75 \text{ mm}$$
$$\text{3. Overall width} = 60 \text{ mm}$$
$$\text{4. Bore diameter} = \phi\,50 \text{ mm}$$
$$\text{5. Base plate thickness} = 15 \text{ mm}$$
$$\text{6. Bolt hole diameter} = \phi\,10 \text{ mm}$$

Step 3 – Part (b): BUSH

(i) Front View of Bush – Right Half in Section:

1. Draw the full front view outline of the Bush — a hollow cylinder (appears as a rectangle in front view with two concentric circles visible in side/end view).
2. In front view: the bush appears as a rectangle (length × outer diameter).
3. On the RIGHT half: section along the vertical centre plane.

• Show in section:
• The G.M. wall of the bush (annular cross-section cut).
• Apply G.M. hatching (cross-hatching or differentiated 45° lines) to the cut wall.
• The inner bore (hollow) left open — no hatching.

4. On the LEFT half: show the external view — outer cylindrical surface (appears as rectangle), and the inner bore shown as hidden lines (dashed).
5. Show centre lines: horizontal axis of the cylinder, vertical axis of symmetry.

(ii) Top View of Bush:

1. Project the Top View from the Front View.
2. The bush is a cylinder; its top view (looking from above) shows:

• Outer circle: $\phi\,50$ mm (outer diameter).
• Inner circle: $\phi\,30$ mm (inner bore diameter).
• Both circles are concentric.

3. Show centre lines (two perpendicular centre lines through the centre).
4. The top view clearly shows the annular (ring) cross-section of the bush.

Six Important Dimensions for Bush:
$$\text{1. Outer diameter} = \phi\,50 \text{ mm}$$
$$\text{2. Inner bore diameter} = \phi\,30 \text{ mm}$$
$$\text{3. Length of bush} = 60 \text{ mm (or as given)}$$
$$\text{4. Wall thickness} = \frac{50-30}{2} = 10 \text{ mm}$$
$$\text{5. Chamfer at ends (if any)} = 2 \times 45^\circ$$
$$\text{6. Overall length to outer diameter ratio (for fit specification)}$$

Step 4 – Title Block and Projection Symbol

• Title (a): BODY – BUSH BEARING, Scale 1:1, Material: C.I.
• Title (b): BUSH – BUSH BEARING, Scale 1:1, Material: G.M.
• Projection Symbol: First Angle Projection symbol drawn in the title block of each drawing.

Key Drawing Conventions:

• C.I. hatching: 45° lines, evenly spaced 3–4 mm.
• G.M. hatching: cross-hatching (two sets of parallel lines at 45° to each other) — clearly differentiated from C.I.
• Centre lines: thin chain (dash-dot) lines extending slightly beyond the outline.
• Hidden lines: thin dashed lines.
• Outlines: thick continuous lines.
• All dimensions in mm; dimension lines thin with arrowheads.
• The bore axis of the bush must be kept in the same orientation (horizontal) as in the assembly, as instructed.