Bearings

Given Information:
- Assembly: Open Bearing
- Parts: Body (Cast Iron) – 1 off, Bush (Gun Metal) – 1 off
- All fillets and rounds = R5
- Scale: 1:1
- Projection: First Angle

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Step 1 – Understand the Parts

Body (C.I.):
- A rectangular base/pedestal with a semi-circular (open-top) seating at the top centre to receive the bush.
- The base has bolt holes for fixing to a surface.
- Typical overall dimensions (read from detail drawing): Base length ≈ 100 mm, Base width ≈ 60 mm, Height ≈ 60 mm, Bore (semi-circular seat) diameter ≈ 50 mm.

Bush (G.M.):
- A half-cylindrical (semi-circular) bush that sits in the open seat of the body.
- Outer diameter matches the seat in the body (≈ 50 mm), Inner diameter (bore) ≈ 25 mm.
- The bush is a plain half-bush (open bearing type — no cap).

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Step 2 – Assembly Principle

The Gun Metal bush is placed into the semi-circular recess of the Cast Iron body. The shaft rests on the inner bore of the bush. Since it is an OPEN bearing (no top cap), the bush simply sits in the body's open seat.

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Step 3 – Drawing Procedure

(a) Front View – Left Half in Section:

1. Draw the outer profile of the assembled bearing in the front view (full external view on the right half).
2. On the LEFT half, draw a sectional view by cutting along the vertical centre plane (plane of symmetry).
3. In section, show:
- The C.I. body: hatch with Cast Iron hatching (evenly spaced 45° lines).
- The G.M. bush seated in the body: hatch with Gun Metal hatching (closer spaced 45° lines, or cross-hatching as per convention).
- The semi-circular bore of the bush (inner hole) is visible.
4. Show fillets R5 at all internal corners.
5. The base of the body shows the bolt holes (shown as hidden lines on the right half, or in section on the left half).

(b) Left Side View:

1. Project the Left Side View from the Front View.
2. Show the full external profile of the body from the left side.
3. The semi-circular open top of the body is visible.
4. The bush (half-cylinder) is visible sitting in the seat.
5. Show the base plate outline, bolt holes as circles (or hidden lines).
6. All visible edges are drawn as continuous thick lines; hidden edges as dashed lines.

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Step 4 – Six Important Dimensions to be Marked

$$\text{1. Overall length of base} = 100 \text{ mm}$$
$$\text{2. Overall width of base} = 60 \text{ mm}$$
$$\text{3. Overall height of body} = 60 \text{ mm}$$
$$\text{4. Bore diameter of bush (shaft hole)} = \phi\,25 \text{ mm}$$
$$\text{5. Outer diameter of bush / seat diameter} = \phi\,50 \text{ mm}$$
$$\text{6. Bolt hole diameter and pitch} = \phi\,10 \text{ mm, PCD or spacing as given}$$

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Step 5 – Title Block and Projection Symbol

- Title: OPEN BEARING – ASSEMBLY
- Scale: 1:1
- Projection Symbol: First Angle Projection symbol (truncated cone symbol) drawn in the title block.
- Material Notes: Body – C.I., Bush – G.M.

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Key Drawing Conventions:
- Section lines (hatching) at 45°, spaced 3–4 mm apart.
- C.I. hatching: thin lines at 45°.
- G.M. hatching: cross-hatching or closer lines at 45° (differentiated from C.I.).
- Centre lines: thin chain (dash-dot) lines through the bore axis.
- Dimension lines: thin continuous lines with arrowheads.
- All fillets and rounds = R5 (shown as small arcs at corners in section).

Given Information:
- Assembly given: Open Bearing (Fig. 3.7)
- Task: Disassemble and draw detail (part) drawings of Base and Bush separately.
- Scale: 1:1
- Projection: First Angle

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Step 1 – Identify Parts from Assembly

From the Open Bearing assembly:
- Base (Body) – C.I.: Rectangular pedestal with a semi-circular open recess at the top to seat the bush. Has a flat base with bolt holes.
- Bush – G.M.: Half-cylindrical bush (semi-circular cross-section) that fits into the recess of the base.

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Step 2 – Part (a): BASE

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

1. Draw the full front view outline of the Base (body) — a rectangular block with a semi-circular recess at the top centre.
2. On the LEFT half: draw the sectional view along the vertical centre plane.
- In section, show the internal profile: the semi-circular seat, the solid walls of the body, the base thickness.
- Apply C.I. hatching (45° lines, 3–4 mm spacing) to all cut surfaces.
3. On the RIGHT half: show the external view — visible edges of the body, bolt holes (as hidden or visible depending on position), outer profile.
4. Show fillets R5 at all internal corners in section.
5. Draw centre lines through the axis of the semi-circular seat.

(ii) Top View of Base:

1. Project the top view directly below the front view.
2. Show the rectangular base outline.
3. Show the semi-circular recess (open at top) as a visible semi-circle at the centre.
4. Show bolt holes as circles at the four corners (or as per given drawing).
5. Show centre lines.
6. Hidden edges (e.g., underside features) shown as dashed lines.

Six Important Dimensions for Base:
$$\text{1. Overall length} = 100 \text{ mm}$$
$$\text{2. Overall width} = 60 \text{ mm}$$
$$\text{3. Height of body} = 60 \text{ mm}$$
$$\text{4. Diameter of semi-circular seat} = \phi\,50 \text{ mm}$$
$$\text{5. Bolt hole diameter} = \phi\,10 \text{ mm}$$
$$\text{6. Base plate thickness} = 15 \text{ mm (or as given)}$$

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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 half-cylinder (flat face at bottom, curved face at top).
2. On the RIGHT half: draw the sectional view along the vertical centre plane.
- In section, show the inner bore (hollow semi-circle) and the wall thickness of the bush.
- Apply G.M. hatching (cross-hatching or differentiated 45° lines) to cut surfaces.
3. On the LEFT half: show the external view — the curved outer surface and flat bottom face.
4. Draw centre lines through the bore axis.

(ii) Top View of Bush:

1. Project the top view below the front view of the bush.
2. Show the rectangular outline of the bush (length × width of the half-cylinder).
3. Show the inner bore as a rectangle (or semi-circle depending on orientation) with hidden/visible lines.
4. Show centre lines.

Six Important Dimensions for Bush:
$$\text{1. Outer diameter of bush} = \phi\,50 \text{ mm}$$
$$\text{2. Inner bore diameter} = \phi\,25 \text{ mm}$$
$$\text{3. Length of bush} = 60 \text{ mm (or as given)}$$
$$\text{4. Wall thickness} = \frac{50-25}{2} = 12.5 \text{ mm}$$
$$\text{5. Overall height of bush (semi-circle)} = 25 \text{ mm (radius)}$$
$$\text{6. Width of flat face} = 50 \text{ mm}$$

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Step 4 – Title Block and Projection Symbol

- Title (a): BASE – OPEN BEARING, Scale 1:1, Material: C.I.
- Title (b): BUSH – OPEN BEARING, Scale 1:1, Material: G.M.
- Projection Symbol: First Angle Projection symbol in title block of each sheet.

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Key Conventions:
- Sectioned surfaces hatched at 45°; C.I. and G.M. hatching differentiated.
- Centre lines as thin chain lines.
- All fillets R5 shown in section views.
- Dimension lines thin with arrowheads; all dimensions in mm.