Shared on 16th Nov24 Sheet Metal work & Bench Work Fitting

UNIT-5: SHEET METAL WORK

Introduction

  • Importance of Sheet Metal Work: Essential in engineering concerns for processing metal sheets, requiring knowledge of projective geometry for laying out patterns and cutting accurately.

  • Applications: Utilized in various engineering processes and products.

Tools and Equipment in Sheet Metal Work

Measuring Tools

  • Rules: Variety of lengths for measuring and layout.

  • Folding Rule: Useful for large measurements; should be placed on its edge for accuracy.

  • Steel Square: L-shaped with graduations, consisting of a tongue (narrow arm) and body (wide part).

  • Straight Edge: A flat bar to draw long lines, available in lengths from 1m to 3m.

  • Scratch Awls/Scribers: Tools for marking lines on metal; types include ring scratch awl, socket scratch awl, shank type scratch awl.

  • Dividers: Tapered legs for measuring; includes spring and wing types.

  • Trammel Points: Used to draw large arcs; features two straight legs attached to holders with a pencil clamp.

  • Punches: Types include:

    • Prick Punch: For small indentations (30° point).

    • Centre Punch: For marking bend lines and drilling centers (90° point).

    • Solid Punch: For small holes in thin sheets.

    • Hollow Punch: For larger holes (up to 10mm).

Cutting Tools

  • Chisels: Used for cutting; types include flat chisel, cross-cut chisel, half-round chisel, diamond-point chisel, side chisel.

  • Snips: Heavy-duty scissors for straight/circular cuts; types include straight snips and curved snips.

Hammers

  • Types of Hammers: Each serves distinct functions in metalwork:

    • Ball Peen Hammer: General-purpose with a round face.

    • Riveting Hammer: Square face for spreading rivets.

    • Setting Hammer: Flat face for flattening seams.

    • Hollowing/Blocking Hammer: For hollow shapes.

    • Raising Hammer: For raising circular discs.

    • Planishing Hammer: For work on domed shapes.

    • Mallets: For softer blows to avoid metal damage.

Pliers

  • Types of Pliers: Used for holding, cutting, and bending:

    • Flat Nose Pliers: For attaching work.

    • Round Nose Pliers: For shaping and forming patterns.

Bench Stakes

  • Use of Bench Stakes: Steel anvils for operations like bending and forming:

    • Blow Horn Stakes: Tapered for forming and riveting.

    • Hatchet Stake: For holding sharp bends.

    • Half Moon Stake: For circular folds.

    • Creasing Stake: Grooved for sinking beads and making tubes.

Sheet Metal Operations

Categories of Operations

  • Cutting Operations: Stress metal beyond ultimate strength (e.g., blanking, cutting).

  • Forming Operations: Stress below ultimate strength, involving no material removal (e.g., bending, drawing).

Common Cutting Operations

  1. Blanking: Cutting out shapes; the punched-out part becomes the blank.

  2. Punching (Piercing): Producing holes, with removed material as waste.

  3. Notching: Cutting from edges without cutting full surface.

  4. Perforating: Creating multiple small holes close together.

  5. Slitting: Unfinished cuts through limited lengths.

  6. Lancing: Cutting and bending small portions downwards.

  7. Shearing: Straight cuts across metal sheets using specified stages (plastic deformation, fracture).

Common Forming Operations

  1. Bending: Transforming shapes (U-bending, V-bending, edge bending).

  2. Drawing: Shaping sheets into cups using pressure.

  3. Embossing: Creating design features for decoration or identification.

  4. Forming: Shaping metal into specified forms without flow.

  5. Coining (Squeezing): Filling dies with metal using compressive pressure.

Safety Precautions in Fitting Shop

  • Maintain cleanliness to prevent accidents.

  • Use appropriate protective gear and tools.

  • Follow guidelines for safe handling of machines and tools.

Measuring and Marking Tools

Important Tools

  • Steel Ruler: For direct measuring, various lengths available.

  • Calipers: For gauging dimensions:

    • Outside Caliper: Measures outer dimensions.

    • Inside Caliper: Measures inner dimensions.

  • Try Square: For marking right-angles and ensuring flatness.

  • Scriber: Marks lines on metals.

  • Universal Surface Gauge: For scribing lines at specific heights.

  • Punches: Essential for marking and locating drill points.

  • V-blocks: For holding round bars during machining.

Tools Overview

  • Files: Hardened steel with tooth rows; classified by size, shape, grade, and cut.

  • Hacksaws: For sawing metals; types include solid frame and adjustable frame.

  • Hammers: Varying types for different tasks (e.g., ball peen, straight peen).

  • Vices: Commonly used for holding work securely.

  • Surface Plates: For marking, ensure flatness in surface work.