4.1 Methods of joining sheet metal

• Types of sheet-metal joints: butt, lap, seam
• Methods of joining: riveting, fasteners, screw threads, seaming, soldering
• Performing a sheet-metal joining process
• Safety in sheet-metal joining

• identify types of sheet-metal joints used in metal technology
• explain the methods used in joining sheet metals
• perform a task using sheet-metal joining methods
• appreciate the use of sheet-metal joining methods in day-to-day life

“Why are sheet-metal joining methods important?”

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1. Why sheet metal has to be joined
   40 min · 1 practice tasks · quiz
   Sheet metal is sold flat, so every article made from it depends on a joint - and the joint is where it fails.
2. What makes a joint a good one
   40 min · 1 practice tasks · quiz
   The four requirements of a sheet-metal joint - strength, tightness, appearance and cost - and how the article decides which matters most.
3. The butt joint
   40 min · 1 practice tasks · quiz
   The simplest joint, why a plain butt has almost no strength in sheet, and how a backing strip makes it usable.
4. The lap joint
   40 min · 1 practice tasks · quiz
   The overlap joint that most sheet-metal work uses, why it is strong, and the one drawback of the step it leaves.
5. The grooved seam
   40 min · 1 practice tasks · quiz
   Folding, hooking, flattening and grooving two edges into a locked seam that needs no rivets or solder.
6. Other seams and where each is used
   40 min · 1 practice tasks · quiz
   The lap, knocked-up and paned-down seams, and why the knocked-up seam is what fastens a bottom into a container.
7. Allowing metal for the seam
   40 min · 1 practice tasks · quiz
   Why a seam consumes metal, how much to add at each edge, and what happens to an article marked out without an allowance.
8. How a rivet holds
   40 min · 1 practice tasks · quiz
   What happens when a rivet is set, why it must be softer than the sheet, and why a riveted joint is permanent.
9. Rivet types and sizes
   40 min · 1 practice tasks · quiz
   Choosing the head shape for the job and working out the right diameter and length of rivet.
10. Setting a rivet
    40 min · 1 practice tasks · quiz
    The four-stage riveting sequence with the rivet set, hammer and snap, and the step that learners skip.
11. Rivet spacing and edge distance
    40 min · 1 practice tasks · quiz
    How far apart rivets should be and how far from the edge, and what goes wrong when either is too small.
12. Pop rivets
    40 min · 1 practice tasks · quiz
    How a blind rivet forms its own far head, where it is the only option, and what it gives up in exchange.
13. Bolts, nuts and screws in sheet
    40 min · 1 practice tasks · quiz
    The one joining method that can be undone, why washers are essential in thin sheet, and when a threaded fastener is the right answer.
14. Self-tapping and machine screws
    40 min · 1 practice tasks · quiz
    Screws that cut their own thread in sheet, when to use them instead of a bolt, and how a machine screw in a tapped hole differs.
15. How soft soldering works
    40 min · 1 practice tasks · quiz
    Solder melting and being drawn into the joint by capillary action, and why it seals well but is weak.
16. Flux and preparing the surfaces
    40 min · 1 practice tasks · quiz
    Why solder will not stick to oxide, what flux does about it, and choosing between active and passive fluxes.
17. Making a soldered joint
    40 min · 1 practice tasks · quiz
    The five steps of soldering a lap joint, and the single mistake that ruins most school soldering.
18. Choosing a joining method
    40 min · 1 practice tasks · quiz
    Two questions that settle most cases, and the combinations that use more than one method on the same article.
19. Safety in sheet-metal joining
    40 min · 1 practice tasks · quiz
    The four hazards of this work - cut edges, heat, flux fumes and flying rivet tails - and the controls for each.
20. A joining task: making a tray
    40 min · 1 practice tasks · quiz
    Bringing every method together on one article - a riveted, soldered, wired and bolted workshop tray.