Joining

Question 1

Define joining (simple).

Answer 1

Creating a permanent or temporary connection between parts using mechanical fasteners, welding/brazing/soldering, adhesives, or plastic/wood joining methods.

Question 2

Permanent vs temporary joining—difference.

Answer 2

Permanent cannot be separated without damaging the parts (welds, rivets, brazed/adhesive bonds); temporary can be disassembled (bolts/screws).

Question 3

Five common joining families (overview).

Answer 3

Mechanical fasteners; welding; brazing/soldering; adhesive bonding; plastics/wood joining methods.

Question 4

Bolts vs screws—simple difference.

Answer 4

Bolts are used with a nut to clamp parts; screws usually form/engage threads in a tapped hole or the material itself.

Question 5

Why use washers?

Answer 5

Spread load, protect the surface, and reduce loosening or embedment.

Question 6

Two anti‑loosening methods for fasteners.

Answer 6

Nyloc (nylon insert) nuts/spring washers and chemical threadlockers (e.g., medium strength).

Question 7

What is torque and why does it matter?

Answer 7

The tightening moment that creates bolt preload; correct torque helps prevent loosening and joint slip.

Question 8

Riveting—two types at school level.

Answer 8

Blind (pop) rivets installed from one side, and solid rivets set with hammer/dolly or press.

Question 9

Blind rivet selection—two notes.

Answer 9

Match material to joint (e.g., aluminium rivet for aluminium); choose correct grip range for total sheet thickness.

Question 10

What is welding?

Answer 10

Local melting/coalescence of metals (and sometimes filler) to produce a permanent joint.

Question 11

Name four welding processes (school/intro).

Answer 11

MIG/MAG (GMAW), TIG (GTAW), MMA/stick (SMAW), and resistance spot welding.

Question 12

Shielding gas—purpose (MIG/TIG).

Answer 12

Protects the molten pool from oxygen/nitrogen to reduce porosity and oxidation.

Question 13

Heat‑affected zone (HAZ)—what is it?

Answer 13

The region next to the weld that is heated but not melted; properties can change (e.g., hardness).

Question 14

Fillet vs butt weld—difference.

Answer 14

Fillet weld joins parts at an angle (lap/T/corner); butt weld joins edges in the same plane.

Question 15

Three essential PPE items for arc welding.

Answer 15

Welding helmet with suitable shade, gloves/gauntlets, and flame‑resistant clothing/apron.

Question 16

Brazing—simple definition.

Answer 16

Joining using a filler metal that melts above ~450 °C but below the base metals; relies on capillary action.

Question 17

Soldering—simple definition.

Answer 17

Low‑temperature joining (typically <450 °C) using soft solders, common in electronics and light sheet metal.

Question 18

Joint clearance for capillary flow—why important?

Answer 18

Small, even gaps allow the molten filler to wick through the joint for strength and sealing.

Question 19

Flux—purpose in brazing/soldering.

Answer 19

Cleans and protects surfaces from oxidation so filler wets the joint.

Question 20

Why choose adhesives?

Answer 20

Spread loads over a large area, join dissimilar materials, and avoid heat distortion or HAZ.

Question 21

Two key steps in surface preparation for adhesives.

Answer 21

Degrease/clean and abrade/roughen the bonding area; then wipe dust and dry before applying adhesive.

Question 22

Give examples of structural and non‑structural adhesives.

Answer 22

Structural: epoxies, acrylics (MMA), PU; Non‑structural: hot‑melt, PVA (wood), cyanoacrylate for small parts.

Question 23

Clamping/fixturing during cure—why?

Answer 23

Maintains alignment and bond‑line thickness; improves final strength and reduces voids.

Question 24

Adhesive joint design—two tips.

Answer 24

Use lap/strap joints to load in shear; avoid peel by adding flanges, larger overlap, or fillets at edges.

Question 25

Two ways to join thermoplastics.

Answer 25

Solvent welding (e.g., acrylic using solvent cement) and thermal methods (hot‑plate, ultrasonic, heat staking).

Question 26

Solvent welding—simple idea.

Answer 26

A solvent softens surfaces so polymer chains diffuse; as solvent evaporates the joint re‑hardens.

Question 27

Common wood joining methods (school).

Answer 27

PVA wood glue with cramps, screws with pilot/clearance holes, and dowel joints with jigs.

Question 28

Name five joint geometries used across methods.

Answer 28

Lap, butt, T‑joint, corner joint, and scarf/step joints (for adhesives/wood).

Question 29

What to include on a drawing for a welded joint (intro).

Answer 29

Weld type/size/symbol, length/spacing if intermittent, material, and any notes on process or finish.

Question 30

Dissimilar metals—what to watch for?

Answer 30

Galvanic corrosion; insulate or use compatible materials/fasteners and seal joints where moisture can collect.

Question 31

Fastener materials—two guidelines.

Answer 31

Match fastener material/coating to environment (e.g., stainless outdoors) and avoid mixing that causes galvanic pairs.

Question 32

Simple weld inspection—three visible defects.

Answer 32

Porosity (pits), lack of fusion, and undercut/overlap at the toe of the weld.

Question 33

How to check a blind rivet joint quickly.

Answer 33

Confirm correct mandrel head is present, rivet sits tight with no gap, and the grip range was correct.

Question 34

Adhesive bond quality—two quick checks.

Answer 34

Squeeze‑out bead even along the joint and no movement after cure; perform a simple lap‑shear test coupon if critical.

Question 35

Torque check—why after assembly?

Answer 35

Verifies bolt preload has been achieved and detects relaxation or assembly errors.

Question 36

Two fume/extraction notes for joining.

Answer 36

Use LEV for welding fumes and ensure ventilation when using solvent cements/adhesives or solder fluxes.

Question 37

Hot‑work safety—two controls.

Answer 37

Clear combustibles and have fire watch/extinguisher; obtain a hot‑work permit if required on site.

Question 38

Scenario: join two 1.5 mm steel sheets quickly on a car panel.

Answer 38

Use resistance spot welding or blind rivets/adhesive depending on access and equipment.

Question 39

Scenario: aluminium box section to plate, visible finish needed.

Answer 39

TIG weld for clean control, or structural adhesive with prepared surfaces to avoid heat distortion.

Question 40

Scenario: acrylic display parts, clear joint lines desired.

Answer 40

Solvent‑bond with capillary cement on clean, square edges; clamp lightly until fully set.

Question 41

Scenario: wood frame in a class project.

Answer 41

PVA glue with screws/dowels; allow full clamp time and clean squeeze‑out for a neat finish.

Question 42

Lean link—how can joining cut wastes?

Answer 42

Standard torque charts/jigs reduce Defects and Waiting; selecting no‑heat methods can cut rework and Overprocessing.

Question 43

First‑article approach for joining—what is it?

Answer 43

Make one sample joint to verify fit, process settings, and strength before committing to the full batch.