---
title: "Temporary and permanent joints; soldering, brazing, welding"
subject: "Workshop Technology"
chapter: 10
key: "semester_2/workshop_technology:joints-soldering-brazing-welding-compare"
source: https://www.bctengineer.com/q/semester_2/workshop_technology/joints-soldering-brazing-welding-compare
site: BCT Engineering
---

# Temporary and permanent joints; soldering, brazing, welding

Workshop Technology · Chapter 10: Metal Joining Process

- Asked in: year not given, 6 marks
- Video: [Basics of Welding and Joining Technologies-Welding VS brazing & soldering](https://www.youtube.com/watch?v=U2cMZChOGPg) — serdabjob
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_2/workshop_technology/joints-soldering-brazing-welding-compare
- Whole chapter: https://www.bctengineer.com/md/semester_2/workshop_technology/chapter-10

## Question

Classify joints as temporary and permanent with examples. Differentiate between soldering, brazing and welding.

## Short answer

Temporary joints (bolts, screws, keys) can be dismantled; permanent joints (rivets, welds, brazes) cannot. Soldering uses filler below 450 °C without melting the base metal; brazing uses filler above 450 °C, base metal unmelted; welding melts the base metal. Solder gives low strength, brazing medium, welding highest.

## Answer

#### Types of joints
- Temporary joints can be taken apart without damaging the parts: bolts and nuts, screws, studs, keys, cotters, pins, couplings.
- Permanent joints cannot be separated without damage: riveting, welding, brazing, soldering, adhesive bonding.

#### Soldering, brazing and welding
| Point | Soldering | Brazing | Welding |
|---|---|---|---|
| Filler melts at | Below 450 °C | Above 450 °C but below the melting point of the base metal | The base metal itself melts and fuses (filler, if used, is of similar composition) |
| Filler | Tin-lead solder | Brass (Cu-Zn) or silver alloys | Same as or similar to the parent metal |
| Heat source | Soldering iron, torch | Torch, furnace | Gas flame, electric arc, resistance |
| Joint strength | Low | Medium to high | Highest, close to the parent metal |
| Parent metal | Not melted | Not melted | Melted |
| Flux | Rosin, zinc chloride | Borax | Not always; flux coating or shielding gas |
| Use | Electronics, tin cans, plumbing | Tool tips, bicycle frames, pipes | Structures, vessels, pipes, machinery |

Brazing works by capillary action, like soldering, with a gap of 0.05 to 0.25 mm. It can join different metals (steel to cast iron or copper) and uses less heat, so it causes less distortion than welding.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. Which list contains only temporary joints?
   A. Rivets, welds, bolts
   B. Bolts, screws, keys, cotters
   C. Brazing, soldering, pins
   D. Adhesive bonds, studs, couplings
   Answer: B. Temporary joints can be dismantled without damage; rivets, welds, brazing, soldering and adhesives are permanent. (Key point: Temporary vs permanent joints)

2. How do soldering and brazing differ in terms of filler melting point?
   A. Soldering filler melts above 450 °C; brazing below 450 °C
   B. Both melt below 450 °C
   C. Soldering filler melts below 450 °C; brazing above 450 °C but below base metal melting point
   D. In both, the base metal melts
   Answer: C. 450 °C is the dividing line; in brazing the filler still melts below the parent metal. (Key point: Filler melting temperature)

3. What distinguishes welding from soldering and brazing?
   A. Only welding uses flux
   B. Welding uses lower heat
   C. Welding uses a filler of different composition
   D. In welding the parent metal itself melts and fuses, giving the highest strength
   Answer: D. Soldering and brazing do not melt the parent metal; welding does. (Key point: Welding principle)

4. Which is true of brazing?
   A. It joins by capillary action and can join dissimilar metals with less distortion than welding
   B. It uses tin-lead solder
   C. It melts the base metal
   D. It produces the weakest joint of the three
   Answer: A. Brazing uses capillary action in a thin gap, joins different metals and uses less heat than welding. (Key point: Brazing features)

## Related in Workshop Technology

- [Soldering process and fluxes](https://www.bctengineer.com/question.md?key=semester_2%2Fworkshop_technology%3Asoldering-process-flux) — Workshop Technology, chapter 3
- [Arc welding: SMAW, TIG and MIG](https://www.bctengineer.com/question.md?key=semester_2%2Fworkshop_technology%3Aarc-welding-smaw-tig-mig) — Workshop Technology, chapter 10

## Related in other subjects

- [Joining processes; welded vs mechanical joints](https://www.bctengineer.com/question.md?key=semester_4%2Fmanufacturing_and_production_processes%3Ajoining-processes-welded-vs-mechanical-joints) — Manufacturing and Production Processes, chapter 12
- [Define, classify project; temporary organization](https://www.bctengineer.com/question.md?key=semester_7%2Fproject_engineering%3Aproject-classification-temporary-team) — Project Engineering, chapter 1
- [Why temporary construction; single and double scaffolding](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Ascaffolding-single-double) — Building Technology, chapter 8
- [Intensive vs extensive; classify given properties](https://www.bctengineer.com/question.md?key=semester_2%2Ffundamental_of_thermodynamics_and_heat_transfer%3Aintensive-extensive-classify-properties) — Fundamental of Thermodynamics & Heat Transfer, chapter 1