# What's the difference between soldering and welding?

**URL:** <https://boards.straightdope.com/t/whats-the-difference-between-soldering-and-welding/222952>\
**Category:** Factual Questions\
**Created:** [January 6, 2004, 3:53am UTC](https://boards.straightdope.com/t/whats-the-difference-between-soldering-and-welding/222952 "2004-01-06T03:53:37Z")\
**Posts on this page:** 3\
**Page:** 2

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**Author:** ![Anachronism](https://avatars.discourse-cdn.com/v4/letter/a/e56c9b/32.png) [@Anachronism](https://boards.straightdope.com/u/Anachronism)\
**Post date:** [January 7, 2004, 1:46pm UTC](https://boards.straightdope.com/t/whats-the-difference-between-soldering-and-welding/222952/21 "2004-01-07T13:46:28Z")

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In Mass. plumbing solder with lead is only banned for water supply pies and still allowable for drains and such. However it is possible in some place it is banned outright just to prevent a plumber fom using it everywhere. Solder with lead is cheap and easier to work with.

In plumbing the solder does make a strong enough physical connection to hold 100+ pounds of water pressure but the pipes als overlap by 1/2" or so and the spaceto be filled is very small.

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**Author:** ![Anachronism](https://avatars.discourse-cdn.com/v4/letter/a/e56c9b/32.png) [@Anachronism](https://boards.straightdope.com/u/Anachronism)\
**Post date:** [January 7, 2004, 3:18pm UTC](https://boards.straightdope.com/t/whats-the-difference-between-soldering-and-welding/222952/22 "2004-01-07T15:18:55Z")

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In Mass. plumbing solder with lead is only banned for water supply pies and still allowable for drains and such. However it is possible in some place it is banned outright just to prevent a plumber fom using it everywhere. Solder with lead is cheap and easier to work with.

In plumbing the solder does make a strong enough physical connection to hold 100+ pounds of water pressure but the pipes als overlap by 1/2" or so and the spaceto be filled is very small.

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**Author:** ![Dag\_Otto](https://avatars.discourse-cdn.com/v4/letter/d/439d5e/32.png) [@Dag\_Otto](https://boards.straightdope.com/u/Dag_Otto)\
**Post date:** [January 7, 2004, 5:55pm UTC](https://boards.straightdope.com/t/whats-the-difference-between-soldering-and-welding/222952/23 "2004-01-07T17:55:41Z")

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In addition, there is a method called friction stir welding which used a rotating pin pressed against the two pieces to be joined. The heat from the friction melts the two and joins them.

[http://www1.msfc.nasa.gov/NEWSROOM/news/releases/2002/02-009.html](http://www1.msfc.nasa.gov/NEWSROOM/news/releases/2002/02-009.html)

I believe that this is being used to weld airplane fuselages together.

(off topic: Is ‘airplane fuselage’ redundant?)

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