Definition
A soldering method in which solder is first applied to (tinned onto) the mating surfaces of two parts separately, then the parts are fitted together and heated until the solder melts and fuses the joint. The solder flows by capillary action between the closely fitted surfaces, producing a thin, strong, evenly bonded joint without visible solder buildup at the seam.
Plain English
A way of joining two metal parts by coating each one with a thin layer of solder first, then pressing them together and heating them until the solder melts and bonds them into one piece.
Context Anchor
Seen in aircraft maintenance and repair discussions, especially where small metal parts or fittings are joined with solder.
Derivation
The word 'sweat' here comes from the old usage meaning 'to give off moisture by heating' — the solder appears to 'sweat' out of the joint as it melts and flows between the surfaces.
Why Pilots Care
A poor sweat-soldered joint can loosen or fail from heat, vibration, or stress, so the quality of the joint matters in any aircraft part where this method is approved.
Grounding Statement
Picture two flat metal faces with a thin layer of solder between them, heated until that layer melts, spreads, and hardens into the joint.
Intuition Check
Sweat does not mean moisture from a person here. In sweat soldering, it means solder already on the surfaces is melted by heat so it flows between the parts.
Example Sentence 1
The technician used sweat soldering to join the copper fuel line fitting, producing a clean joint with no visible solder around the seam.
Example Sentence 2
Sweat soldering produced a flush joint that passed the structural inspection.