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Silver solder for capillary joints

How much solder should I use for 20 pipe connections?

Answer: In hard soldering, the solder is drawn into the gap between the two parts (capillary action). The amount is therefore the gap's volume: length × overlap × gap width, plus a little for the small fillet that should stand at the edge. The calculator gives grammes per joint, in total and what length of wire it corresponds to, so you can cut the pieces off beforehand and order correctly. The gap should be where the solder's data sheet says, typically 0.05–0.2 mm.

Formula

Spaltens rumfang = længde × overlap × spaltebredde (mm³)

Lod (g) = rumfang × massefylde ÷ 1000 × (1 + tillæg) (1 g/cm³ = 0,001 g/mm³)

Trådlængde = rumfang × (1 + tillæg) ÷ trådens tværsnit π × d²/4

The joint should lie within the plumb's direction, typically 0.05–0.2 mm. Too large joint does not fill, too small joint presses too hard on the edge plate or creates bonding force that holds the web in place during forming.

Symbols and units in the formula
SymbolMeaningUnit
laengdeJoint length (around a pipe: π × diameter)mm
overlapOverlap (how far the parts go into each other)mm
spalteColumn widthmm
antalNumber of assembliesstk
rhoSolder density (datasheet; silver solder typically 8.9-9.6)g/cm³
tillaegAllowance for hollow-core and spillage%
traadPlumb line diametermm
=Lod i altg
=Solder per connectiong
=Wire length per jointmm
=Total wire lengthm

Validity and source

Source
Capillary gap 0.05-0.2 mm (solder manufacturer's instructions) · volume × density

Does not apply when

  • Calculates with an even gap filled fully. Hard soldering of brass and galvanised goods gives zinc oxide fumes and cadmium-containing solder must not be used. Use local extraction.

Worked example

The calculator's own default values inserted. The figures are calculated with exactly the formula the tool uses.

Substituted

  • Joint length (around a pipe: π × diameter)50 mm
  • Overlap (how far the parts go into each other)6 mm
  • Column width0.10 mm
  • Number of assemblies20 stk
  • Solder density (datasheet; silver solder typically 8.9-9.6)9.20 g/cm³
  • Allowance for hollow-core and spillage20 %
  • Plumb line diameter1.50 mm

Giver

  • Lod i alt6.6 g
  • Solder per connection0.33 g
  • Wire length per joint20 mm
  • Total wire length0.41 m

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Sådan bruger du den

Når du skal hårdlodde en serie samlinger, kan du regne loddet ud og klippe stykkerne af på forhånd. Det giver ens samlinger og mindre spild.

Step by step

  1. Mål samlingens længde, rundt om et rør er det π × diameter.
  2. Mål overlappet.
  3. Skriv spalten.
  4. Skriv antallet af samlinger og loddets data.
  5. Læs gram og trådlængde.

Typical errors

  • At lave spalten for stor.
  • At bruge cadmiumholdigt lod.
  • At glemme tillæg til hulkehlen.

Examples from everyday life

Kobberrør Ø15

Du skal lodde 20 samlinger på Ø15 kobberrør med 11 mm indstik og 0,1 mm spalte.

Joint length (around a pipe: π × diameter)
47.1 mm
Overlap (how far the parts go into each other)
11 mm
Column width
0.1 mm
Number of assemblies
20 pcs
Solder density (datasheet; silver solder typically 8.9-9.6)
9.2 g/cm³
Allowance for hollow-core and spillage
20 %
Plumb line diameter
1.5 mm

It means: Du skal bruge 11.4 g lod i alt, 0.57 g pr. samling. Klip stykker på 35 mm af tråden.

Bund i en messinglampe

Seks lampefødder skal have bunden loddet i, med 314 mm omkreds og 4 mm overlap.

Joint length (around a pipe: π × diameter)
314 mm
Overlap (how far the parts go into each other)
4 mm
Column width
0.1 mm
Number of assemblies
6 pcs
Solder density (datasheet; silver solder typically 8.9-9.6)
9.2 g/cm³
Allowance for hollow-core and spillage
20 %
Plumb line diameter
1.5 mm

It means: Det kræver 8.3 g lod, svarende til 0.51 m tråd.

Rule of thumb

En samling på Ø15 rør tager ca. et halvt gram sølvlod.

How to check the answer

Rumfanget i mm³ × massefylde ÷ 1000 skal give grammene.