Pipe Trades Workshop
Making a Soldered Joint
The making of a soldered joint can be broken down into 8 simple steps. Most of the steps can be
done quickly, but, for best results, none should be omitted. Often a number of joints are assembled
before soldering (steps 1-6), but this practice is not recommended unless the soldering process is
completed within 2-3 hours of assembly.
1. Measure the length of the tube. This step is simple, but vital. If a piece of tube is too short, it
can result in a poor joint.
2. Cut the tube square. Tube cutters are generally used to cut the copper tube square, but you
can use a hacksaw or an abrasive wheel.
3. Ream cut the end of the tube. Small burrs or slivers left on the end of the tube after cutting
need to be removed by using the reamer attached to the tube cutter.
4. Clean the tube and fitting socket. The end of the tube should be cleaned for a distance of ¼
of an inch more than is required to enter the socket of the fitting. Use sand cloth, special wire
brushes or steel wool to remove all oil, grease, and heavy oxides.
5. Apply a thin film of flux to the tube end and the fitting socket as soon as possible after cleaning
using a brush or swab. Take care not to use too much flux as this will result in excessive flux
inside the joint.
6. Assemble the joint by inserting the tube into the fitting socket, making sure that the tube is
firmly against the end of the socket. Twisting the joint will ensure the flux spreads over both
surfaces. Remove the excess flux with a rag.
7. Apply heat and solder. Heat is usually applied with a propane or butane torch or with an
air-acetylene or an oxyacetylene torch. Begin by applying the tip of the flame to the fitting,
pointing it in the direction of the tube (not into the face of the fitting cup) while keeping the
flame in motion to heat as large an area as possible and avoid overheating one spot. When
you think the joint has reached the proper temperature, remove the flame and apply the end
of the wire solder to the tube at the face of the fitting. The solder should melt on contact with
the tube. If it fails to do so, remove the solder, apply more heat, and try again. If the joint has
been properly made, a ring of solder will almost instantly appear all the way around the joint
indicating that the joint has been filled. Overheating may cause the flux to burn, which requires
taking the joint apart and beginning again from cleaning in step 4. Overheating of cast fittings
may also cause the fitting to crack.
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