Brazing information for Garden Ornament Bicycle Frame – Silver Soldering

Brazing information for Garden Ornament Bicycle Frame

Silver Soldering is my first post for a while.  2018 will be a year I cost the NHS lots of money and family lots of worry, but better days are ahead I am sure. Anyhow, enough of the moaning! My Brother Stephen asked if I could make some repairs to a garden pot holder in the shape of a bicycle. Could I weld up some replacement tube?  Initially I thought I would dust off my Tig welder, since the tube was very thin (about a mm in thickness).  After a little thought I decided however to silver solder the new metal in, and also one broken weld. Depending on application, task and even profession, brazing and silver soldering can mean the same thing. Looking over the job one tube was almost rotted away (see pictures). This formed one side chassis member.  Fortunately it was still whole for part of its diameter, so the length of the replacement material was easy to calculate.

Fixing the problem

Since I didn’t have any small steel tubing I decided to make it out bar stock of the correct diameter.  After cutting away all the rotten tubing the final length of replacement steel was cut. To make it both stronger and also easier to secure in place whist brazing (or silver soldering) the bar was placed in the lathe. Then one end was turned down for some 20mm to the inside dimension of the tube. Next it was necessary to clean up the old steel on the bicycle axle.  The tube side that fits onto the axle was filed to a flat profile. I didn’t want to have either ends of the repair disproportionally heated so drilled out both ends to reduce the amount of steel to heat. In effect making it a specialised tube. The turned down end was slotted into the cut of tubing and the other end located in position on the axle.

The act of applying the silver solder.

The key to any silver soldering/brazing is to ensure the parts are clean and use a specialised flux. If the parts are still rusty or dirty you won’t get a good join. The more effort you put into preparation will pay dividends and give a  greater chance of success.

Stages of Silver Soldering

The right flux, and getting it to all the parts you want the solder to flow to is also critical.  Choosing the right temperature silver solder allows you to join complicated parts together without the chance of everything soldered before falling apart.  This is especially important when for example making a copper boiler. By the correct use of the temperature range available to you can allow some impressive parts to be made. Silver solder requires the parts to become cherry red in colour before the solder itself will flow.  Dipping the silver solder rod into the flux then applying it to the work will tell you if it’s hot enough. On some jobs if the orientation of the part is suitable, you can place small amounts of silver solder and place these onto the areas to braze. Once the solder flows you will see it disappear until there is some excess or maybe even a drip if you put too much on. Before it cools fully make up some citric acid and if possible dip/drop it into the acid.  This will clean the part up extremely well and also neutralise any chemical reaction for around the joint.

Summary

  1. Cleanliness is critical if you want success.
  2. Use a specialised flux
  3. If joining various parts at different times, use the right temperature ranges of solder.
  4. Hold work securely so it doesn’t move during heating.
  5. If you can cut off little pieces of the solder and place around the work its easier to heat.
  6. Dip Solder rod into the flux before applying and heat to minimum of cherry red for all surrounding areas.
  7. Use citric acid to clean up after soldering

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