Page 90 - Making things move_ DIY mechanisms for inventors, hobbyists, and artists

Chapter 3 Screw It or Glue It: Fastening and Joining Parts 71

Welding is useful for heavy mechanism work, but isn’t as useful at small scales. It also
has a lot of overhead (equipment, safety supplies, and so on) compared to other
fastening techniques. That said, you will definitely feel more hardcore if you learn to
weld, and it always helps to have another fastening technique at your disposal when
the other options just won’t work. For example, one of my former students made
Skybike, a bike you ride upside down, by welding together parts of old bicycle frames
(see http://itp.nyu.edu/~md1660/skybike.html). This project would have been much
more difficult with any other fastening technique.

Brazing
Brazing uses a copper-zinc or silver-based alloy filler with a melting point above 800°F
to glue two pieces of metal together. Although the melting point of the filler is lower
than that of the metals being joined, the metal parts both melt a bit, and this fusion
helps the joint strength.

Copper brazing is a popular way to join tubes for home plumbing systems. Silver
brazing (sometimes inaccurately called silver soldering) is used extensively when
making silver jewelry.

Braze welding is the term used for joining metals with a dissimilar filler rod. Although
these joints are weaker than in traditional welding, the advantages are that you can
join dissimilar metals and minimize any distortion from heat.

Soldering
Soldering traditionally uses a lead-tin filler with a melting point below 800°F, although
lead-free solder is becoming more popular to reduce e-waste, in compliance with the
Restriction of Hazardous Substances directive (RoHS).

Soldering is not a fusion process because the base materials don’t melt, so these joints
are the weakest we’ve talked about so far and are generally only for connections in
electrical components and wires. Even with these components, you should solder only
when there is no other way to make the connection. Solderless breadboards were
created for prototyping purposes, and we’ll talk more about using them in Chapter 6.