Welding 101

Welding is only half of the process when it comes to building things out of metal. Before you ever get to join parts together, you need to cut them to size and shape first. This involves three options: sawing, gas-flame cutting and–my personal favourite–a high-tech option called plasma cutting.

Sawing

We all know carbide saw blades are good with wood, but can they handle hundreds of cuts through steel? You bet they can. Quietly, behind the scenes, several tool companies now offer metal-cutting chop saws that use carbide blades to cut all kinds of metal without generating sparks and mess. They even cut without burred edges or significant heat buildup.

The Triton steel cutter is one model that I’ve used. It has a 7 1/4″-diameter carbide blade (replacement blades cost about $40) within a completely enclosed shroud. This saw is rated to perform thousands of cuts on a single blade, slicing metal up to 2″ square (hollow or solid). The dirty metal filings (called swarf in the trade) are captured in a small, removable drawer. This saw is surprisingly clean, effective and spark-free.

Plasma cutting

In this case, the word plasma has nothing to do with blood transfusions. Scientists define it as the fourth stage of matter–the next step up after the solid, liquid and gas phases, and one phase down from a laser beam. Plasma cutters were initially developed during the 1960s, and they work by directing pressurized gas (nitrogen or air are typically used) through the nozzle of an electrified, handheld torch. When an arc passes from the end of this torch to the grounded metal being cut, an amazing thing happens.

As the gas flows past this arc, it’s heated and immediately reaches the plasma state as it tops out at more than 16,000ºC. This stream of plasma is also travelling at a whopping 20,000 feet per second as it moves out of the cutter. That’s 10 times faster than bullet from a rifle. Metal doesn’t stand a chance.

The plasma cutter is the tool of choice when it comes to slicing all kinds of metal because of the excellent results it produces. The cut is clean, fast and accurate, but, most important, the plasma cutter doesn’t impart nearly as much heat to the surrounding metal as a conventional oxyacetylene cutting torch.

The only problem right now is cost. Although the lower prices we’ve seen in woodworking machinery are now showing up in the world of welding, they haven’t hit plasma cutters yet. For the time being, plasma cutters still cost as much as a good cabinet saw.

Cutting with a torch

Right now, most serious ferrous-metal cutting in home workshops is done with an oxyacetylene cutting torch. The two compressed gases involved–oxygen and acetylene–combine inside the torch before coming out and burning in a stable and balanced way. Cutting with this kind of gas torch begins by heating the steel or iron to a dull red, with the torch tip held about 1/4″ away from the surface. Once the metal is hot, press a thumb lever on the torch, which causes an extra blast of oxygen to be introduced to the flame for cutting. A shower of sparks occurs as the torch slices cleanly through the metal. What’s actually happening is rapid oxidization directly beneath the flame–a kind of rusting. The extra oxygen is what makes it all happen.

Is welding for you? If you have the space in your shop, proper ventilation and the interest, then you’re ready to begin. Creating with metal is a blast, and it’s never been easier to tool up for the work.