Welding 101

Wood is wonderful stuff, but I wonder sometimes if woodworkers aren’t hooked on the material so much as they are on the act of creating things with it. That’s the case with me, and that’s why I’m writing about welding in a magazine usually devoted to oak, pine and plywood. Several significant technical advances have hit the world of welding over the past few years, and they’ve made welding more accessible to the average workshopper. Working with iron, steel and even aluminum is more than possible these days; it’s also easy and affordable if you’re interested in trying something new.

You’ve probably noticed how prices for tablesaws, planers, jointers and other machines have held steady or dropped, while quality is on the rise. This same dynamic has started to unfold with welding tools, and it’s gathering steam. High-quality, reasonably priced, easy-to-use welders and cutting equipment are now available. You can even do some pretty serious electric welding these days using a machine plugged into an ordinary 120-volt outlet.

Getting started

Welding involves melting pieces of adjoining metal so they come together as one. A gas flame or an electric arc can supply the heat required. For most applications, electric welding is simpler than gas: you don’t need to rent tanks, and many electric machines are easily portable.

There are two main options for electric welding–stick welders and the new breed of low-cost, portable wire-feed welders. Despite significant differences in ease of use and applications, both systems are based on the same electrical principles. You’ll need an understanding of these before you can make sense of the technology.

During any electric welding operation, an arc jumps from the tip of a handheld welding electrode across a gap that’s 1/16" to 1/8" from the metal being joined. This arc creates enough heat to melt the metal along each side of the joint line (about 6,000ºC worth of heat at the heart of the arc), plus any additional metal added to the weld during the process to boost strength. A ground cable is clamped to the metal item to complete the circuit, allowing electrons to flow. This is the theory behind all electric welding, although how this plays out with stick versus wire-feed systems varies quite a bit.

 

Stick welders deliver their arc and supplemental metal through a consumable rod that’s clamped in place on the end of the electrode. This is the stick, which you need to keep manually pushing into the molten weld pool as it’s consumed. This action takes some practice. Push the rod too close to the underlying metal and it welds itself right to your workpiece, shutting down both the arc and welding action in the process. Hold the stick too far away and your weld strength will drop considerably.

Simple, inexpensive stick welders have been around for years, and they do a fine job for those willing to put in the time to get the technique right. On the downside, workshop-grade stick welders can’t weld aluminum and they give off a fair amount of smoke during use. This is actually intentional, generated by the coating on the outside of the welding rod. This smoke shields the metal from oxidizing while the weld area is molten. Without this protection, the weld wouldn’t form properly. Trouble is, it doesn’t take long for a stick welder to fill your shop with a pungent blue haze. You need a lot of ventilation.

Wire-feed welders

Following the same principles of arc-generated heat as stick welders, wire-feed welders have several advantages. After 15 minutes of practice, most people can lay down a pretty good bead with a wire-feed welder. After a few hours, you’ll be welding like a pro. The short learning curve isn’t the only advantage; the system is also very portable and relatively inexpensive. This is why wire-feed machines are my favourite welding tools.

When I learned to weld 25 years ago, wire-feed welders were stationary, industrial-sized machines weighing hundreds of pounds and costing thousands of dollars. Today, you can buy a compact, brand-name wire-feed welder that weighs less than 50 lb. for about $420. The appearance of machines such as these is the biggest news in the metal-working scene, although that’s not all.

One reason that a wire-feed machine is easier to use than a stick welder is that it doesn’t have a stick. Instead, it uses a thin, consumable wire (usually 0.020" to 0.040" in diameter) that’s automatically fed off a spool and out the tip of the handheld electrode when you pull the trigger. A small motor drive within the welder itself pushes the wire out. This wire melts because of arc heat, adding metal to the weld bead as it’s laid down. By automatically advancing the wire into the weld area, wire-feed machines take a crucial variable out of your hands. Dial in the correct wire-feed rate for a particular job (it’s controlled by a knob on the welder), then you’re set.

 

Another feature of today’s best wire-feed welders is an innovative gas shielding process with roots that go back to the Second World War. At that time, factories supplying Allied forces produced planes, tanks, ships and ammunition five times faster than Axis factories. This was partly made possible by an innovation in welding technology that funnelled a stream of inert gas through the tip of the welding electrode, which protected the vulnerable weld area very effectively from the ravages of oxygen while it was still hot. This process–now dubbed metal inert gas (MIG) welding–has become the industry standard for producing clean, fast and strong welds in both steel and aluminum. Move up just a little from the least expensive wire-feed welders, and you’ll find portable machines capable of using the MIG process. The inert gases involved are typically carbon dioxide, or a blend of carbon dioxide and argon. Hook up a cylinder of so-called shielding gas to your wire-feed welder, dial in the correct volume of gas flow, then start welding. The MIG process yields ultraclean welds, without the billows of smoke common with stick welders. Expect to pay about $750 for a MIG-capable wire-feed welder.

So, do all wire-feed welders need compressed shielding gas to operate? No. By using a self-shielding welding wire with a built-in flux core, you eliminate the need for gas, although the appearance of these kind of welds isn’t nearly as clean as MIG welds. Also, self-shielding wire gives off more smoke than gas-shielded welding (although not as much as stick welding). Wire costs about $35 for an 11-lb. roll of MIG wire, and about $25 for a 2-lb. roll of self-shielding flux-core wire. In the photo at right, you can see the difference between a self-shielding wire weld and a gas-shielded MIG process: While strong enough, the messy weld on the left was made with self-shielded welding wire. The cleaner weld on right was made using a gas-shielded MIG?process

Want to build an aluminum dock frame? How about some rustproof outdoor storage racks? Got some aluminum machine parts that need repair? You can tackle all of these things with a wire-feed welder capable of gas-shielded operation. Just rent a tank of carbon dioxide, install a roll of aluminum welding wire in your machine, then get busy.

 

 

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.

 

 

Brazing

Brazing is a process that uses molten bronze to join steel, cast iron and any ferrous metal without melting them. It’s similar to heavy-duty soldering, except that you need enough heat to make the underlying metal glow red while melting the bronze.

An ordinary propane torch doesn’t deliver quite enough heat for effective brazing (even on light-gauge sheet steel), but an inexpensive upgrade will get you into the game for about $70. This is what you’ll pay for a basic oxypropane torch set. Designed to be screwed onto a disposable fuel cylinder and a second tank filled with oxygen to coax maximum heat out of the combustion, this equipment delivers plenty of heat for most brazing jobs. Sets like this are available at most hardware stores.

The system comes with two simple valves connected to a torch by a pair of rubber hoses. One valve threads onto a disposable oxygen cylinder, and the other attaches to either a propane or an MAPP gas cylinder (which is liquified petroleum gas combined with methylacetylene propadiene). Although MAPP gas is more expensive than propane, it’s actually cheaper to use because MAPP develops a hotter flame, requiring less oxygen than propane. But with replacement MAPP and oxygen cylinders costing more than $10 each, the system can get expensive on anything but small jobs. You’ll get about 25 minutes of brazing time from one oxygen cylinder, and less than half of that if you have the torch cranked right up for heating metals up to 1/4" thick. Will you be doing a lot of brazing? An oxy-acetylene cutting torch works perfectly for this operation, although there’s an even simpler option. Air-acetylene torches of the sort favoured by plumbers are the simplest way of getting plenty of heat. The best versions come with self-igniting torch heads and include a tool caddy shroud that covers the tank, offering all kinds of pockets for extra brazing rods, eye goggles, spare torch tips and marking tools.

Regardless of the heat source involved, you must always begin brazing by cleaning the metal surfaces to be joined using sandpaper, steel wool or a grinder. Parts also need to fit together with less than a 1/16" gap, ideally under clamping pressure. Heat the metal until it’s bright cherry red, then hold the tip of the brazing rod against the joint surface. It’s possible to heat the metal too hot, causing the bronze to flare up and run off the joint without strength. If you have the temperature right, the bronze will melt within a second or two of touching with the weld area, flowing right into the joint gap and into the open pores of the metal, bonding there when it cools. Cleaning the steel beforehand is essential because dirt prevents the all-important intermingling of steel and molten bronze.

Let there be dark

The bright light created by an electric arc welder demands the use of dark-coloured eye protection, but there’s a problem. If the lens is dark enough to protect your eyes, then it’s too dark to see through until the arc is struck. And that means you’re left fumbling around blind until the welding process shows you exactly where you’re welding. At least, that was the problem until the advent of auto-darkening lenses.

Starting at about $100, you’ll find welding helmets that include a lens that darkens in milliseconds whenever bright light hits it. Tip the helmet down and the world looks like it does when you’re wearing a pair of sunglasses. But as soon as you strike an arc, the lens goes dark enough to protect your eyes. This process requires a small amount of electricity, and it’s provided by photovoltaic cells on the front of the helmet. These transform the light energy of the arc into electricity used to trigger the darkening process. Is an auto-darkening welder’s helmet a gimmick? No. Even pros who’ve mastered the skill of striking an arc blind with old-style helmets swear by auto-darkening systems.

You’ll need to protect your eyes while brazing too, although you don’t need as much darkening power to do the job. A lens that’s dark enough to protect while brazing is still light enough to let you see a bit before the metal is heated. Just don’t make the mistake of using brazing goggles while arc welding. The arc is so bright it demands a very dark lens.

 

A word about tanks

Interested in tooling up for oxyacetylene brazing, gas cutting or MIG welding? You need to understand the world of compressed-gas cylinders.

The first and simplest approach involves owning your own cylinders and having them filled (or exchanged for full ones) at a welding-supply outlet. This is usually possible only for the smallest cylinders (up to about 24" tall). These are easily portable, but they run out quickly. If you want to go larger, you’ll need to rent cylinders as well as pay for the gas that fills them. Cost of shielding gas for a MIG welder runs about $60 to $90 for 49"-tall cylinders (plus about $85 per year for the tank rental). Oxygen for this size of tank costs $40, and $90 for a corresponding tank of acetylene.

Where to learn to weld

My first welding experience came in Grade 8 and, to be honest, I wasn’t so keen. The shop was hot and smelly, and my mind was boggled by the tools. Translation? I ruined my plantholder by holding the tip of the torch for too long in the same place. However, it was a different story 20 years later, when I signed up for a night class in art metalwork. I wanted to make some functional art, and over nine weeks, the easygoing instructor helped me to realize my vision–a coat rack in the form of an alien spine.

Whether you want to make artwork, build furniture or do repairs, a course in welding can give you skills to apply to projects. Here’s a sampling of places where you can learn how to bend, shape, cut and bind metal. And if you don’t live in one of the following cities, your best bet to find a beginner welding class is to get in touch with your local community college or the continuing education department of your district school board. –Bob Sexton

Vancouver
British Columbia Institute of Technology
604-434-1610
www.bcit.ca

Calgary
Chinook Learning Services
Calgary Board of Education
403-777-7200
www.chinooklearningservices.com

Sasktoon
Saskatchewan Institute of Applied Science and Technology
866-467-4278
www.siast.sk.ca

Winnipeg
Winnipeg Technical College
204-989-6500
www.wtc.mb.ca

Toronto
Toronto District School Board
Continuing Education
416-338-4000
www.learn4life.ca

Montreal
Institut Technique Aviron de Montréal
514-739-3010
www.avirontech.com

Moncton
New Brunswick Community College
800-664-1477
www.nbcc.ca

Halifax
Nova Scotia Community College
866-679-6722
www.nscc.ns.ca

Charlottetown
Holland College
800-446-5265
www.hollandc.pe.ca

St. John’s
College of the North Atlantic
888-982-2268
www.cna.nl.ca

If you want to be prepared for class, there are a few items you can gather for your first day:

- Locking pliers
- Work gloves
- Welding goggles
- Measuring tape
- Needlenose pliers
- Safety boots
- 100 per cent cotton coveralls


Export date: Thu Jan 21 14:35:04 2021 / +0000 GMT

This page was exported from Canadian Home Workshop [ https://canadianhomeworkshop.com ]