If you’re working on a classic truck, sooner or later you’ll need to cut metal. There are lots of tools designed for these tasks, and many beginners don’t know which tools are essential and which ones they can probably do without. I’ll review several metal-cutting tools in this article, and share my opinions on each one.
My favorite tools for accurately cutting sheetmetal are aircraft shears. These are available in most hardware or big-box stores, and are quite affordable. They come in left (red), right (green), and straight (yellow) versions. Save yourself some money and skip over the yellow shears. They only work well on very thin metal (like used in the heating and air conditioning trade) and they do a lousy job on the heavier metal used for bodywork on classic trucks. I don’t find the left and right designations very helpful since both the red and green shears will cut in either direction (although they cut tighter one way than the other). In fact, their “direction” depends on whether the handles are above the metal or below, and whether you are cutting toward or away from yourself. Change one of these and the so-called left shear will actually cut tighter going right.
As with most tools, people have their favorites. After trying them all, I prefer the Wiss brand (no affiliation). You can buy similar-looking shears at half the price, and (in my opinion) they work about half as well!
Aircraft shears can do both rough and fine cutting. With sharp shears and a little practice you can follow a line within about ten-thousandths of an inch, or shave off a sliver that wide! I trim most of my patch panel with these shears, and I can get the fit good enough that I rarely need to sand or file the patch to fit, and I’m super fussy about my fit-up for welding. I often make a roughing cut first, so I’m taking off about 1/4 inch on the final cut. These shears can cut steel up to 16 gauge, but you need strong hands to cut metal this thick.
For the shears to cut without distorting the metal, the waste material has to curl away. This happens automatically when trimming off a narrow strip but you may have to curl the waste by hand if you trim off more than about 1/2 inch. These shears are not designed to cut through the middle of a sheet, but if you need to do this you can make two parallel cuts about 3/4-inch apart, switching between the right and left shears. You’ll see a picture of this below.
There is a right and wrong way to use these shears. When used correctly, the “good” side of the metal passes over the center pivot with no interference, and the waste piece curls away harmlessly. Do it “wrong” and you will distort the edge as you go. I see a lot of people, even professionals, who haven’t figured this out!
Tin snips are different. They don’t have the compound leverage that aircraft shears have, so it’s pretty difficult to cut anything thicker than 20-gauge steel with them; and while they are excellent for straight cuts, they are very limited for cutting curves. They are superb for cutting thin, soft metals—and for heavy paper, which I use a lot for patterns!
I have some specialized hand shears; one cuts a small ribbon as it goes (good for cutting through the middle of a sheet), one that nibbles one rectangular chunk at a time, and one that cuts a clean V notch (photos below). These may be helpful for some specialized jobs, but they’re not essential.
There is another great tool similar to aircraft shears, but it’s bench mounted and has a heavier capacity. The original is made by the Beverly Company in three sizes. These give you almost the same accuracy as hand shears, but you can cut much faster since the blades are longer and your arm muscles give you more leverage, helping avoid fatigue. The largest Beverly shear can cut steel up to 3/16-inch thick. The smallest one will cut up to 16-gauge steel, and there are import versions available.
Now let’s talk about power tools. Saber saws can be used to cut metal sheet and plate as long as they are fitted with a fine-toothed blade designed for metal. Variable speed saws are ideal, since slower speeds cut best on harder metals like steel. This is one of the slowest ways to cut metal, and it leaves a coarse edge, but it may allow you to get a job done using a tool you already own. A Sawzall is a heavy-duty version of a saber saw. This is good for cutting through formed, multiple-thickness sections like windshield posts.
There are different styles of power handheld shears. The most common type has two blades, the bottom is fixed and the top one oscillates. These are fast, make a clean cut, and allow you to cut curves or straight. There is a similar shear with three blades: two stationary ones on the top and one oscillating blade on the bottom. This style removes a ribbon of metal as it cuts. The three-bladed version leaves a slightly smoother edge, but is more limited in its ability to cut curves.
A nibbler is similar, but it punches out little crescents of metal as it cuts. It leaves a reasonably clean edge and allows you to make the tightest curves of ANY shear, but I dislike them for two reasons. They leave a mess behind (the little crescents that are punched out get stuck in my shoes and tracked everywhere) and there is a shroud that covers the part that does the cutting, making it hard to follow a line precisely.
Last, we’ll discuss tools that cut with an abrasive disc, which are available in lots of widths and diameters. These can start a cut in the middle of a sheet of metal, and although they leave a little swarf on the cut edge, they are fast and convenient. They’re available in plug-in, cordless, or pneumatic styles, and each has advantages and disadvantages. The cordless versions are great since they don’t have an “umbilical cord” trailing behind them. The pneumatic tools are light and many of them are inexpensive. I like my cordless three-bladed shear so much that I seldom use any other tool for rough cutting, and I can follow a line within 1/16 inch—close enough for some jobs. If I need more precision, I cut a little oversize and follow up with aircraft shears.
The following photos show more detail on these metal-cutting wonders. Next month we’ll take a look at welding and smoothing patch panels, which is often one of the most challenging tasks for homebuilders of classic trucks.