How to correctly use a plasma cutter

Carl
By Carl Heideman
Jan 26, 2022 | Shop Work, Plasma Cutter | Posted in Shop Work , Restoration & Renovation | From the Dec. 2012 issue | Never miss an article

Photography by Carl Heideman

Cutting metal is no picnic. Thinner metals can be cut with hand tools, but once the material thickness starts to build, so does the difficulty of cutting—and more drastic tools become necessary. 

These heavy-duty tools usually involve a saw blade, an abrasive wheel or directed heat. Each has its advantages and disadvantages, but directed heat is probably the most versatile.

Historically, oxygen/acetylene torches were the preferred method for cutting metal with heat, but they weren’t the most accurate tools and they left a lot of damage and cleanup in their wake. Today we have something better: the plasma cutter. 

Most plasma cutters blow compressed air through an electric arc. The arc ionizes the air and turns it into a very hot, very tightly directed plasma arc—ideal for cutting metal. These cutters cost more than a basic welder and most also require that you own an air compressor of sufficient capacity.

Few tools match the plasma cutter. Its speed, agility and ability to cut tight shapes are a real boon to quality work. Plus, it eliminates the need to spend big time and money on larger equipment, such as a serious band saw.

We’ll admit that we don’t have a lot of use for plasma cutting until the metal gets around 1/8-inch thick or we have a lot of concave cuts to make. For thinner metals and straight or convex cuts, we often find that an air or electric grinder with a quality cutoff wheel will give us a slightly cleaner, more accurate cut with just a bit of a time penalty.

Nonetheless, if you do a lot of fabricating with thicker metal, a plasma cutter is a pretty wise investment. Follow along as we share some tips for using one of these versatile machines.

Tip 1

We really like this HTP MicroCut 301. It’s compact in size, though not extremely portable. It cuts up to 5/16-inch steel and requires 220 volts and an external air compressor feed.

Miller, Lincoln and other companies have some nice portable 110-volt cutters with built-in air compressors, but they are more costly. The HTP requires hooking up the air line and electric power. Then, much like with a welder, the ground strap is attached to the work, and a hand-held torch makes the cuts.

Tip 2

It’s a good idea to draw the cuts with a dark marker before cutting. Then, just follow the line with the torch.

Tip 3

The torch is held at a 90-degree angle to the work. Speed varies depending upon thickness: The thicker the metal, the slower the cut. Want to make sure you’re not cutting hastily? The sparks should be flying below the work, not up at you.

Tip 4

Working freehand over drawn lines works well if you’ve got a steady hand, but it’s typically beneficial to use a guide to get a really nice cut. We usually make a guide out of a 1/2-inch-thick piece of plywood. The plasma cutter excels when making a concave slice around a guide. This would be difficult with an angle grinder.

Tip 5

Here are three straight cuts in 1/4-inch steel. The first cut was with an angle grinder and a cutoff wheel; it took us just over 30 seconds to get a nice result. Our second cut was with the plasma cutter and didn’t require a guide; it’s not quite as straight, but we made it in 20 seconds. The third cut was made with the plasma cutter and a guide—very nice work done in 20 seconds.

While the plasma cutter often offers some improved speed in cutting—as demonstrated by our 1/4-inch steel cuts—it does require some additional cleanup work to remove the kerf from the edge. This comes off pretty quickly; a chipping hammer can take care of most of it, but we prefer to use a grinding disc to dress the edge nicely.

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Comments
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fearlesfil
fearlesfil New Reader
12/6/21 4:36 p.m.

Should the tip rest on the workpiece?

Cousin_Eddie (Forum Supporter)
Cousin_Eddie (Forum Supporter) Dork
12/6/21 4:42 p.m.
fearlesfil said:

Should the tip rest on the workpiece?

My Miller has a drag tip that is meant to touch the work. I assume other brands offer similar.

Cousin_Eddie (Forum Supporter)
Cousin_Eddie (Forum Supporter) Dork
12/6/21 4:42 p.m.
fearlesfil said:

Should the tip rest on the workpiece?

My Miller has a drag tip that is meant to touch the work. I assume other brands offer similar.

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