February 26, 2004
Metal art takes on many forms, from wall hangings to picture frames to fireplace screens. Just ask Jim Truett, a district sales manager for Miller Electric Mfg. Co. by day and artist in his spare time from his Huntsville, Utah, home.
After tracing the fireplace screen pattern on 12-gauge mild steel plate, Jim Truett performed his intricate cuts with an air plasma cutter.
Truett knows his way around a welding power source and its allied tools, consumables and equipment. His job mandates it. But it's Truett's singular ability to combine hardcore metalworking and art that makes his particular specialty so unique.
As his tools of choice to help him create his art, Truett uses a Miller Spectrum® 375 CutMateTM air plasma cutter and Millermatic® All-in-One wire welding power source.
For a recent project, Truett selected 12-gauge mild steel plate for a 40- by 64-in. screen to adorn a stone fireplace. His objective was to incorporate a scene of snow-capped mountains that sits 1 in. below the bottom of each stone on the upper edge of the fireplace.
"The goal was to see the fireplace through the top of the mountains," Truett said. "Trees on the outside edges of the screen go up the side of the river rock in the fireplace to give the scene more depth."
Truett starts with a light cardboardlike material available at office supply stores. For this project he selected a combination of patterns for the fireplace. He typically gathers patterns from various sources and mixes them together to create a one-of-a-kind design for each fireplace.
Truett makes the detailed cuts of the evergreen trees.
"When you have a large pattern like this, you don't need the entire concept all at once," said Truett. "You can take a tree pattern from one place and a wildlife pattern or a landscape pattern from something else and then put them together."
Truett explained that "some patterns I draw and some patterns I just find in a magazine or on the Web. You might see part of a tree that you like and part of a tree that you don't. You use the part you like and draw the other part."
Along with the mountains and evergreen trees, this particular pattern included a moose. "I have a bunch of moose patterns, but this is the one I like best," Truett said. "I was doing a show and a guy who had seen one of my fireplace screens came up to me. He really liked [the screen he saw], and we went over to his house to take down the dimensions of his fireplace. He wanted the moose in his screen." Truett admires this noble animal so much he calls his one-man operation "The Metal Moose."
When it's time to draw, Truett uses a Sharpie® pen or something with a sharp edge to trace the pattern on the material. Some people spray paint the outline and try to follow the pattern, but "the problem there is that the heat of a plasma torch dissipates the lines; a Sharpie or another permanent fine-point marker works the best," Truett said.
A true artist, Truett carefully ensures his screens meet his quality standards.
Once the outline is traced onto the metal, it's time to cut. "In cutting, even how you hold the torch makes a difference," Truett said. "Hold the torch straight up and down."
He explained that the torch can't be held at an angle because a beveled pattern doesn't give the metal the depth required at the edge. "The one thing you need to remember about cutting is this: If you're at an odd angle and you don't feel comfortable, stop. Just stop, reposition yourself, get comfortable, and start cutting again," Truett said.
"The thing I like most about the plasma cutter I use is it gives you the power you want as well as the thin cut, so you can really fine-tune it and follow the line. I'm right-handed, but I use my left hand and put my knuckles down on the backside to steady the torch and my right hand just pulls the trigger. I'm actually using my left hand to follow the line. I try to have a 1/16-in. standoff," Truett said.
He cautioned against stopping and starting on a straight line. Instead, he suggests stopping on an edge because that offers a natural break, and watching for signs of welding tip wear. "What happens is you hold the torch straight up and down and then all of a sudden the cut starts beveling the material. That's when you know it's time to change your tip," Truett said.
Truett saves the final grinding and polishing on the front side of the screen for last so that all of the elements can be blended together.
Next comes the grinding stage. First, Truett turns the pattern upside down so he can remove slag by tapping the metal frame with a piece of metal. Slag left by plasma cutting is easy to remove, but the cuts are so intricate he can't get it all. So he uses a 4 1/2-in. grinder with 40-grit sandpaper to mop all the edges down and make them smooth on the backside.
"Once that's completed, I'll concentrate on the outside edges," Truett said. "I'll flip the frame over and start removing some mill scale to create a design." The sheet metal he uses has mill scale on it, which normally is an imperfection. Grinding mill scale off metal is labor-intensive, but it gives the finished product a shiny look. The mill scale also offers a gray tint to the fireplace, a contrast that the customer wants to keep in the finished piece. He uses his grinder at a 15-degree angle, running the grinder over the edges of the pattern and taking off a fraction of an inch.
"We want this surface smooth because we'll lay the fire screening material on top," Truett said. "We want a clean edge so we can tack the screen on it. After that we're going to outline our edges and smooth all our cuts out."
He uses the grinder on nicks or he'll spot-weld an imperfection to fill it in, and then grind it flat. When he's removing mill scale, Truett uses a maxi disk with a 40-grit count and then switches to a 120-grit wheel to go over the entire frame and take out fine imperfections.
"Your grinder is your friend. Think of it as you would an eraser on a pencil—if you make a mistake, the grinder can correct it," Truett said. "If you're thinking about cutting slowly, don't do it because your hand will shake and the cuts will have wavy edges. If you have to, it's OK to go 1/16-in. outside the pattern. Just keep going smoothly to achieve a straight line; the grinder will bring the cut back in to the proportion you want when you end."
To create his tree effect, Truett employs an up-and-down motion to make it look like cascading evergreen branches; for the moose he uses the edge of the grinder to give depth to the hind quarter, and he creates the front of the moose in a sweeping side-to-side motion like a windshield wiper.
Truett's finished work of art – a fireplace screen featuring a moose, evergreen trees, and snow-capped mountains.
"But I don't do the detail grinding until I've tacked the screen to the back," he explained. "I clamp the screen on the back to ensure that the sides and bottom are square. I use a Bright Mark® valve-action white marker to trace out where to cut the back of the screen and where it needs to be tack-welded to the back of the frame."
There are a number of advantages in using a plasma cutter with a built-in pilot arc controller, and one of them is the ability to cut expanded material such as a metal screen. "What's nice about the [cutter I use] is that the pilot arc stays lit the entire time as we're cutting through the screen material, which makes it easy to cut. Otherwise, the arc would go out and I'd be stuck cutting by hand with a shears. That's slow, tedious and really builds up a cramp."
When it comes time to tack-weld the screen, Truett relies on his all-in-one GMAW unit because of its welding performance and consistent arc starts. He uses a small-diameter welding wire-0.030 or 0.023 in. dia. ER70S-6, a versatile wire that can be used for high-amperage spray transfer as well as to produce smooth weld beads on sheet metal with short-circuiting-type transfer.
While the screen can be welded directly to the frame, doing so without burning away the fine mesh can be difficult. To simplify the process and provide a more secure fastening mechanism, Truett places a small washer (one with about a 1/4-in. hole) on top of the screen and fills in the hole as the basis for tack welds. He spaces the washers 6 to 8 in. apart.
When tack welding, Truett ensures that the contact tip is recessed. "We're doing a lot of flack-tacking, straight up-and-down tacking, and keeping the tip recessed keeps the wire from burning back into the tip," he said. "If you do a lot of tacking, it's probably best to have a quick-change auto hood so you don't have to put your hood up and down on every tack." A clean, flat, heavy piece of steel plate is placed on the frame to aid in holding the screen down.
For tack welds, the contact tip is recessed inside the nozzle about 1/8 in. "I use the outside of the nozzle to push down the screen/washer combination, pull the trigger, and then wait a half-second before I lift the gun up to cool the weld. This helps prevent sticking the nozzle."
When setting the volts and amps on the front of the machine, Truett advises making sure the settings are low enough to tack the screen to the material with penetration, but not so high that you burn a hole in the screen (again, using a washer makes this less important). On his 250-amp/40 percent duty cycle machine, Truett sets the voltage at 16 and the wire feed speed at 175.
"I always use 75/25 [oxygen/argon] shielding gas because it runs cooler and the puddle wets out better on thin material," Truett said. "For tack welding, 0.030-in. wire will work, but 0.024-in. wire works better because it takes less heat to melt and it won't burn your screen away.
"After tack welding the back, the front will have some heat discoloration, so that's why I save the final grinding and polishing on the front side for last. Only then can I blend everything together."
The finished fireplace screen is then ready to take center stage as a conversation piece in its new home, serving as a testament to Truett's skill and artistry.