How Steel Doors Are Made
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Sheet Metal Pressing
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Steel doors are manufactured with hydraulic presses. They shape the door walls and frame from steel channeling and sheet metal. The first step is to cut sheet metal to the proper size to fit over the door frame. This process involves setting the press program to cut sheets of metal (usually 1/4 inch, 12 gage sheets) to the size of the door. Most are about 3 feet wide and 7 feet long. Once the sheets are cut, they are stacked and treated with a sealant or rust protection paint.
The Frame
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The next step is to build the frame of the steel door. The frame is made from 1 1/2 inch steel channel, which is really just a sheet of metal that is bent into a channel shape, meaning two ends are bent at 90 degree angles along the length of the sheet. These channels are cut in the hydraulic press and then welded together by a machine or a certified welder. The channels are tested for strength and then sent on down the assembly line. Most steel doors have only an outer frame, but some will have a reinforced frame the runs diagonally across the door from one corner to another. This reinforcing support is also made from channeling and cut and welded into place.
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Assembly
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The final phase is assembly. The frame of the doors are sent down the line, and the sheets of metal are mounted to them. The sheets are either welded to the door frame using a gas welder, or riveted into place. A machine can apply hot rivets through the sheet metal and into the steel channel bar. The bottom and sides of the doors are treated for rust protection with a sealant, and then the doors are painted. If a knob is to be installed, a hole is cut into the door front and back, and then a slot for the bolt is cut into the frame. The knob assembly is installed in the door and screwed into place with steel screws through holes drilled by a steel drill press.
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