How It Is Made
Tubular steel is made from coils of steel formed by rollers into shapes and then welded along a seam. This is called hollow tubing electric welded seam tubing. Another type of steel tubing -- called drawn-over-mandrel, or DOM, tubing -- is formed over a mandrel that is then removed, leaving the outer tube of steel. Drawn-over-mandrel is a higher-quality type of tubing and much more expensive than welded tubing. It also has greater accuracy in dimensioning, which is generally unneeded for ordinary gates.
Steel tubing is available in square, rectangular or round types. The choice of these shapes depends on the taste of the designer or consumer and the requirements of the gate's design. In most cases, square tubing is easier to fit for welding operations. Round tubing requires notching for a precise fit, which can add to the cost of gates. Tubing is preferred over solid bar steel, which is also available in squares, rectangles and bars because it reduces weight and cost. Solid steel does not add additional strength to gates used under normal conditions.
Larger gates, such as double-hung entry gates or vehicle gates on driveways, generally use 2-inch square tubing, with a 14- or 11-gauge wall thickness. Picket gate sizes would most likely use 3/4-inch square tubing or 1-inch square tubing in either 14- or 16-gauge thickness. If you prefer, you can use 3/4-inch round tubing or 1-inch round tubing for softer edges and a more graceful effect.
Pedestrian gates that provide security for walkways and gardens should use slightly smaller proportions of material. For the perimeter of the gates, 1 1/2-inch square tubing in 14-gauge steel, or rectangular 1-by-1 1/2-inch in 14-gauge material thickness is best. Pickets are commonly a half-inch square or 3/4-inch in 16-gauge, depending on the design.
Keep in mind that the materials you choose for your gate should be in proportion to the overall size and style of the gate's design. Using thicker material for a small gate looks out of proportion and detracts from the beauty of the design. Similarly, using thinner materials for a large gate makes the gate look frail and unstable.