How Is an Iron Gate Joined Together and Where Do Welds Fail

A single swing gate with a six foot span opens and closes several thousand times a year, and every one of those cycles flexes the corner joints a few thousandths of an inch, which is why the notes at iron gates round rock elizabethbaron start with the joints rather than the pattern. Most gates in Williamson County fail at a weld long before the bars themselves give out.

Which joints carry the load on an iron gate?

The four frame corners and the hinge side upright carry nearly all of the load. The frame is usually square tubing, and the corners are either mitered and welded on the outside face or butted with a full penetration weld. A butted corner with a continuous bead is stronger than a mitered one, because the weld runs through the tube wall.

How are pickets and scrolls fastened?

Pickets are normally welded to the top and bottom rails at two points each, or passed through punched holes in the rail and welded on the back side. Scrolls rely on small tack welds at each contact point, and those tacks are the first thing to loosen. A scroll joined only by tacks will rattle within a few years on a gate near a busy road such as Interstate 35, where truck traffic sends a steady vibration through the posts.

Why do welds crack?

Welds crack where a stiff section meets a flexible one, and where the heat of welding left the steel brittle. A thin picket welded to a heavy rail concentrates stress at the toe of the bead. Moisture then works into the hairline gap, and rust swells the crack open. Expansive clay soil adds to the problem, because a post that shifts even slightly twists the frame and loads the corners unevenly.

What does a collar do?

A collar is a short sleeve or ring of steel that wraps a joint where two bars cross or a scroll meets a bar. It hides the weld and adds surface area, so the joint spreads its load over a wider band. Collars are common on older gates around Old Settlers Park, where forged and hand fitted work survives next to newer machine cut frames.

How can a cracked joint be spotted early?

Look for a thin line of rust running along a weld, or a rust stain that bleeds below a joint after rain. Press each corner by hand with the gate latched. A joint that gives or clicks has a crack that is already through the weld. Caught early, it needs a grinder, a clean bead and fresh primer.

Guide to joint types

Tube corners, picket welds, scroll tacks and collars each fail in a different way and at a different pace. A gate with butted corners, full length picket welds and galvanized steel under the paint will outlast one built with tacked scrolls and thin bead on bare tubing, even when the two look identical from the street.