Historically, since the time when the craft of blacksmithing originated, various methods had been employed to unite and fasten together separate pieces of wrought iron. The Welding together of separate parts, was and continues to be the most effective manner for the blacksmith to join the metal. For railings, balustrades and similar artistic wrought iron work, welding has been used principally for scrolls or other ornamental forms consisting of two or more parts.
Brazing or Hard Soldering (compared to "soft-soldering" using tin); forms a junction which will handle a certain degree of hammering and bending. Most often copper and brass are used, however; in finer work, when the red or yellow color created by heating; would disturb the effect...silver is used instead. The parts to be soldered must be metalically clean and free from oxide; (in earlier times these parts were actually packed in 'loam' which was made more adhesive by the addition of horse-dung). As an adjunct to the solder, borax or powdered-glass was used. For soldering it is necessary to heat it to the point of being red-hot. Small wrought iron objects were soldered with the aid of the blow-pipe; larger ones: required a charcoal or coke fire. A junction occurs when the solder begins to melt, which is denoted when the flame turns green. In order to keep the parts in position while being soldered, they need to be bound together with wire, or temporarily riveted together.
Puttying and cementing secure a firm connection, when individual parts such as various sizes of tubing; have previously been fit to one another, and already possess a certain degree of hold by themselves. Cementing is also used to set wrought iron into stone or other material.
Riveting was, and continues to be one of the most frequently used methods of joining wrought iron and other metals. It will either render parts immoveable or act as a pivot on which they may turn. One of the parts is tenoned to serve as rivet-pin, while the other is drilled for the rivet-hole, and both parts have holes through which the rivet is passed. The rivet is either a cylindrical pin which is hammered out into a broad shape at both ends or has a head at one end; while the other end is hammered flat, clinched into a shaped head with a riveting-set...or lastly, with both heads sunk; (in which case the rivet-holes are conically widened or countersunk). Small objects are riveted cold, larger ones require that they are done while they are red-hot.
Screwing is used in cases where it may be necessary to separate the work into pieces at a future date. One of the parts holds the male, the other the female-screw, or both parts may have an internal screw into which a separate external screw is driven. The screw may have a cut-head, (sunk or raised), with the end is filed-off flush with the surface. It can have a head like a rivet, with a screw-nut fixing the other end, under which a washer may be placed. Screws are tightened or loosened using a screw-driver, whereas a nut is tightened or loosened with a wrench; (or as it may have been referred to back in earlier times a 'spanner'). There is also an adjustable-screw wrench which can be set to any desired size.
Drawing down and riveting often replaced welding and was and continues to be principally used in flat-iron scroll-work. It consists in placing a piece which is brought down to a thin edge against another. If the piece that is to be fixed is partially or not thinned off, a step-like cut is made at the area where it is to be joined.Intersecting, especially when flat or square wrought iron pieces cross each other, may be done without thinning either of the parts, which are bent outwards, or each part is thinned or 'cut-away' half-way, so that they are flush on both sides. For inserting one bar into another, a fitting hole must he punched or 'drifted'.
Tenoning and pinning of wrought iron, are techniques that are still used by blacksmiths today; to fix everything from cast iron spear-points and pineapples, to balustrades and railings, This method was a frequently used method of fastening, where two or more parts were to be fixed together, by the use of a 'collar'. The wrought iron pieces are generally rectangular or half-round in shape, and at times collars were tightened by means of a wedge. Use of a Wedge was an effective way of joining that can easily be loosened again, but it is mostly used at the end to finish a piece of work.
Folds, the term 'Shrinking on collars' means hammering red-hot rings and hoops over the parts to be secured. As they shrink during cooling they give a firm hold. Folding is only used for sheet-metal made of iron. There are single-folds, double-folds, and overlapping folds.
This article is an edited version of the original text from "A Handbook of Art Smithing"