Making a living from a small-scale metalworking depends on being able to make products that customers want. So it is important to find out what people are looking for. It is also important to make good quality items that will not fail, and it is important to get the price right.
This technical brief looks at some of the basics of running a small-scale metal fabrication workshops within developing countries.
Metal can be manipulated in a number of ways from casting, blacksmithing or forging to machining and joining to produce all manner of tools and equipment.
Small Scale Metal Workshops
In many developing countries much of the metalworking takes place by the roadside in the open. In Kenya this type of unofficial enterprise is called Jua Kali which means in the sunshine in KiSwahli.
The Practical Action (previously known as ITDG) Jua Kali Project was set up to work with small-scale artisans in the informal sector to create employment & income generating opportunities.
In many instances the equipment that these workshops have available to them is limited. To address this limited access to manufacturing equipment Practical Action has set up tool hire workshops that allows small-scale metal workshops to use expensive equipment such as lathes, drills, and milling machines
How to Make Metal Products
Small-scale foundries often start by casting aluminum as the temperatures required are much lower.
Forging or blacksmithing is one of the oldest methods of making objects from metal. The main item required is a forge where the metal can be heated. The other basic requirements are an anvil, a hammer, and some tools to hold the metal while it is being worked.
Tinsmithing / Sheet Metalwork
Sheet metal work is the process of producing such objects as buckets, boxes, tanks, drums, cupboards, desks, ducting, vehicle bodies, etc, from sheet metal. Traditionally tin was commonly used which gave its name to the process but now steel is often used. In developing countries scrap car bodies are a common source of material.
Tinplate, used for making articles such as funnels, where economy of material combined with ease of working are required, is usually in the thickness range of 0.3 to 0.8 mm. Thickness of galvanized steel in common use range from about 0.7 to 2.5 mm. Aluminum, copper, brass and uncoated steel sheet are used in thicknesses from 0.3 to 3 mm.
Metal Folding and Bending
The simplest approach to use a hammer and anvil to produce the shapes you want. Various designs of low cost folding and bending equipment have been developed based on practical experience.
a] Folding machines work on a variety of principles. For general purposes, such as folding sheet metal to make a box, a box-and-pan type machine is convenient. This consists of a flat table, a clamp to hold down the sheet, and an edge that folds up or down to force over the projecting edge of the sheet. Various configurations are used to allow the bending of intricate shapes such as internally flanged boxes. Another form of bending machine, an angle bender, works by forcing the sheet into a V notch by the action of a blade applied by hand lever or by power. These machines are less versatile but once set up for a particular job, can be quicker in use than a folding machine.
b] Bending rollers are used to make drums and pipes. They consist of three horizontal rollers, one above the other two, arranged so as to bend continuously a sheet fed through them. The top roller is adjustable in height to set the radius of curvature of the bend. The rollers are driven either by a handwheel or by power.
c] Specialized bending machines, particularly used by tinsmiths, include burring machines (usually called jennies), which are used for flanging the ends of containers in preparation for wire edging or for making a folded seam; wire rolling machines, for rolling down the edge of a sheet over edging wire; and beading machines, which, by rolling the sheet between shaped rollers, raise a bead round, for example, a drum. Combination machines are available, which will carry out several tinsmiths’ operations (flanging, beading, wire rolling, crimping, etc), by interchanging rollers.
If you are going to perform a particular action on a regular basis such as creating ridges in the metal it is worth getting some extra equipment.
Three dimensional bending can be carried with a press and dies. A 5-ton fly press can be used to stamp items such as small electrical switch covers. Dies can be made of wood, zinc-based alloy, mild steel, or hardened steel. It is also possible to use a rigid die in conjunction with a rubber block. Presses are best suited to batch production. For one off items, hammers and a variety of dollies which are held behind the sheet being worked can be used.
d] Pipe Bending
Various low-cost approaches can be applied to this process as demonstrated in the following two documents.