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< prev - next > Manufacturing handicraft process industries Metalworking KnO 100350_Metalworking (Printable PDF)
Practical Action
How to Make a Folding Machine for Sheet Metal Work - Workshop Equipment 1
Rob Hitchings, Practical Action Publishing
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.
How to Make a Rolling Machine for Sheet Metal Work - Workshop Equipment 3
Rob Hitchings, Practical Action Publishing
Specialised 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. This could be as simple as a low cost
jenny. See the Practical Action Technical Brief How to Make a Strengthening Ridge in a
Bucket and How to Make a Metal-bending Machine - Workshop Equipment 10 by R.D.
Mann, Practical Action Publishing.
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.
Pipe Bending
Various low-cost approaches can be applied to this
process as demonstrated in the following two
documents. See the Practical Action Technical Brief
Pipe bending and How to Make a Pipe-bending
Machine - Workshop Equipment 5, Michael Walsby,
Practical Action Publishing.
Cutting and machining
Cutting can be done with a hammer and cold chisel,
which is hard work but often preferable to saws that
wear too quickly.
Another common method is flame cutting if welding
equipment is available.
Tinsnips are used for light work on thin material (up to
about 1 mm steel or 1.5 mm on softer metals). They
are cheap and versatile, but slow, and tend to buckle
the edges of the cut metal.
Various patterns of snips are available, some intended
for cutting deeply into large sheets and others made
more manoeuvrable within the cut. Some have straight
blades, and others, intended particularly for cutting
holes and curved edges, have curved blades.
Figure 4: Flame cutting. Practical
Action organised training for
Asaduzzman Munshi in welding. As a
result he has now started a small
metal workshop of his own, earning Tk
3000 monthly (2000). In the process
of cutting parts for a three-wheel
rickshaw structure. Photo credit:
Practical Action/Zul