Many bending or rolling problems crop up frequently during building projects that can not be handled with fingers or pliers and often a lot of head scratching is involved in attempts to find the right method. In general plastics are not amenable to bending or rolling. Some thermo-setting plastics, such as resin castings, may be straightened with low temperature heat. Acrylics like Plexiglas can be bent or formed with moderate heat in an oven. In some cases heating over a candle or incandescent light bulb may soften some plastics enough for light bend Some sheets of wood or plastic have a grain which allows some bending in one direction but not others. An example is C grain balsa used in covering model airplanes. Wood may be soaked or steamed to soften for shaping.
Specialized heated tools, similar to an electric soldering iron with a curving fixture on the end, are commonly used by model shipwrights to form planks. Softer brass, bronze and aluminum, wire and sheets bend well. Some lost wax brass castings can be bent. Most steels are very difficult to work without heat. In general cast items do not bend well without heat. Zamac may be bent slightly, slowly and carefully to straighten bows, but heat may be necessary.
Although some things can be done by hand or with simple tools, bending and rolling of larger pieces are arts that may be difficult without the proper tools. Specialized jeweler's type pliers can handle many small jobs. SPECIALIZED JIGS can be made to bend grabirons, handrail and piping, Any cylindrical object can be used as a form for larger curves, keeping mind that metal has spring so the radius should be slightly smaller than th desired finished one. Sheets can be rolled by using a cylinder in a fashion similar to a pastry rolling pin.
Sharp angles can be bent using a vise and hammer, but heat may temper metal and cause breakage. Frequent heating and annealing may be necessary to soften.
NOTE: All bending should be done slowly to avoid heat buildup.
Hobby sized ANVILS can be used to follow the time proven bending methods used by smiths. Most have conical shaping horns and some have plug-in accessories for special shapes. With some imagination and skill almost any shape may be achieved. To make tee fittings for railing , the end of a length of wire can be flattened with a hammer and anvil and trimmed to shape. Before bending a loop, the flat should be heated and cooled slowly to soften.
Many specialized tools are offered in various other hobby areas, which may be adapted for use.
A simple and inexpensive, bench mountable, model airplane bender can handle many medium sized jobs. The ends handle angles, while the movable pins in center can be set to adjust curve radii. Wire or narrow strips can be drawn between pins for longer arcs.
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Pin wire or strip bender
For the model airplane buffs, different vise clampable hexagonal blocks, resembling large solid nuts, with two pins of various sizes and spacing , are sold as benders. Taking an idea from jewelers , a bench anvil block has many sized holes to mount pins for bending to replace a set of benders with more variation. Additionally, they usually have narrow slits in the sides that can be used for sharper bends.
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JEWELER'S BENCH ANVIL BLOCKS.
Also found in the model airplane section, a fairly rugged arc or loop bender with three nylon rollers (1/4", 3/8", 5/8") can curve wire or strips. Two holes allow bench mounting, but it is more convenient when clamped in a vise. A thumb screw clamps work. Since the handle only turns about 270 °, re-clamping is necessary to complete loops. Other sized rollers and a few improvements can be made easily.
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CURVE BENDER.
Useful for thin strips and sheets, the screws force a wedge shaped edge against work, pressing it into a grooved fitting on base. Angle of bend is controlled by depth of press.
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NWSL Bender
Using the same general principle, a set of vise jaw mountable dies can bend much heavier stock. Held by magnets and aligned by lips, these can be used with any vise large enough.
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VISE BENDER DIES. 3" long.
Unfortunately a little large for delicate bending, this is a true brake. Base must be screwed or clamped to bench. Work is held by a plate clamped to baseplate. Setup is tricky, since allowance must be made for work thickness to align bend and reference line. On thicker pieces, scribing a vee along line eases bending and helps produce shaper bend, without weakening appreciably. In development is a smaller version with some improvements.
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18" Bending brake.
Rolling larger sheets for smokeboxes, boilers and tanks is sometimes very difficult without the right tools. These hand driven rollers ease the process. Radius is set by roller spacing/ Several passes may be required, since there is no calibration on adjustment. There are grooves at roller ends to handle strips.
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2 1/2" roller with wire grooves
Simpler, but able to handle longer pieces for high silos and long tanks or boilers, is this Cherry roller.
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11 1/2" roller
Slight tapers may be rolled by misaligning adjustments. They may also be made by distorting cylindrically rolled pieces. In lieu of very expensive fixtures, rolling more extreme tapers is best done with a truncated cone ala the rolling pin method. The form may be taper turned from hard wood on a lathe.
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