To manufacture the firewall presented here, in wire mesh welded on an iron frame, it is better to have some basic knowledge concerning the metal working (cutting, bending) and to have already made some welds or solders successful.
- Metal ruler
- Metal saw
- Refractory Tray
- Locking Pliers
- Oxygen-butane torch
- Filler metal
- Black paint for metal
- Flux cleaner
- Dry point, shears
- Flat iron (20 x 5 mm)
- Square iron (5 x 5 mm)
- Decorative wire mesh
- Preparation of elements
- Assembly of the central part
- Assembling the sides
- Setting up the fence
Preparation of elements
1. Record the measurements of the sides of the frame and mark them on the iron with a scribe. To make the three frames constituting the firewall, use flat iron bars of 20 x 5 mm, usually sold by weight. Press enough on the tip to leave a small furrow in the metal.
2. Using a hacksaw equipped with a 10/12 teeth blade (for cutting the iron), saw following the line of cut. Tighten the iron bar between the jaws of a vice and attack it at a slight angle to avoid breaking the blade.
3. Using a file, bevel the end of the cut bars. The assembly process (weld-on) with filler metal involves the presence of a small V-shaped space to facilitate the connection of two elements. Place the iron bar vertically in the vise so that the end to be adjusted is horizontal. Work with a soft file without pressing too hard on the tool. Try to keep the blade always in the same plane: a sway of the file causes a rounded back-of-a-don on the piece. This image prepares the metal for soldering by stripping it.
4. Draw a precise firewall plan on a strong paper to accurately determine the bend required for the top of the accessory.
Assembly of the central part
5. Place the iron bars between the open jaws of the vise and bend them with small bursts with the hammer tip. If you have an anvil, work on the bigorne (mouth of the anvil). There are hammers to form, which can be used for bending, as well as special devices (bending pliers). Hammer by frequently referring to the plan.
6. Chalk the end of the bend to avoid hammering beyond.
7. Assemble all the parts of the firewall center frame and check the straightness of the corners with a square. If necessary, correct the sides by giving a few lime strokes. The two bent parts at the top of the frame must be perfectly symmetrical.
Assembling the sides
8. The joining of the sides is done by welding. Immobilize the metal parts on an insulating and refractory work plate. In the absence of a tray like this (sold at hardware stores), use refractory bricks: while protecting the workbench, they allow the concentration of heat on the part to be welded. The filler metal rod used here is coated brass, solder suitable for iron. Before carrying out the soldering, it is necessary to pass on the parts to assemble the flow, which avoids the oxidation of the metal during the operation. With the sting of the blowtorch, heat the iron bars until the metal takes a cherry red hue. Then bring the filler metal rod; it flows, by capillarity, into the V between the two pieces. Spread the torch so that the solder cools down.
9. Solder joints can also be made by clamping the pieces between the jaws of a vise. Brazing is carried out using a butane (or propane) torch, which includes a propane cylinder and an oxygen cylinder, two regulators that are placed on the bottles and a torch with lance. You have to work wearing protective glasses. The flame produced by an oxygen-butane torch reaches more than 2800° C. Adjust it before soldering: it must have a bright blue hue. A purple color indicates too much air, and a white color a lack of air.
10. Place the brazed parts, after cooling, between the jaws of the vice and equalize them with the file, this work eliminates the traces of enamel left by the flow. To avoid having to file a large thickness, try to melt only the necessary amount of filler metal. Then check the weld bead, making sure that the V between the pieces is filled. In a successful solder, the assembly produced has substantially the same strength as a single piece.
Setting up the fence
11. Place the finished frame on a sheet of wire mesh. Secure the frame and grill with clamps and trace the inside of the frame to the fence with a dry point. Insist on digging a very visible furrow so you do not make a cutting error.
12. Cut the topsheet using large curved blade shears following the cut line. Operate slowly because the cutting of curves presents some difficulties: shear from inside to outside. Place the wire fence so that the part to be cut is sticking out of the table. Hold the shears with one hand and hold the fence firmly with the other. Ensure your position before starting to cut.
13. Using the file, with the firewall frame tight in the vice, clear the edge and etch the metal to prepare for the solder. It should be an assembly every 10 cm and file the frames on both sides of the firewall in the same way. An application of trichlorethylene substitute on the parts to be welded degreasing; avoid touching them after this operation. Then apply the stripping flux on the filed parts.
14. Solder the inner square iron. The toasting sheet will be held between two square irons, welded inside the frames. This square iron, 5 x 5 mm, must be shaped in the same way as the flat iron and bent by hammering with the failure of a hammer. The section of the bar being less important, the operation presents less difficulties. But it is necessary that the flat and square curved pieces have the same shape and touch in all points, which requires care and meticulousness. During soldering, hold the two joined irons together with a pair of locking pliers, equipped with a device to hold the jaws tight. Before soldering, file the square iron (as you did for the flat iron).
15. Weld the hinges for the articulation of the three frames. Immobilize the parts with pliers-vices after having degreased (trichlorethylene substitute) and coated flux flux. Before the operation, ensure that the frames are properly aligned so that the firewall is not wobbly. The hinges should be at the same height on each side. The hinges used here, with undrilled fixing plates, are called "grid hinges".
16. After placing the topsheet, weld the second square iron to secure the screen. Holding the pieces with vise grips, work on the refractory plate. Place the screen in the same way on both sides of the firewall.
17. With the file, clean all welds made by removing excessive thicknesses of chilled metal. Place the firewall on a horizontal plane and file while keeping the file in this same plane, to avoid the roundings. After filing, the sides of the frames should look smooth.
18. When finished, use special black paint for parts exposed to fire. This painting applies to the brush. Degreasing the firewall with trichlorethylene substitute facilitates the attachment of the paint. Several layers (at least two) are needed.
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