Miniature Soldering Iron

In Figure 1, the numbers denote: 1 - a washer 2 - a sleeve; 3 - base: 4 - cap; 5 - fiberglass; 6-tube; 7 - sting; 8 stopper; 9 - asbestos filament; 10 - heating coil; 11 - handle.
The design of the soldering iron is traditional. A copper tube into which a sting is pressed is attached to a handle made of an insulating material. On the copper tube is wound 2-3 layers of fiberglass, through which the heating coil is wound. Outside the spiral is isolated asbestos thread. The entire heating element is covered with a metal cap from a multi-rod ballpoint pen. The assembly of the soldering iron is carried out in such a sequence. The tube is heated with a powerful soldering iron and pressed onto the shank of the steel base. For greater reliability, drill a hole with a diameter of 0.8-1 mm at the attachment point of the tube and rivet a piece of steel wire or nail in it. The tube is wound with two layers of fiberglass with a width of 40 mm and a nichrome spiral.The spiral is a nichrome wire with a diameter of 0.35 mm (electric iron helix) with a total resistance of 5-5.6 ohms. The beginning and end of the winding is twisted with intermediate lengths 100 mm of copper wire with a diameter of 0.6 mm. The beginning of the winding is fixed on the tube as close as possible to the sting and the nichrome wire is wound with a step of 0.3 mm. Then a thin asbestos cord is wound onto the heater.
A washer is screwed onto the handle and passed through the hole The power cord in the handle and washer is twisted from three insulated flexible conductors. They are passed through three holes in the base and screwed to the washer by installing three bushes. Insulation in the passageway through the holes in the base should be further strengthened with two or three layers of fiberglass. One of the wires using a bandage of bare copper wire is attached to the base shank, this conductor serves to ground the soldering iron tip during operation. The remaining two are designed to connect the heater to the current source. They put a protective casing on the heater and fix it with a stopper made of spring wire.
Transformerto power the soldering iron, it must have good winding insulation Secondary current of about 1 A.
The second design (Fig. 2) is a heater device, it is made of graphite and screwed directly onto the soldering tip. The design of the soldering iron is very simple. The sting is made from a copper rod with a diameter of 5 mm and threaded M5 thread on it. A nut is screwed on the thread until it stops and a metal washer is put on (Fig. 4). Then put on a mica pad about 0.5 mm thick and carefully screw in the heater.
in Figure 2 numbers denote: 1 - pen; 2 - bracket; 3 - sting, 4 - mica gasket; 5 - heater in the assembly; 6 - petal; 7 - mica gasket; 8 - tube; 9 - graphite rod.
The heater is made as follows. In a segment of copper tube tightly inserted and grind flush with the edges of the graphite cylinder. Graphite can be used from galvanic cells or collector brushes of the electric motor. A hole with a diameter of 4 mm is drilled along the axis of the cylinder and the M5 thread is carefully cut.When screwing on the sting, the thread undergoes significant wear, so it is necessary that the thread on the sting is sufficiently clean and its length is minimal. The heater is screwed all the way into the mica pad. Then a washer-petal is put on the sting so that the copper tube of the heater enters the petal groove, and a second mica pad is put on, the second metal washer and the whole package are tightened with an M5 nut. To the bracket sting with a heater attach the same nut. A steel bracket with a thickness of 3.5 mm is attached to the handle of the soldering iron with screws and serves as a conductor for the heater. The second conductor is screwed to the washer-lobe.
The operating voltage of the soldering iron is about 1 V, current approximately 15 A. The soldering iron is fed from the network through a step-down transformer. Due to the fact that the heater current is significant, the supplying flexible conductors must have a section of at least 3x3 mm. Warm-up time of the sting until the working temperature does not exceed 2 minutes. If you increase the heater current, you can reduce the heating time to several seconds. The soldering iron is very durable because its heater is heat resistant and is practically isolated from the oxygen of the air.