Cast-toothed wheels require special attention when one of the teeth needs repair. Because the structure of carbon and iron content varies, if not materials, generally poor technique and choice of welding material are culprits. However, with the right precautions and techniques, the teeth can be welded to the gear wheel in full force, and the parts machined to the proper proportions.

Instructions

1. Determine the type of iron used for the gear wheel and teeth; nothing other than white cast iron can be welded. Use the application as a guide: more welded gray iron gears are thrown. Otherwise, be guided by the grain and texture of the metal, or a test sample.
2. Heat the wheel surface and gear the teeth, if possible, in the oven or with a heating coil. For protected arc welding, heat between 500 and 1,200 degrees Fahrenheit. For oxyacetylene welding, heat to between 900 and 1,200 degrees. Do not allow the metal base to approach 1400 degrees or higher, as it may crack. Heating the metal in the proper range prior to welding ensures a high probability of successful welding for cast iron.
3. Weld the tooth back to the wheel by butt welding on all four sides of the tooth. Cast iron welding is ideal; Otherwise, autogenously welding. The less preferred options are use of nickel or steel, as these will cause the base metal to harden beyond manufacturability. Work slowly and steadily during the welding process, to maintain the constant heat reached during the preparatory heating process.
4. Cool welding very slowly to reduce the risk of cracking or other structural compromises.

Tips & Warnings

• Take precaution when welding; Wear all proper safety equipment to protect your body from sparks and hot metal. Test the welding carefully before putting the gear wheel back into service.