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16. Scarfed butt weld

Material. Hand length of 12-mm round section of mild steel and an odd length of the same about 160 mm long.

Additional tools. No special tools needed.


Upset one end of each piece (Fig. 103A). While still hot, but reheating if necessary, the ends should be scarfed (Fig. 103B) by the method shown in Figs 104 and Fig. 105 . Scarfs must fit nicely together while the length of the scarfs should be only slightly more than the thickness of the metal (Fig. 103 C). Most beginners tend to hammer too much and produce long, thin scarfs. This must be avoided.

It is advisable to have a helper for this job although it can be carried out by one person. The anvil must be clean and the hand hammer ready to be picked up without any loss of time. Tongs holding the short length must be a good fit. The fire must be clean.

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Figure 103

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Figure 104

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Figure 105

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Figure 106

Place both scarfed ends in the fire and bring to a full welding heat, keeping them gently on the move. Both must reach welding heat at the same time. If one is heating more quickly than the other, it can be held back on the edge of the fire while the other is allowed to continue heating. Keep tongs cool during this heating.

When welding heat is near, the smith must make sure that the scarf on the short length is upward and the other is facing down into the fire. The helper takes out the short length in the tongs and places it flat and firmly on the anvil face. At the same time, the smith takes the other piece, steadies it with the hand hammer and positions the scarfs, then quickly begins hammering the joint together. As soon as the metal is felt to stick together the helper releases the tongs, the smith turns the job over and hammers the scarf on the other side.

The weld is forged to a square section first, then the corners are removed and the section is rounded up.

Top and bottom swages can be used to finish the section, but the objective here is to master the welding. All of the foregoing can be completed in one heat. Should a second welding heat be needed, care must be taken to restrict the heat to the area of the joint. Overheating the parts of the work not previously upset will cause thinning of the work. This is a common fault.

See Fig. 106 for positioning the weld on the anvil. It is a good idea to tap the pieces lightly on the anvil just before positioning for welding. This removes some of the surface oxides. This is not always necessary with smaller sizes of metal as these oxides are forced out during hammering. Only low-carbon steels can be welded this way without the use of a fluxing agent.

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