Most of the ｗorn rollers of bulldozers are repaired by hard facing welding. We know that nowadays those rollers are mostly built up by manual welding， except at some well-equipped shops. Thus the effciency of padding is not suffcient and there are not a few faults in the bead condition，the surface accuracy and the shrinkage deformation. We have tried to produce a simplified padding equipment of the rollers with a semi-automatic welder which has recently been popularized at small work shops. We aimed to make this equipment useful for not only the roller-padding but also for any turning welding. We made several experiments to test the effciency of this equipment and it proved to be practically effective. A summary of the results is shown as follows : ? a）The mechanism of the equipment works perfectly and the purpose of the attempt is satisfactory･ b）Padding time of the roller can be reduced to one-third in comparison with the manual welding. c）As the bead is put on the roller along the circumferential direction，the bead surface becomes more smooth and cylindrical accuracy is improved. d）The degrees of thermal deformation are within the permitted extent， and thus after padding the rollers need not be machined to correct the deformity. e）A reduction of expense of padding can be achieved and it proved to be economical. f）A practical operating test has been performed and it proved of great endurance of the built-up rollers.
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