262 



HANDBOOK OF MECHANICAL DESIGN 



PREPARATION OF MATERIALS FOR RESISTANCE WELDING 



Fig. 532. Fig. 533. Fig. 534. Fig. 535. 



Fig. 532. — Round, embossed projections allow the use of flat electrodes. Several projection welds can be made 

 simultaneously. 



Fig. 533. — Pointed or cone-shaped projections are often used on light-gage materials, such as 22 and 24 gage. 



Fig. 534. — Protruding punch out may help to locate parts preparatory to welding. Wliere great strength is not 

 required, the punch out itself is sometimes electroforged down. 



Fig. 535. — Prick punch marks made with round punch (one blow) used in welding thick plates to light-gage sheets 

 to throw up a crater which localizes welding heat and pressure. 



Fig. 536. Fig. 537. Fig. 538. Fig. 539. 



Fig. 536. — Design of embossed corners, formed over one another and welded between V-shaped electrodes. 



Fig. 537. — Almost any form of screw, rivet, or specially headed part can be projection welded. 



Fig. 538. — Slight radius on the end of the rod permits it to be welded to another part without throwing a fin or 

 flash. 



Fig. 539. — The crater or ringlike cavity is filled with the heated metal of the round projection, resulting in close 

 mechanical contact over the whole surface. 



Fig. 540. Fig. 541. Fig. 542. Fig. 543. 



Fig. 640. — A ring projection can be turned or coined on the shaft in order to localize the welding area. 

 Fig. 541. — Similar to Fig. 539, except reversed. 



Fig. 542. — Projection swaged on the edges of a piece, a method of embossing thick plates or strap stock. 

 Fig. 543. — Specially headed screws or studs prepared both to localize weld and to locate the screws without the 

 necessity of using jigs or fixtures. 



