FIELD: mechanical engineering. SUBSTANCE: screw has head 1 with groove 2 for a wrench and threaded shank 3. Cylindric part 5 abuts against the threaded shank. The diameter of the part is less than the average diameter of the shank thread. Part 5 goes into conical member 6 to define openings. Shank 3 has conical part 4 the length of which is about four turns of the thread. The length of part 5 is approximately equal to four thicknesses of the sheet. Member 6 is ended by convex friction surface 7 with the radius equal to 0.5 mm. The screw is made in block and made of improved steel having tensile strength of about 1400 N/sq mm or hardened steel. The screw penetrates in the metal sheet in rotation. Heat, which is released between friction surfaces 7 and the sheet, softens the sheet, and contributes to making openings. EFFECT: improved design. 10 cl, 13 dwg
