Abstract: A screw head for an injection molding machine is mounted to a distal end portion of a screw, and includes a trunk portion and a screw portion, and an undercut portion formed between the trunk portion and the screw portion, wherein a relationship between a shaft diameter e of the undercut portion and a nominal diameter f of the screw portion is defined as:0.74f.ltoreq.e.ltoreq.0.85fand a relationship between the nominal diameter f of the screw portion and a radius r of curvature of the undercut portion is defined as:0.5f.ltoreq.r.

Abstract: A method of coating a metal article comprising the steps of mixing a slurry of carbides or borides of metals selected from the group consisting of metals belonging to groups IVB and VIB of the periodic table, an organic binder and an organic solvent and then spray coating the slurry on the surface of the article, then machining the coating on the article, and heating the article under pressure so that the organic binder in the coating is heated and eliminated, and placing a metallic binder and the coated article in a furnace whereupon the metallic binder is dissolved and combined with the article.

Abstract: A method whereby a base member having a surface on which a wear-resistant layer is formed and a mold member are disposed in opposing relation so as to form a gap between the surface of the base member and the surface of the mold member opposing the surface of the base member. Sintered hard substance grains of a hard substance powder such as material selected from carbides, nitrides and borides of metals belonging to groups IV, V and VI of the periodic table are filled in the afore-mentioned gap along the wear-resistant layer forming surface of the base member. A metal of self-melting alloy is then permeated into a filling-up layer of the sintered hard substance grains. The mold member is thereafter removed and the exposed surface is polished to obtain a fine wear-resistant layer on the base member.