Abstract: A thermal insulating material for combustion engine components, which are subjected to combustion gases, e.g. pistons. The insulation consists of a metal layer sintered under low pressure so as to have a porosity of about 25-50% and which is bonded to the engine component by casting of the component onto the porous sintered layer. The exposed or wear-receiving surface of the sintered layer is machined, which not only achieves accurate dimensioning but also closes the pores of the surface.

Abstract: A drill steel for percussion drilling has four longitudinally extending grooves for removal of cuttings. The grooves are shaped such that, in comparison with a hexagonal drill steel, there is obtained an enlarged space for cuttings and a less consumption of material with maintenance of the same resistance to bending.

Abstract: Rock drill bit of the impact type comprising a cylindrical body and a front surface provided with fixed peripherally spaced inserts. The head section of each insert comprises a first and a second working surface. The first working surface is arched in the radial direction of the rock drill bit but planar in a direction perpendicular thereto. The second working surface is quarter-spherical and turned towards the center of the rock drill bit. A transition portion extends between the first working surface and the jacket surface of the insert. The transition portion determines the diameter of the bore.

Abstract: A drilling assembly for use in percussion drilling comprising a drill bit and a drill rod having cooperating conical surfaces, one of said surfaces being provided with a helically extending thread. For purposes of ensuring a reliable connection the thread meets certain geometrical demands and is designed as a left hand thread. Further, the conical surface being provided with the thread is harder than the other conical surface.

Abstract: A percussion drill bit comprises a bit body including a shaft having a conical mounting portion to be mated with a conical mounting portion of a drill rod by means of substantially longitudinal friction forces. An annular row of circumferentially spaced button inserts extend from a front face of the body. A central button insert is disposed centrally of the other inserts and extends axially from the front face of the body beyond the other inserts to define a pilot insert. The outer inserts are inclined at an angle relative to the longitudinal axis of the body. A centrally located flushing channel is provided in the drill rod.

Abstract: A rock drill for percussion drilling comprising a central button insert and a row of outer button inserts. The central button insert extends beyond the outer inserts. For purposes of increasing the drilling rate and the life of the rock drill the ratios of respectively this extent (X) to the diameter (D) of the hole; X:D, and the transverse distance (Y) between the central insert and one of the outer inserts and the diameter (D); Y:D, shall be within predetermined limits.