Rotary borer

In a rotary borer including

• a body which is generally round having a rotation axis, a front and a rear, the body comprising drill steel mounting means for releasably mounting the borer on a drill steel to be rotated in a predetermined rotary direction about the rotation axis in use, and tip mounting means including an anvil formation defining a forwardly extending anvil surface and an opposing retaining formation defining a forwardly extending retaining surface, the anvil surface and retaining surface being forwardly diverging to form between them a correspondingly forwardly extending slot which slot tapers rearwardly at an angle smaller than about 5.degree.;
• and a tip of hard, abrasion-resistant material having a front, a rear and sides tapering toward the rear at an angle which is complemental to the angle of the slot, the tip being operatively received in the slot such that pressure on the tip during boring, in a longitudinal direction opposite to the direction in which boring advances, wedges the tip into the slot to cause frictional retention of the tip in the slot, wherein, relative to the predetermined direction of rotation in use, the anvil surface is arranged to trail the tip, and the retaining surface is arranged to lead the tip, and wherein one of the anvil surface and the retaining surface has a non-planar seat to seat the tip which has a complemental seat formation, the method including applying heat to the retaining surface to cause the retaining formation to deform to open the slot.

A rotary borer including

• a body which is generally round having a rotation axis, a front and a rear, the body comprising drill steel mounting means for releasably mounting the borer on a drill steel to be rotated in a predetermined rotary direction about the rotation axis in use, and tip mounting means including an anvil formation defining a forwardly extending anvil surface and an opposing retaining formation defining a forwardly extending retaining surface, the anvil surface and retaining surface being forwardly diverging to form between them a correspondingly forwardly extending slot which slot tapers rearwardly at an angle smaller than about 5.degree.;
• and
• a tip of hard, abrasion-resistant material having a front, a rear and sides tapering toward the rear at an angle which is complemental to the angle of the slot, the tip being operatively received in the slot such that pressure on the tip during boring, in a longitudinal direction opposite to the direction in which boring advances, wedges the tip into the slot to cause frictional retention of the tip in the slot, wherein the anvil surface, relative to the predetermined direction of rotation in use, is arranged to trail the tip, one of the anvil surface and the retaining surface having a non-planar seat to seat the tip which has a complemental seat formation, in which the anvil formation has a relatively thick cross section and is correspondingly relatively rigid and the retaining formation has a relatively thin cross section and is correspondingly relatively resilient.