Precisely repositioning powder metal components

Abstract

A sintered powder metal (P/M) component has an integrally formed tapered boss surrounding its bolt hole which extends into counterbores in a component to which it is assembled and produces plastic conformance between the boss and the counterbore when the boss is seated in the counterbore. The P/M component can then be removed from the other component and reassembled to it, with the boss fitting perfectly back into the bore with the plastically deformed surfaces fitting back together precisely to determine the relative positioning of the two components. The boss is tapered, a moat may surround it, and the boss may be provided with axial splines and/or be oblong in the axial direction. Bosses such as these may be applied to two components in general, at least one of which is powder metal, such as a main bearing cap, a sensor ring for measuring the timing of an internal combustion engine and a connecting rod bearing cap. Such bosses may also be applied to a casting insert in which the boss is crushed when the die is closed so as to seal off the surrounded hole during casting.

What we claim is:  
     
         1 . A method of precisely positioning two components relative to one another in which at least one of said components is sintered powder metal, comprising: 
 forming said sintered powder metal component with a boss protruding from a surface of said sintered powder metal component;    forming a hole in said other component to which said sintered powder metal component is assembled, said hole being sized and positioned to receive said boss with interference between said boss and hole;    inserting said boss into said hole with sufficient force so as to cause plastic conformance between said boss and said hole;    removing said boss from said hole; and    reinserting said boss in said hole.    
     
     
         2 . The method as defined in  claim 1 , further comprising the step of tapering the boss such that the boss progressively tightens in the hole as it is inserted.  
     
     
         3 . The method as defined in  claim 1 , further comprising the step of forming splines on the outside of the boss, the axial splines deforming as the boss is inserted in the hole.  
     
     
         4 . The method as defined in  claim 1 , wherein said sintered powder metal is formed from a liquid phase sintering powder metal material.  
     
     
         5 . The method as defined in  claim 1 , further comprising the step of forming a moat around a trailing end of the boss, the moat creating a void into which material around the boss may expand.  
     
     
         6 . The method as defined in  claim 1 , wherein the boss is formed to be oblong in one direction to provide an interference fit with the hole in that direction.  
     
     
         7 . The method as defined in  claim 1 , further comprising the step of forming the boss on a powder metal insert for casting, the insert acting as a crush ring to seal molten casting metal from flowing out of the hole.