Internal lapping tool

An internal lapping tool comprising:

• a steel mandrel;
• a cast iron head attached on the end of said steel mandrel;
• said cast iron head having two spaced raised arcuate lapping faces thereon, said lapping faces and said head formed as a single continuous element;
• a radially adjustable cast iron insert carried in a longitudinal slot in said head substantially diametrically disposed relative to a midpoint between said two spaced arcuate lapping faces;
• said insert having an arcuate lapping face thereon;
• a lapping compound applied to each of said three arcuate lapping faces;
• and
• a longitudinal moveable wedge member in said mandrel for effecting the radial movement of said insert to force and maintain said three arcuate lapping faces into close contact with the cylindrical wall of a hole being lapped as the arcuate lapping faces wear and the hole is enlarged.

A lapping tool for use with a standard machine which will apply both rotational and longitudinal movement thereto, comprising:

• a cast iron lapping head having a pair of spaced raised arcuate lapping faces thereon, said lapping faces and said head formed as a single continuous element and a slot generally diametrically disposed to a midpoint between said arcuate lapping faces;
• a cast iron insert having an arcuate lapping face thereof carried in said slot;
• a steel mandrel attached on the end of said lapping head;
• said mandrel having located on the other end thereof engaging means for engaging to the rotational motion portion of said standard machine;
• and
• a wedge member located within the central portion of said mandrel and having engaging means on one end thereof for engaging the longitudinal motion portion of said standard machine and having wedge means on the front portion thereof in operative engagement with said insert to expand said insert by the action of the longitudinal portion of the standard machine on said wedge member while said mandrel is rotated by the rotational motion portion of the standard machine to thereby lap the interior surface of a hole in a workpiece.

A method of lapping a hole comprising the steps of:

• providing a soft close-grained cast iron head with two spaced raised arcuate lapping faces on the periphery thereof, said lapping faces and said head formed as a single continuous element;
• providing a slot on said head generally diametrically opposite the midpoint between said two integral spaced lapping faces for carrying a soft close-grained cast iron insert with an integral arcuate lapping face on the periphery thereof;
• applying a lapping compound containing a loose abrasive material to the arcuate lapping faces;
• rotating said head and initially adjusting said insert radially outwardly to force said three lapping faces on said rotating head into contact with the cylindrical wall of the hole to be lapped;
• and
• lapping said hole while maintaining said three arcuate lapping faces on said rotating head in close contact with the cylindrical wall of said hole by continually adjusting said insert radially outwardly as the lapping faces wear and the hole is enlarged during the lapping operation.