Casing Exit Mill Assemblies with Replaceable Blade Sleeve

Abstract

A mill assembly having a mill shaft body, removable bearing and removable blade sleeve. The shaft body presents a mounting portion having a plurality of arcuate curved contact faces for transmission of rotational forces.

What is claimed is: 
     
         1 . A mill assembly for cutting in a subterranean location, the mill assembly comprising:
 a shaft body; and   a blade sleeve that radially surrounds a portion of the shaft body, the blade sleeve being removable from the shaft body.   
     
     
         2 . The mill assembly of  claim 1  further comprising a bearing disposed radially between the shaft body and the blade sleeve. 
     
     
         3 . The mill assembly of  claim 2  wherein the shaft body, blade sleeve and bearing are secured together by press fit so that the blade sleeve and bearing are removable from the shaft body. 
     
     
         4 . The mill assembly of  claim 2  wherein the shaft body further includes a mounting portion upon which the bearing and blade sleeve are mounted, the mounting portion having an outer radial surface that is shaped to preclude rotation of the bearing and blade sleeve with respect to the shaft body. 
     
     
         5 . The mill assembly of  claim 2  wherein the bearing is formed of a material that is softer than material forming the blade sleeve and shaft body. 
     
     
         6 . The mill assembly of  claim 5  wherein the bearing is formed of at least one of the materials from the group consisting of: brass; manganese; bronze; alloys including brass, manganese or bronze; and viscoelastomer. 
     
     
         7 . The mill assembly of  claim 4  wherein the mounting portion presents an outer radial surface having at least three arcuately curved contact faces adjoined by corners. 
     
     
         8 . The mill assembly of  claim 7  wherein:
 the mounting portion has a maximum radius as measured from a most distant radial point; and 
 each of the contact faces presents an outer radial surface having a radius of curvature which is greater than the maximum radius of curvature of the mounting portion. 
 
     
     
         9 . The mill assembly of  claim 8  wherein, for each of the contact faces:
 a central portion of the contact face has a radius of curvature that is greater than the maximum radius of curvature of the mounting portion; and 
 a lateral portion of the contact face has a radius of curvature that is smaller than the maximum radius of curvature of the mounting portion. 
 
     
     
         10 . The mill assembly of  claim 4  wherein the mounting portion is axially tapered. 
     
     
         11 . A mill assembly for cutting in a subterranean location, the mill assembly comprising:
 a shaft body having a mounting portion;   a blade sleeve that radially surrounds the mounting portion of the shaft body; and   the mounting portion is axially tapered.   
     
     
         12 . The mill assembly of  claim 11  wherein the shaft body, blade sleeve and bearing are secured together by press fit so that the blade sleeve and bearing are removable from the shaft body. 
     
     
         13 . The mill assembly of  claim 11  further comprising a bearing that is disposed between the shaft body and the blade sleeve, the bearing being formed of at least one of the materials from the group consisting of: brass; manganese; bronze; alloys including brass, manganese or bronze; and viscoelastomer. 
     
     
         14 . The mill assembly of  claim 11  wherein the mounting portion presents an outer radial surface having at least three arcuately curved contact faces adjoined by corners. 
     
     
         15 . The mill assembly of  claim 14  wherein there are between three and twelve contact faces. 
     
     
         16 . The mill assembly of  claim 14  wherein:
 the mounting portion has a maximum radius as measured from a most distant radial point; and 
 each of the contact faces presents an outer radial surface having an axial cross-sectional shape that forms an arcuate segment of a circle having a radius which is greater than the maximum radius of the mounting portion. 
 
     
     
         17 . A method of assembling a mill assembly for cutting in a downhole location, the method comprising:
 disposing a bearing onto a mounting portion of a mill shaft body;   disposing a blade sleeve onto the bearing; and   wherein the mill shaft body, bearing and blade sleeve are press fit together.   
     
     
         18 . The method of  claim 17  wherein the bearing is formed of a material that is softer than material forming the blade sleeve and shaft body. 
     
     
         19 . The method of  claim 17  wherein the mounting portion is axially tapered to facilitate the press fit.