Method of machining an end portion of a long tubular member

Abstract

Thread cutting of the end portion of a long tubular member ( 1 ) held by a chuck system ( 3 ) is carried out with high accuracy without leaving mill scale on the complete thread portion of the resulting threads. The protruding length L of the long tubular member from the chuck system ( 3 ) to the end face of the tubular member is controlled so that the ratio L/D of the protruding length L to the outer diameter D of the long tubular member ( 1 ) is in a range predetermined depending on the outer diameter D and the ratio t/D of the wall thickness t to the outer diameter D of the tubular member ( 1 ). When the chuck system is a floating chuck system having a floating chuck and a positioning chuck, the protruding length L of the tubular member from the floating chuck and the protruding length L′ thereof from the positioning chuck are controlled.

1 . A method of machining an end portion of a long tubular member which has an outer diameter D and a wall thickness t and which is held by a chuck system, characterized by carrying out machining while holding the long tubular member with the chuck system in a position such that the protruding length L of the end portion being machined of the long tubular member from the chuck system satisfying below-described (A) when the chuck system is of the non-floating type and satisfying below-described (B) when it is of the floating type:
 (A) the chuck system is a non-floating chuck system having at least one chuck, and it holds the long tubular member in a position such that the ratio L/D of the protruding length L of the long tubular member, which is the distance from the chuck closest to the end portion being machined to the end face of the end portion being machined of the long tubular member, with respect to the outer diameter D of the tubular member is in the following range:   (1) when the outer diameter D of the tubular member is less than 88.9 mm: if the ratio t/D of the wall thickness t to the outer diameter D of the long tubular member is at most 0.07, L/D is at least 3.0 and at most 4.5; and if t/D is greater than 0.07, L/D is at least 2.5 and at most 3.5;   (2) when the outer diameter D of the tubular member is at least 88.9 mm and at most 139.7 mm: if t/D is at most 0.07, L/D is at least 2.0 and at most 3.5; and if t/D is greater than 0.07, L/D is at least 1.5 and at most 3.5; and   (3) when the outer diameter D of the tubular member is greater than 139.7 mm: if t/D is at most 0.07, L/D is at least 1.5 and at most 2.5; and if t/D is greater than 0.07, L/D is at least 1.0 and at most 2.5;   (B) the chuck system is a floating chuck system having a floating chuck and in front of it a positioning chuck for centering, and it holds the long tubular member in a position such that the ratios L/D and L′/D of the protruding length L of the long tubular member, which is the distance from the floating chuck to the end face of the end portion being machined of the long tubular member, and the protruding length L from the positioning chuck to the end face with respect to the outer diameter D of the long tubular member are in the following ranges:   (1′) when the outer diameter D of the tubular member is less than 88.9 mm: if the ratio t/D of the wall thickness t to the outer diameter D of the long tubular member is at most 0.07, L/D is at least 3.0 and L′/D is at most 3.0; and if t/D is greater than 0.07, L/D is at least 2.5 and L′/D is at most 3.0;   (2′) when the outer diameter D of the tubular member is at least 88.9 mm and at most 139.7 mm: if t/D is at most 0.07, L/D is at least 2.0 and L′/D is at most 2.0; and if t/D is greater than 0.07, L/D is at least 1.5 and L′/D is at most 2.0; and   (3′) when the outer diameter D is greater than 139.7 mm: if t/D is at most 0.07, L/D is at least 1.5 and L′/D is at most 1.5; and if t/D is greater than 0.07, L/D is at least 1.0 and L′/D is at most 1.5.   
   
   
       2 . A method of machining an end portion of a long tubular member having an outer diameter D and a wall thickness t which is held by a non-floating chuck system having at least one chuck, characterized by carrying out machining while holding the long tubular member with the chuck system in a position such that the ratio L/D of the protruding length L of the long tubular member from the chuck closest to the end portion being machined to the end face of the end portion being machined of the long tubular member with respect to the outer diameter D of the tubular member is in the following ranges:
 (1) when the outer diameter D of the tubular member is less than 88.9 mm: if the ratio t/D of the wall thickness t to the outer diameter D of the long tubular member is at most 0.07, L/D is at least 3.0 and at most 4.5; and if t/D is greater than 0.07, L/D is at least 2.5 and at most 3.5;   (2) when the outer diameter D of the tubular member is at least 88.9 mm and at most 139.7 mm: if t/D is at most 0.07, L/D is at least 2.0 and at most 3.5; and if t/D is greater than 0.07, L/D is at least 1.5 and at most 3.5; and   (3) when the outer diameter D of the tubular member is greater than 139.7 mm: if t/D is at most 0.07, L/D is at least 1.5 and at most 2.5; and if t/D is greater than 0.07, L/D is at least 1.0 and at most 2.5.   
   
   
       3 . A method as set forth in  claim 2  wherein machining is carried out on a long tubular member having an outer diameter D of less than 88.9 mm and t/D of at most 0.07 while holding it with the chuck system in a position such that L/D is at least 3.0 and at most 4.5. 
   
   
       4 . A method as set forth in  claim 2  wherein machining is carried out on a long tubular member with an outer diameter D less than 88.9 mm and t/D greater than 0.07 while holding it with the chuck system in a position at which L/D is at least 2.5 and at most 3.5. 
   
   
       5 . A method as set forth in  claim 2  wherein machining is carried out on a long tubular member having an outer diameter D of at least 88.9 mm and at most 139.7 mm and t/D of at most 0.07 while holding it with the chuck system in a position such that L/D is at least 2.0 and at most 3.5. 
   
   
       6 . A method as set forth in  claim 2  wherein machining is carried out on a long tubular member having an outer diameter D of at least 88.9 mm and at most 139.7 mm and t/D greater than 0.07 while holding it with the chuck system in a position such that L/D is at least 1.5 and at most 3.5. 
   
   
       7 . A method as set forth in  claim 2  including carrying out machining on a long tubular member having an outer diameter D greater than 139.7 mm and t/D of at most 0.07 while holding it with the chuck system in a position such that L/D is at least 1.5 and at most 2.5. 
   
   
       8 . A method as set forth in  claim 2  wherein machining is carried out on a long tubular member having an outer diameter D greater than 139.7 mm and t/D greater than 0.07 while holding it with the chuck system in a position such that L/D is at least 1.0 and at most 2.5. 
   
   
       9 . A method of machining an end portion of a long tubular member held by a floating chuck system having a floating chuck and in front of it a positioning chuck for centering, characterized by carrying out machining while holding the long tubular member with the floating chuck system in a position such that the ratios L/D and L′/D of the protruding length L from the floating chuck to the end face of the end portion being machined of the long tubular member and the protruding length L′ from the positioning chuck to the end face with respect to the outer diameter D of the long tubular member are within the following ranges:
 (1′) when the outer diameter D of the tubular member is less than 88.9 mm: if the ratio t/D of the wall thickness t to the outer diameter D of the long tubular member is at most 0.07, L/D is at least 3.0 and L′/D is at most 3.0; and if t/D is greater than 0.07, L/D is at least 2.5 and L′/D is at most 3.0;   (2′) when the outer diameter D of the tubular member is at least 88.9 mm and at most 139.7 mm: if t/D is at most 0.07, L/D is at least 2.0 and L′/D is at most 2.0; and if t/D is greater than 0.07, L/D is at least 1.5 and L′/D is at most 2.0; and   (3′) when the outer diameter D is greater than 139.7 mm: if t/D is at most 0.07, L/D is at least 1.5 and L′/D is at most 1.5; and if t/D is greater than 0.07, L/D is at least 1.0 and L′/D is at most 1.5.   
   
   
       10 . A method as set forth in  claim 9  wherein machining is carried out on a long tubular member having an outer diameter D of less than 88.9 mm and t/D of at most 0.07 while holding it with the chuck system in a position such that L/D is at least 3.0 and L′/D is at most 3.0. 
   
   
       11 . A method as set forth in  claim 9  wherein machining is carried out on a long tubular member having an outer diameter D of less than 88.9 mm and t/D greater than 0.07 while holding it with the chuck system in a position such that L/D is at least 2.5 and L′/D is at most 3.0. 
   
   
       12 . A method as set forth in  claim 9  wherein machining is carried out on a long tubular member having an outer diameter D of at least 88.9 mm and at most 1397 mm and t/D of at most 0.07 while holding it with the chuck system in a position such that L/D is at least 2.0 and L′/D is at most 2.0. 
   
   
       13 . A method as set forth in  claim 9  wherein machining is carried out on a long tubular member having an outer diameter D of at least 88.9 mm and at most 139.7 mm and L/D greater than 0.07 while holding it with the chuck system in a position such that L/D is at least 1.5 and L′/D is at most 2.0. 
   
   
       14 . A method as set forth in  claim 9  wherein machining is carried out on a long tubular member having an outer diameter D greater than 139.7 mm and t/D of at most 0.07 while holding it with the chuck system in a position such that L/D is at least 1.5 and L′/D is at most 1.5. 
   
   
       15 . A method as set forth in  claim 9  wherein machining is carried out on a long tubular member having an outer diameter D greater than 139.7 mm and t/D greater than 0.07 while holding it with the chuck system in a position such that L/D is at least 1.0 and L′/D is at most 1.5. 
   
   
       16 . A method of machining an end portion of a long tubular member as set forth in  claim 9  wherein the centering position of the positioning chuck is located at most 200 mm from the floating chuck.