Well casing and method for threading

Abstract

A swaging machine has a head with an axis of rotation and a plurality of holes spaced in a circular array concentric and parallel with the axis of rotation. Shafts extend from each of the holes, each shaft having a supporting portion located on the forward side of the head. Rollers are rotatably mounted to the supporting portions of the shaft, each roller having a conical exterior. A chucking member on the rearward side of the head is engaged by a rotary member to rotate the head. The rollers of the rotating head are brought into engagement with a cylindrical pipe, causing a tapered swaged section to be formed on the end of the pipe. The pipe is then threaded. The pipe is preferably of small wall thickness.

I claim:  
     
         1 . An apparatus for swaging pipe, comprising: 
 a head having an axis of rotation and a plurality of holes spaced in a circular array concentric and parallel with the axis of rotation;    a plurality of shafts, each located in one of the holes, each of the shafts having a supporting portion located on a forward side of the head;    a plurality of rollers, each rotatably mounted to the supporting portion of one of the shafts, each of the rollers having a conical exterior for rotatably engaging and swaging an end of a pipe as the head rotates; and    a chucking member on a rearward side of the head for engagement by a rotary member to rotate the head.    
     
     
         2 . The apparatus according to  claim 1  wherein the chucking member comprises: 
 a plate having a forward side and a rearward side;  
 a hub on the rearward side of the plate concentric with the axis of rotation of the head for engagement by the rotary member;  
 a circular wall protruding from the forward side of the plate, the wall engaging the rearward side of the head, defining a central cavity between the rearward side of the head and the forward side of the plate; and  
 wherein the shafts extend through the holes and have rearward ends that protrude into the cavity.  
 
     
     
         3 . The apparatus according to  claim 1  further comprising a set of bearings located between each supporting portion of each of the shafts and each of the rollers.  
     
     
         4 . A method of manufacturing oil well casing, comprising: 
 (a) providing a swaging head with an axis, a plurality of holes in a circular array concentric and parallel with the axis, a shaft located in each hole, and a tapered roller rotatably mounted on each of the shafts;    (b) rotating the swaging head and bringing the tapered rollers into contact with an end of a cylindrical steel pipe, which is held against rotation, to provide a conical section with an exterior having a selected taper; then    (c) cutting a set of threads on the exterior of the conical section.    
     
     
         5 . The method according to  claim 4 , wherein the pipe has a wall thickness in the range from 0.125 inch to 0.219 inch.  
     
     
         6 . The method according to  claim 4 , wherein the pipe has an outer diameter in the range from 4½ inches to 5½ inches.  
     
     
         7 . The method according to  claim 4 , wherein the pipe has a wall thickness in the range from 0.125 inch to 0.219 inch, and the pipe has an outer diameter in the range from 4½ inch to 5½ inch.  
     
     
         8 . The method according to  claim 4 , wherein in step (c), the threads are cut on a taper angle that is equal to or greater than the taper formed in step (b).  
     
     
         9 . The method according to  claim 4 , wherein in step (c), the threads are cut on a taper angle that is greater than the taper formed in step (b).  
     
     
         10 . The method according to  claim 4 , wherein the taper formed in step (b) is in the range from 0.035 inch per inch to 0.0625 inch per inch, and the threads are formed in step (c) on a taper that is 0.0625 inch per inch.  
     
     
         11 . A method of manufacturing oil well casing, comprising: 
 (a) providing a cylindrical steel pipe with an outer diameter in the range from 4½ inch to 5½ inch and a wall thickness in the range from 0.125 inch to 0.219 inch;    (b) swaging a first end of the pipe to provide a conical section with an exterior having a taper in the range from 0.035 inch per inch to 0.0625 inch per inch; then    (c) forming a set of threads on the exterior of the conical section having a taper that is not less than the taper formed in step (b).    
     
     
         12 . The method according to  claim 11 , wherein: 
 step (b) further comprises swaging a second end of the pipe to provide a conical section with an exterior having a taper in the range from 0.035 inch per inch to 0.0625 inch per inch; and    step (c) further comprises forming a set of threads on the exterior of the conical section of the second end of the pipe with a taper that is not less than the taper on the conical section of the second end of the pipe.    
     
     
         13 . The method according to  claim 11 , wherein: 
 the taper of the threads in step (b) comprises 0.0625 inch per inch.    
     
     
         14 . The method according to  claim 11 , wherein: 
 step (b) comprises providing a swaging head with an axis, a plurality of shafts mounted to the swaging head in a circular array concentric and parallel to the axis of the swaging head, and a plurality of tapered rollers, each mounted to one of the shafts; then    rotating the swaging head while preventing rotation of the pipe and bringing the tapered rollers and the first end of the pipe into contact with each other.    
     
     
         15 . A well casing, comprising: 
 a pipe having an outer diameter in the range from 4½ inch to 5½ inch and a wall thickness in the range from 0.125 inch to 0.219 inch;    a swaged section on each end of the pipe, the swaged section having an exterior with a taper; and    a set of threads formed on the exterior of each of the swaged sections, the threads having a taper that is at least equal to the taper formed on the exterior of the swaged section.    
     
     
         16 . The well casing according to  claim 15  wherein the taper on the exterior is in the range from to 0.035 inch per inch to 0.0625 inch per inch, and the taper of the threads is 0.0625 inch per inch.