Grinding cylindrical bores

Abstract

Method of reducing the thickness of a bore of a cylindrical workpiece for use as a gear. The method involves the steps of: mounting a cylindrical workpiece having a horizontal central axis and an outer diameter in a grinding machine; and grinding the bore of the cylindrical workpiece to reduce its thickness using a grinding wheel that has a diameter that is from 40% to 80% of the outer diameter of the cylindrical bore and has a direction of rotation about an axis of rotation that is parallel to the horizontal central axis of the cylindrical workpiece. The axis of rotation of the grinding wheel may be located from 90 degrees to 180 degrees, in the direction of rotation of the grinding wheel, from a plane that extends vertically through the workpiece when it is mounted in the grinding machine. The gear may be one of a planetary, sun, parallel axis or helical gear.

We claim: 
     
         1 . A method of reducing the thickness of a bore of a cylindrical workpiece for use as a gear; the method comprising the steps of:
 mounting a cylindrical workpiece having a horizontal central axis and an outer diameter in a grinding machine; and   grinding the bore of the cylindrical workpiece to reduce its thickness using a grinding wheel that has a diameter that is from 40% to 80% of the outer diameter of the cylindrical bore and has a direction of rotation about an axis of rotation that is parallel to the horizontal central axis of the cylindrical workpiece.   
     
     
         2 . The method according to  claim 1 , wherein the axis of rotation of the grinding wheel is located from 90 degrees to 180 degrees, in the direction of rotation of the grinding wheel, from a plane that extends vertically through the workpiece when it is mounted in the grinding machine. 
     
     
         3 . The method according to  claim 1 , wherein the grinding machine for grinding the bore of the cylindrical workpiece is performed on a 5-axis machining centre. 
     
     
         4 . The method according to  claim 3 , wherein the bore is rotated about a C-axis of the machine whilst the grinding wheel position is maintained stationary. 
     
     
         5 . The method according to  claim 3 , wherein gear teeth are ground on an external surface of the cylindrical workpiece using the same grinding machine. 
     
     
         6 . The method according to  claim 3 , wherein the faces of the cylindrical workpieces are be ground using the same grinding machining. 
     
     
         7 . The method according to  claim 5 , wherein the gear is one of a planetary, sun, parallel axis or helical gear. 
     
     
         8 . The method according to  claim 6 , wherein the gear is one of a planetary, sun, parallel axis or helical gear. 
     
     
         9 . The method according to  claim 1 , wherein a coolant is provided to the grinding wheel and/or workpiece whilst in use to cool the grinding wheel. 
     
     
         10 . The method according to  claim 9 , wherein the coolant is applied to the grinding wheel and/or workpiece via a flat head nozzle. 
     
     
         11 . The method according to  claim 9 , wherein the coolant is applied to the grinding wheel and/or workpiece in a range from 50 to 150 bar. 
     
     
         12 . The method according to  claim 1 , wherein the internal bore is reduced in thickness in three stages: a roughing stage; a semi-finishing stage; and a finishing stage. 
     
     
         13 . The method according to  claim 12 , wherein the grinding process is completed in fewer than 20 roughing steps within the roughing stage, fewer than 10 semi finishing steps within the semi finishing stage, and fewer than 5 finishing steps in the finishing stage. 
     
     
         14 . A gas turbine engine including a gear that has a central bore ground by the method of  claim 1 .