Grinding spindle for screw grinder

A grinding spindle for use in a screw grinder, comprising:

• a quill to be mounted on a spindle housing;
• a whetstone provided on a leading end of the quill;
• and
• a flexible drive shaft, rotatably supported through a bearing, provided within the quill for driving the whetstone, and configured to impart torque between the whetstone and the spindle housing, with a rotation axis of the whetstone being inclined relative to an axis of the quill according to a lead angle of a screw groove to be formed in an inner peripheral surface of a work to be mounted on a spindle disposed opposed to the spindle housing, wherein:
• the quill includes a fixing side quill to be fixed to the spindle housing and a leading end side quill having the whetstone mounted thereon and removably connectable to the fixing side quill;
• in connecting portions between the fixing side quill and the leading end side quill, an end face of the fixing side quill perpendicular to the axis of the quill and an end face of the leading end side quill are combined with each other;
• the drive shaft includes a first drive shaft, having flexibility, provided within the fixing side quill such that there is a misalignment of a first end of the first drive shaft and a second end of the first drive shaft along the axis of the quill, wherein the misalignment is solely accommodated by the flexibility of the first drive shaft and a second drive shaft, having flexibility, provided within the leading end side quill such that there is a misalignment of a first end of the second drive shaft and a second end of the second drive shaft along the axis of the quill wherein the misalignment is solely accommodated by the flexibility of the second drive shaft and rotatable integrally with the whetstone;
• the first and second drive shafts are removably connected to each other by a rotary joint;
• and
• the first and second drive, shafts are in direct contact with the rotary joint.