Stabilized down hole drilling motor

1. A down hole drilling motor, comprising:

a stator housing having an exterior surface, an upper end and a lower end, the exterior surface having an upper vane mounting region at the upper end on which are positioned left hand threads, the upper vane mounting region terminating in an upper contact shoulder spaced inwardly from the upper end and a lower vane mounting region at the lower end on which are positioned right hand threads, the lower vane mounting region terminating in a lower contact shoulder spaced inwardly from the lower end;

an upper mounting sleeve having an internal surface on which are positioned threads adapted to mate with the left hand threads of the upper vane mounting region, such that right hand rotation of the stator housing brings the upper mounting sleeve into contact with the upper contact shoulder;

a lower mounting sleeve having an internal surface on which are positioned threads adapted to mate with the right hand threads of the lower vane mounting region, such that right hand rotation of the stator housing brings the lower mounting sleeve in contact with the lower contact shoulder; and

a plurality of vanes being secured at spaced intervals around a circumference of and extending radially from each of the upper mounting sleeve and the lower mounting sleeve, each of the vanes having a length in relation to an outer diameter of the upper mounting sleeve and the lower mounting sleeve which is expressed by a length to diameter ratio of between 3 and 5 to 1, the combined upper and lower vane length covering not less than one fifth and not more than two thirds of the length of the stator housing.

2. The down hole drilling motor as defined in claim 1 , wherein there are an odd number of vanes spaced circumferentially around each of the upper mounting sleeve and the lower mounting sleeve.

3. The down hole drilling motor as defined in claim 2 , wherein there are five vanes.