Walter
Fellow
1 1/2 x 6 sounds odd - could it possibly be 1 1/4 x 8? If so, Toolpost supply an adaptor.
1 1/2" x 6 was a common thread on older British made lathes. Harrison and Union Jubilee for example. According to this review by Mark Baker a 1 1/2" x 6tpi spindle was an option for the Poolewood. (1 1/4" x 8 was not)