The Standard Model A talking Machine (phonograph) had a unique hub that fit "Standard" records with a hole diameter of about ½ inch. This replacement hub will allow playing the ¼" hole diameter 78 records as well as the original records (with additional adapter).

I found through measurement and trial and error that the hub taper angle appears to be about 6.3 degrees from center.

The Old Crank - Standard Model A

The original brass hub can be pressed out of the platter and the new 3D printed hub can be glued in place.