The standard taper on the INSIDE of most lathe spindles is Jacobs
2-3-4-??
depending on the bore.

Jon Elson wrote:

Hello,

Does anyone know if there is a standard internal taper used with
the D1-6 spindle mount? I have a Sheldon R-15 lathe, and haven't
been able to figure out what the internal taper is, so that I can get
a dead center.

Thanks for any comments,

Jon