The taper to be measured is in pink color. It is mounted between two centres that are installed on a blue sine bar of two brown rollers. The rollers are always fixed to the bar.
Use slip gauge combination to make the highest generatrix of the taper parallel to the surface plate. The parallelism is checked by a dial indicator. Then
sinα = H/L
α: haft taper angle
H: thickness of the slip gauge combination
L: center distance of the sine bar rollers