Alex just posted a video on how to measure short (internal) tapers - like the ones we have on a D1-X lathe chuck back plate for example. Quite ingenious design (as usual when he solves problems…).
It basically consists of 5 ball bearing balls arranged such that 4 are tangent to both reference surfaces at the same time and the 5th one is tangent to one reference surface 180* from the 2 “base pairs”. A DTI is then used to measure the second reference surface at the 180* location. It is not an absolute measuring tool, but rather a comparative one. Therefore one needs to have a good fitting back plate to begin with. But it does allow the machining of a duplicate plate to very close tolerances. I also think the taper angle needs to be known and set precisely - should be possible as D1-X specifications (or other spindle nose designs) are universal / well defined and the angle can be set accurately with a sine bar.
As a bonus, he also shows his version of a tapping head and a chamfering tool.
Here is the video link:
It basically consists of 5 ball bearing balls arranged such that 4 are tangent to both reference surfaces at the same time and the 5th one is tangent to one reference surface 180* from the 2 “base pairs”. A DTI is then used to measure the second reference surface at the 180* location. It is not an absolute measuring tool, but rather a comparative one. Therefore one needs to have a good fitting back plate to begin with. But it does allow the machining of a duplicate plate to very close tolerances. I also think the taper angle needs to be known and set precisely - should be possible as D1-X specifications (or other spindle nose designs) are universal / well defined and the angle can be set accurately with a sine bar.
As a bonus, he also shows his version of a tapping head and a chamfering tool.
Here is the video link:
