From what I've measured, the angle is ~34.65*. Therefore the taper is ~17.325*. This is from measuring one of them with calipers, so not exact but really close.
To clarify, here is a drawing of the cone holes in the arms that I'm making.
Hope this helps.
![](http://photos1.blogger.com/blogger/3611/1142/320/cone%20hole.jpg)