I'm making pocket holes to connect wood together with a jig, the Kreg 720. The 720 works by moving at an angle (which I'm trying to measure) to ensure the hole is drilled higher on thicker pieces.

The jig makes a hole like this at a 15 degree angle.
[![enter image description here][1]][1]

The 720 works like this:

[![enter image description here][2]][2]

I'm trying to calculate the length of the drill bit which I can set with a stop. The 720 has stops included for common wood, but I like to be exact and I need to understand the geometry of how the 720 works. I zeroed out an angle meter and found that the case is exactly 57 degrees.

[![enter image description here][3]][3]

But! I wanted to make sure that the drilling jig block moved at 57 degrees, so I used my caliper to measure the board thickness block at the bottom and the top. That gave me these measurements.

[![enter image description here][4]][4]

Per this geometry:
[![enter image description here][5]][5]

So $\theta = 45 \deg$ which is intuitive for a jig like this. However, the case seems mounted to match the $57 \deg $ that I measured. I also measured the picture in photoshop and got the $57 \deg $ as well.

I'm confused with how these could be different. Obviously the case doesn't have to match the internals, but $12 \deg$ is a big difference. I'm curious if anyone has looked at this.


  [1]: https://i.sstatic.net/bUICZ.png
  [2]: https://i.sstatic.net/JQByp.gif
  [3]: https://i.sstatic.net/uPlF2.png
  [4]: https://i.sstatic.net/gjLSI.png
  [5]: https://i.sstatic.net/wsdtF.png