In a previous post...

Bending Strap to Angles Greater than 90°

I mentioned a method for using three, equal diameter, rods or disks to measure an obtuse angle accurately.

The same method can be applied to acute angles, although the mathematical relation is slightly different than that for the obtuse case.

The attached diagram should make the procedure clear. 'D' is the diameter of the rod/disk. Theta is the angle to be measured.

Measuring acute angles accurately-acute.jpg