The wedges used on my Cutting Gauge are made from either Castello boxwood or African Blackwood. They are produced fractionally over sized on a CNC router so require a little work to make them fit into the mortise. The best way to do this is to lay some fine abrasive paper (320 grit or higher) onto a reliably flat surface rough side up. A machine top or piece of float glass is perfect. Place the wedge on its side and gently start removing material by making long strokes across the paper. Check the fit of the wedge in the mortise frequently and aim for good friction fit, but not too tight. There is no need to adjust the angle.
Over time the mortise might get a little longer (front to back) resulting in the tip of the wedge protruding through he beam. If this happens just trim a small amount off the end of the wedge.