We decided to put up some of the specs to help callmakers using our jig, troubleshoot any issues they may be having. While we have very few issues with out jig, 99% of the issues are with the call locking up. These issues usually pertain to having too small of an exhaust port or minor sanding.
Exhaust port (Fig A) . Our calls use a large exhaust port of 1/2″. These taper down to 1/4″ of the course of 1.5″ (fig C)
Drill depth stops exactly 1/2″ before the end of the toneboard (Fig B)
Our reed are cut at a 45 degree angle on the end (Fig D)
Lastly, if the dimensions you use are exactly to the specs provided in the picture, and you are still locking up, a little sanding is needed (Fig E). A very light (1000 grit) sanding is usually all the needs to be done. This is usually done from the end of the toneboard in the undrilled area (Fig B) and roughly 1/4″ under the reed. The sharp cut at the end of the toneboard can also be rounded over a bit. Another trick, is to run your thumb, under the reed to “flex” it up just a hair to help get enough air under the reed.