I've had a few questions lately on tube calls so here are the answers and maybe this will help a few makers out there or spark a new idea for a better way.
First here is the bit I use;
Drill your blank;
Stop the bit when the point starts to come out the bottom like this;
You should see daylight out the center hole;
Then with a smaller drill bit I drill a few holes from the inside of the call in a half moon shape. This is the material I'm going to remove;
These are the bits for the Dremel and file I use to remove the half moon of material;
Then I grind it away. Now just before I grind the opening I normally turn the call to my finished size and shape at this point but for time line sakes I'm leaving this blank square;
Here's a shot of it with a little more shape and smoothness to it. As you can see the lip stop is a little too thick for my liking and I should have drilled deeper or I could whack it off on the miter saw.
Here's the inside;
Here is one finished;
Larry