Reverse countersinks are hard to come by and quite expensive. This video will show how to make a reverse countersink out of a copper rivet.
The rivet chosen to be made into a countersink should the appropriate sized stem and head for the rivets to be used in the device.
The rivet is secured in the vice and a hack saw is used to make two notches on opposite sides of the head. The notches are cut to the level of the stem.
Pliers are used to bend the cut edge towards the stem on opposite corners.
The bent sides are filed to ensure a smooth and sharp edge. The reverse counter sink is now ready to use.