There are two parts to the Fretz Spinner Ring Jig, used to form the concave band ring in “spinner rings”.
The concave curved stamping mandrel (SRM-1) is designed to flare the band’s edge, one side at a time.
The two-hole steel faced block (SRB-1) is used to support the ring and let the mandrel pass through the ring as it is being flared with a stamping hammer.
Hammer the mandrel’s end to gently flare one side of the ring. Count the blows so the other side can be done later with the same force to maintain symmetry. Finally, place the “spinner band” over the non-flared end of the band and repeat the flaring process to lock the “spinner” on.