Flat Mount fixture
This Flat Mount jig can be used to attach Flat Mount caliper mounts to any bicycle frame or fork. The fixture requires a 3/4"(0.750") dummy axle. The 20mm dummy axle option is no longer available. The design geometry is for 140mm or 160mm rotors. The fixture has 140mm written on it because 140mm is the base location for all Shimano or SRAM Flat Mount calipers. If you are building for either 140mm or 160mm rotors this is the correct fixture.
The fixture uses two small small mounting plates. One for frames and one for forks. The frame plate has two pairs of raised features which lock into the caliper mounting slots, keeping them parallel and preventing rotation during welding or brazing. The features are 34mm apart, and in the correct position relative to the axle as per bicycle industry standards. Any standard Flat Mount calipers mount may be used. They may be purchased from Paragon Machine Works, other suppliers, or made by the framebuilder. The fixture is sold with the frame plate as standard. The fork plate may be purchased separately.