Fillet joint: This is an example of a fillet-type joint, and the joining process can be found on the “Process” page. The joint is filled and surrounded with nickel bronze filler. This provides a very strong joint which will last for the life of the bike frame. How long is that? Often decades.
Bilaminate Type 1: The bilaminate -type joints are “hybrids” of lugs and fillets. For the Type 1, the top tube is fillet brazed with nickel bronze onto an outer head tube. The inner head tube is then inserted and joined to the outer head tube/top tube assembly with nickel silver.
Bilaminate Type 2: The bilaminate type 2 joint is the reverse of type 1. Here, the head tube is a single piece and is fillet brazed onto a “lug”, into which the top tube is inserted and joined to the assembly with nickel silver.
LUGS: Lugs are investment cast steel and serve as “sleeves” into which tubes are inserted to be joined. Lugs are intended to fit onto tubes with a very tight tolerance, therefore nickel silver is the most common filler metal as it is highly ductile and flows very well. Lugs are available in a variety of designs and geometries. Pre-made cast lugs are strongly preferred; however, custom lugs can be made through fillet brazing and cutting a custom design or geometry at an additional cost.