In its early years, it worked with the Friendly Society of Iron Founders, both agreeing to respect the others' strikes.
[1] The union was one of six founders of the Federation of Moulders and Collateral Trades, in 1906, but the federation achieved little, instead becoming a venue for the competing unions to argue over lines of demarcation and not respecting each other's industrial action.
The federation dissolved in 1910, but this led the unions to work together more productively, and from 1912 they negotiated together on pay and conditions.
[1] The union grew more rapidly during World War I, as moulding was increasingly done using machines.
In 1966, it finally joined the successor to the NUFW, the Amalgamated Union of Foundry Workers, at which time it had about 2,000 members.