A Sputnik Sinker mold

thingiverse

This is a mold for casting surf fishing sinkers at home. There are two sinkers that can be made using this mold: a 4-sided sinker and an 8-sided sinker. If you cast them in lead, then they ought to weigh about 4 oz and 6 oz respectively. There are holes in the molds where you can slip in wires before casting, to make holes for the arms. In addition, there are two slots in the top to put the loops in. I've sized them to fit 1.5mm wires. The larger hole in the side serves as the sprue, and the smaller one is the riser. There's a hole in the centre of both halves for an M6 bolt to hold both halves together. You can either 3D print the mold halves and then cast them in another material (like aluminium) so that they don't melt when you pour the lead in, or you can CNC machine the halves. Alternately, you can just 3D print the halves and then just cast the sinkers in resin with a load of lead shot mixed in. If you make one, consider posting a make.