picked up 4 fly presses recently but 2 of them had no weights so im thinking of getting suitable sized mild steel balls, drilling a hole through them then getting them hot and drifting the hole to a square taper to suit

casting lead ones would probably be easier?

lead is a bit soft and with use the hole stretches, original ones were cast or forged from iron or steel

 

What if you cast lead balls around pieces of square steel tube? That gives you a pre-formed socket, and you don't have to worry about drilling and drifting.

You can get new balls right down the road from you.  Not sure if the cost of them would be such that you save by making your own.  I'd think, though, that you'd burn up a lot of time and fuel to make your own..... and it just might be better all around to buy them.

I have steel balls in stock up to 8" diameter,

I make hydraulic forging presses

3 1/2" is prob about right for these fly presses

we have square tapered drifts

we regularly swing 7 lb hammers

I can drill a 1/2" hole through a ball in a couple of minutes and a few minutes more to get them hot so it is not difficult for me but thanks for the link

I filed some corners into some exercise weights. I already had them so no cost but they are easy to get. The barbell clamps secure them nicely. I am building a stand to get it off the floor.