Mold making?

[WestKentucky]

How are bullet molds made? For the lube grooves and whatnot to be features of the mold, a simple drilled or killed hole wouldn’t work. Seems like an EDM might work, but more likely a custom ground sidecutting endmill would do the trick. That sounds expensive and would make molds somewhat expensive. Last option would be for the plates to be cast around an item to make the shape. All seem fairly expensive for manufacturing and I can’t figure out how molds are as cheap as they are.

Does Anybody actually know how a set of molds are made?

 

[kcofohio]

Think turning on a lathe with a faceplate. Lube grooves and nose turned with a formed bit.

 

[WestKentucky]

Think turning on a lathe with a faceplate. Lube grooves and nose turned with a formed bit.

That’s kinda what I expected, but the corners of lube grooves and other features would wear quickly and would likely make for short tool life. Complex shape generally would not be the easiest thing to side-mill.

 

[jaguarxk120]

One reason Lyman stopped making square grease grooves on many molds.
Second reason, why custom mold makers charge so much.
Molds with square grooves can be found it just takes some looking.

 

[troy fairweather]

I made some cutters a few years ago to make some molds, got out on the back burner I just need to find some aluminum be enough.

 

[edwardware]

Mold are machined with a mold cherry.

 

[WestKentucky]

I made some cutters a few years ago to make some molds, got out on the back burner I just need to find some aluminum be enough.

eBay has a ton of small pieces that could easily be used. I bought a 1ft piece of bar stock 1-1/4x6 a few years ago for a project that was on back burner before the material ever arrived. It’s still marked up and sitting in my junk box. I think it was around 20 shipped back then. Probably a bit more now, but there are plenty chunks available.