Thread: .311 mold construction

Retrieved: December 07, 2013

I've been wanting to make a bullet mold for some time. I'm not up to making a cherry and cutting a grease grooved mold yet, but I thought a paper patch mold would be a good start. Just make an appropriately-shaped D-bit and go for it.

I then realized I have a use for a plain 5/16" mold for lead slugs for balance weights. Since they get hammered into drilled holes, the standard 135 degree point shape is perfect.

A few years back I bought several Lee round ball molds on one of their closeout specials. They were $10 each, I think. This is the sort of thing I bought them for.

I started by getting a couple of pieces of 5/8" aluminum out of the scrapbox, bandsawing them to size, and putting them together with superglue. Then I drilled and tapped for three screws to hold them together. You can see the punch marks for four; I did that before I decided I didn't want the sprue cutter hole to intersect one of the other holes.

I then faced the block square with the flycutter, tap drilled all the way through, clearance drilled one side, tapped 8-32, and ran some screws through to hold the halves together.

I made the sprue plate out of some cold-rolled steel. Various people have reported it to work okay. A few say aluminum worked for them. I had some 3/16" CRS on hand, so I used that.

If the geometry looks odd, it's because the mold is designed for left-handed use.

A tap with the wooden mallet broke the superglue bond Despite the claims, it doesn't stick aluminum all that well, even though I sanded the surfaces flat and cleaned them with acetone before gluing.

I now have to make some ball-end studs to go onto one set of the holes formerly used to hold the halves together, and another set of cups (probably just simple 90 degree countersinks) for the other side, so locate the mold halves when the handles close.

Best as I can figure, the Lee molds used a 3" cutter to make the semicircular grooves for the handles. I'm going to have to make a toolholder to hold a horizontal flycutter. I also recently found that some hardware stores carry 3" saw blades for some of the little battery-powered saws; if the thickness is right, I can use a stack of those.

Anyway, the only difficult part is aligning the blocks when closing. Making the alignment pins is fiddly work. I keep thinking there ought to be something at McMaster-Carr that I can buy off the shelf, but I haven't discovered it yet.