lee mold

[686]

some brands put cross venting grove in there molds. it is the vertical grove that goes from top to bottom between the cav. lee does not do this. has any one cut one in a lee mold to help vent the mold like others do? what would it hurt to cit one? thanks

[HORNET]

Adding venting is rarely detrimental and usually helps, sometimes tremendously. I've cut vents between cavities on several Lee's and it really helps fill out those pockets that form on the sides of the boolits after the venting is blocked by the first cavity being fukk of lead. Helps a lot on Lyman's and RCBS's too. Idea freely stolen from a 4 cavity Ohaus that I saw.

[686]

hornet how did you cut yours? did you use a fine hack saw?

[KCSO]

Use a 50 LPI checkering file from Brownell's, works fine and helps fill out.

[44man]

I'm confused, he said a verticle line between cavities that will do nothing at all!

[crabo]

How about a picture?

[leftiye]

44,
It connects all of the vent lines between cavities, so it equalizes the pressure in all vent lines. Plus if it is deep enough it provides escape at the top and bottom of the blocks. Might not do much under the sprue plate though, but if you've beveled the top edges of the blocks, it should improve venting there too for the boolit bases.

[Newtire]

Great idea. I have done vent lines across. That's what I'm going to do with my Lachmiller 311359 clone that doesn't fill out unless things are almost red hot.

[HORNET]

686,
Actually I start the groove with a carbide tipped scribe and take it to the depth of the existing vents with a triangular needle file. The old Ohaus mold looked like they used a 1/8" end mill at about .015" depth.The idea is to provide an unrestricted gas escape path to the outside of the blocks. This seems most helpful on long, skinny boolits (high l/d ratio) and blocks that close very tightly. If there is a tendancy for there to be an unfilled "hot spot/frosted spot" on the side of the second boolit in a two cavity that is toward the filled first cavity, then the first boolit is blocking off the air escape and the mold will probably benefit from this venting.With short, fat designs there may not be any noticeable difference, but it won't hurt anything. You do need to go back and clean out any burrs that this pushes into the existing venting. Old tricks adapted from injection molding plastics, kinda like full perimeter venting (which works really well but is very tricky to do correctly).
Got no way to take pictures but you can get the idea from some of the pictures of multi-cavity molds on the Hensley&Gibbs website. Don't have the link handy at the moment.