Help?

[mcswack]

Just purchased some used molds and some of these have the last mold run still in the molds with the overflow on top to "lock" the mold halves together. Is this a normal proceedure? Should I heat to release or hit with a dowel to shear off the excess lead. Thanks for your response. McSwack

[plainsman456]

The molds that i got a while ago all had the last cast still in them.

just use common sense and they will open without heating them up.

[USAFrox]

What kind of mold? Lee 6-banger? Lyman iron mold? Brass? How many cavities? Forcing a Lee 6-banger open against fully-hardened lead is a good way to snap off the sprue handle. I'd heat it up first (a lot depends on what kind of mold, and what material it is made out of).

[BBQJOE]

I've heard of people leaving the last cast in steel molds to help prevent rust.

[Mk42gunner]

It used to be a fairly standard practice to leave the mold filled, this is supposed to prevent rust in the cavities. I do not think it is nearly as effective as storing the mold in a sealed container with desiccant, especially if you live in the humid part of the country.

Personally, I would hit the sprue with a propane torch to soften it a bit before trying to cut it; depending on how old the molds are they might have boolits cast of straight linotype in them.

Robert

[Tatume]

I've seen people leave the last cast in the mold, but they cut the sprue first, and then didn't open the mold. A rubber band keeps the halves together.

[MtGun44]

It DOES NOT prevent rust in reality, even though this commonly
thought to be true.

Bill

[runfiverun]

it can actually promote rust in a cavity.
if they are steel i'd just whack the plate open.
if they are aluminum i'd heat the mold and plate up.

I have no brass molds but suspect i'd heat them up first too.

[ku4hx]

When casting, this is the exact configuration you'll have just prior to cutting the sprew and opening the mold. The only difference will be your freshly thrown solid lead will be hotter, but solid non the less. If you liquify the lead and then open the mold, you'll get liquid lead all over the place. Open the mold as if you just cast the boolit or boolits.

Leaving alloy in the mold does not prevent rusting. Just another old wives tale. Ostensibly, the idea was to keep air (oxygen) away for the cavity surfaces. That just doesn't happen.

[JonB_in_Glencoe]

I'd heat the mold on a hotplate, if you have one, sprue side down, then whack the sprue plate when the alloy is softened.

[375RUGER]

^^^what he said^^^^

[Dusty Bannister]

When casting, this is the exact configuration you'll have just prior to cutting the sprew and opening the mold. The only difference will be your freshly thrown solid lead will be hotter, but solid non the less.

Not so, because the casting in the mold has had time to age harden. Not knowing what alloy was used, is a question. If the lead "puddle" on the sprue it heated, it will soften but the bullet will not go liquid as you suggest. It will be easier to cut and be a lot easier on the sprue plate hinge screw.
You really do not want to take a chance on snapping that screw and the resulting issues. Apply heat, tap the sprue cutter in the correct manner and get on with business as has already been suggested. Dusty

[Gtek]

I am with the don't whack it crowd. I think I would either hot plate upside down, or upside down and VERY gently warm plate with propane till soft or drip and then cut. Gtek

[mdi]

Rather than risk warping the mold with a hot plate or torch, I'd just whack it...

[blikseme300]

I don't believe in whacking the sprue plate, ever. I cut the sprue with a gloved hand when casting. Your aluminum molds will thank you for no pounding abuse. As for storing molds, iron or alu alloy, I place them in a 50-cal ammo can that has a number of desiccant pouches with nothing in the cavities. Here in the high humidity of deep south Texas I have yet to see any rust on any of my molds.

[mdi]

I've only been casting for mebbe 14 years and to my knowledge, the Lee six banger is the only mold to be designed to open by hand. All the other mold manufacturers design the sprue plate to be tapped to open. If there are others, someone please show me...:confused:

[country gent]

Heating the mold to 400-500 degrees will greatly reduce the force needed to cut the sprue of. If molten lead will smearnad mold will need to be cleaned up. It is common to leave a bulet in iron molds then a light drop of oil on the easms joints to fill the minute cavities . The bullet inplace holds the oil in place better.Moder desicants in a sealed container work well alos but remember to dry them in the oven ocassionally. Once full of absorbed moisture they start releasing it. I would warm mold as normal and then lightly tap plate to cut sprue.

[HeavyMetal]

Over the years I've bought many a mold with the last cast left in it, and a dumber idea I've never seen, LOL!

Every mold had some type of rust in it, from very lite to how will this cast ever again!

As for opening the OP's mold? Not enough info to post an answer!

So to be safe I will also suggest heating the mold, on a hot plate or the casting pot never over an open flame or with a torch!

Once the mold nears operating temp the mold can be opened as it was designed and minimize stress on the mold.

A statement was made about whacking molds open. Most standard 2 cavity molds can be opened by hand as can singles, once you move into 4 6 or more cavities you need to crack them open with a solid wood handle.

In my experience most new casters don't think about this issue until after the mold is hot.

I'll outline my procedure for Lyman 4 cavity molds as a guideline:

Nutcracker handles, mold mounted with the sprue plate pointed at me when holding the handles, once the led is poured and a decent sprue is on the plate, the mold is rotated to my right, making the sprue plate on a vertical plane, about an inch or so off a pile of old rags, and the sprue plate struck with a plastic mallet using the pile of rags as a stop.

One sharp rap opens the mold, it does not spin around and cause an damage to itself or the mold, and the plate is not peend either by the mallet or by hitting a hard surface with no padding.

I usually cast with one glove and use two molds in tandum while casting with a hot plate set up with a mold holder. This gives me easy rotation of the molds, an easy way to keep molds at a constant temp, and an easy place to put my full mold while empting the other without fear of it falling!

Now this won't work for the Lee 6 banger's but I posted this so ideas could be created as needed for each mold type.

[runfiverun]

I just open my lyman 4 cavity's with a gloved hand.
and my aluminum 4 and 6 cav's too.
hitting the plate open induces a little bounce that invites a raised nub on the base.

[Hickory]

I treat my molds like I treat my wife,
I don't whack either one.

[JonB_in_Glencoe]

about a year ago, I turned toward the gloved hand approach to opening Sprue plates on all my molds during standard casting sessions.
But, I still stand by my "whack the sprueplate of a heated mold to dislodge an ancient sprue" advice in post #10