holes in the boolit base

[Ausglock]

G'day all.
When I am casting, I cut the sprue and notice some of the boolits have like an air pocket/hole in the base.

Anyone have a clue as to what causes this?

I cast with a Lee 20Lb bottom pour pot and Lee 6 cav molds. Temp is kept at 700 Deg via PID control.
Alloy is 92,6,2 15 BHN
Boolits that do it are mainly 9mm and 357.
I don't seem to have this issue with 40 or 45 boolits.

Thanks.

[runfiverun]

is it a tear or or a void.
a void is from not enough heat in the sprue plate or not quite enough venting.
try loosening the sprue plate nut about 1/8th-1/4 turn.
the tear is timing.

[Zim]

Not enough sprue? If the lead in the cavity cools & the sprue has solidified, it will contract & pull in air. Making a bigger sprue puddles solves this.

[runfiverun]

the larger puddle will also help the heat issue.

[Ausglock]

Thanks.
I'll try a bigger sprue puddle and see what happens.

[fredj338]

I think it's th Lee spru plate myself. I have more issues with this w/ the Lee molds than others. The spalte tends to tear instead of cut. Casting hotter seems to help.

[Ausglock]

Thanks for the replies. The hole is a void. Not a tear.
Would it help if the hole in the sprue plate was bigger?

[Gtek]

Just a thought- are you sure you are real close to level at top off. Maybe just as mold clears out from under pot a very slight rock when still molten and see if you get a burp. Maybe start fill with mold at 30/45 degrees. Each set of blocks can have its own set of rules. Experiment. Gtek

[Dusty Bannister]

Maybe start fill with mold at 30/45 degrees. Each set of blocks can have its own set of rules. Experiment. Gtek[/QUOTE]

And this might just introduce wrinkles on the side of the nose when the alloy hits the cold mold surface. The large sprue puddle should feed the cavity as the alloy cools if the alloy is hot enough to remain fluid. Lee molds like to run hot and if your castings are not frosty, you probably are a bit on the cool side. Either speed up or heat up.

[runfiverun]

it wouldn't be the hole in the plate.
i'd try the heat first.
if that doesn't fix it then you'll need to work on the venting.
backing the nut off a tick or breaking the edge of the mold halves ever so gently will help a lot.
you are trapping air under the edge of the cavity and the sprue plate which won't allow the alloy to fill in the area.

[guicksylver]

O.K. Here's what I found. I was also getting those.
I was placing the spout directly into the sprue plate and waiting a second,
then moving on to the next hole.

Doing this caused a VOID almost every other boolit.

SOLUTION, I placed the spout into the hole, judged when it was almost full then lowered the mold to create a good spure.

Let it run over and be sloopy if you want, but create a large enough spure so it can suck in the extra alloy as it cools.

As stated in other responses "Large spure ,wait for it to frost and DIMPLE"

It's a dance...just have to learn the steps.

[prs]

Ausglock, I cast with a very similar alloy and PID controlled at 700F. I preheat the molds and get them just a little too hot at beginning such that the frosting is a bit much and then let the mold cool over the first few drops. That is opposite of what most folks seem to advise, but I get up and running really fast with great fill-out. I like a light even frosting and I like to see the first cavity filled still molten as the last cavity is topped-up. I keep my mold flat or "plumb" but tend to pour slightly off center into the sprue. That is, the handle end of the mold I call the heel and end where the sprue plate hinges is what I refer to as the toe end. I generally pour from toe to heel, with the lead stream feeding the sprue slightly toward the heel and slightly to my left. This does two neat things: one, at the sprue puddle forms and tends to over-flow that cavity, the flow is toward the toe end, away from the next empty cavity and, two, the molten flow tends to swirl into the cavity while the air escapes with ease. Another fill-out trick or burping trick I employ is to gently rattle the mold as the cavities fill, I kind of shake it as if I had a slight palsy. Its just a gentle shake or vibe. I do not pause between cavities, I keep the flow going and simply move the mold block, thus the heavy sprue is one big strip. I cut the sprue on what I call the third phase change of color; about 7 seconds on these big hot molds. I take great care to be sure my fingers DO NOT touch the sprue plate handle while pouring or cooling. All of this slows the process a little, but there are virtually no culls and we are dropping 6 at a time and I still get about 6 cycles per minute. No air pockets, often do get a slight tear if I rush the opening too much. If I note just the least bit of cutting resistance, I get a nice clean cut.

prs

[detox]

Try hotter 750-800 degrees with mould held about 1/8 to 1/4" away from sprue hole. Seems everyone here on this forum that complains of poor fillout casts much too cool.

[Hamish]

The problem as stated is a void. The remedy has been stated, but let me reinforce it. It is not a heat issue, it is not a result of the size of the hole in the sprue plate.

As the alloy cools in the cavity, the alloy shrinks. If the puddle of alloy on top of the sprue hole is not large enough, then as it shrinking and it is beginning to harden, without enough alloy to shrink back with it, it sucks air through the sprue hole, creating a void.

Turning up the heat until you see the pretty colors of your tin cooking out will not solve the problem. And increasing the size of the hole can either create or solve other problems completely unrelated to the void problem.

prs, nice post sir.

[geargnasher]

Try hotter 750-800 degrees with mould held about 1/8 to 1/4" away from sprue hole. Seems everyone here on this forum that complains of poor fillout casts much too cool.

No, the people who complain about poor fillout haven't learned to manage MOULD TEMPERATURE.

Gear

[btroj]

Bingo.

Mould temp is the key. Get into a good rhythm and everything else just stops mattering as much.

[leadman]

Andy Lee decreased the size of the sprue plate holes at the request of some of their customers. I found this did not let the base fill out properly so opened the holes up to 11/64", the same as the holes in the old Lee sprue plates. Problem solved.
The smaller holes were the same size or slightly smaller than the stream of lead coming out of my RCBS lead pot and I could see the molten lead being spit up just like the pictures of the molten lava in a volcano. Was cool to look at but was conducive to good fill-out.
Now with the bigger holes this does not happen.

[Ausglock]

G'day All.
Thanks for the many replies.
When I am filling to cavities, I have the mold about 1 1/2" below the spout. I have now tried it with the mold only 1/2" below and with a large joined sprue sitting on top. no more voids.

[Echo]

^^^ It's the large sprue that has cured the problem. The large sprue keeps the sprue plate hot, and the alloy molten, so that when the boolits are shrinking, they can suck some alloy down and, Voila! No voids...

[geargnasher]

G'day All.
Thanks for the many replies.
When I am filling to cavities, I have the mold about 1 1/2" below the spout. I have now tried it with the mold only 1/2" below and with a large joined sprue sitting on top. no more voids.

Don't drop the stream any farther than you have to. All the splashing and splattering going on inside the cavity traps air.

Gear