Fill out problem

[Jim]

I think I'm in the right section, but if not, please move to appropriate section.

A friend has a Lee 2 cavity mold in .356 RN for 9MM. The front cavity does fine, no problem. The rear cavity won't fill out at the base of the boolit. It will fill up, but not out, making good square corners.
I asked him about his heat settings, they're good. The top of the block halves are clean, the underside of the sprue plate is clean and he piles up a good sprue. He's running 3 % tin in WWs.

Any suggestions on what the problem may be?

[dragonrider]

I am pretty sure it is a venting problem, try lightly, that is LIGHTLY, filing the top edge of the mold halves where they come together, also known as the parting line. A very small, not larger than a vent line, 45 degree flat on each side may do it.

[white eagle]

my guess as well
before hitting with file brush it with stiff
tooth brush
I had a mold with the same issue
did that and cured the stubborn cav.:Bright idea:

[fryboy]

+1 erm +2 on the venting , the rear cavity is also the one closest to the sprue screw and maybe snugger because of it , sometimes a pencil scribed in the area it doesnt want to fill out is also helpful

[geargnasher]

+1 erm +2 on the venting , the rear cavity is also the one closest to the sprue screw and maybe snugger because of it , sometimes a pencil scribed in the area it doesnt want to fill out is also helpful

My thoughts as well. Often a sprue plate will warp, curving upward at the front cavity causing out-of-square (but well-filled) bases, while the rear cavity doesn't vent well because the sprue plate is too tight. Need to do the "daylight" test to see if the plate is flat on the blocks, and also verify pivot screw isn't too tight. I like to run my sprue plates fairly loose and let gravity and the springy wave washer do the work of keeping it flat on the blocks.

Gear

[Jim]

Thanks, guys! 'Preciate it!

[grullaguy]

Thanks from me as well!
Same mold, same cavity, same problem. Out of frustration, I had resorted to only using the further cavity.

[Nrut]

Jim,
Try pressure casting if you are using a bottom pour pot..
When the cavity is full just drop the mold a bit and form a sprue puddle..
Works every time I have poor base fill out..

[milprileb]

Send them back to Lee. They will sort it out pronto.

That is: after you try the solutions offered

[geargnasher]

Jim, I just reread your OP and I have a few suggestions to pass along to your friend if you don't mind. I missed that it was a Lee mould, and if he's not using some sort of quality sprue plate lube around the pivot, the plate will gall the block, making deep, circular gouges in the metal. This "knurling" effect raises ridges which push the sprue plate up on the cavity side, but allow the unsupported side on the left rear corner of the mould to fall, thus causing the plate to lift at an angle. He probably needs to clamp the mould in a vise protected with wooden blocks and remove the sprue plate screw. then take it out of the vise and wet-sand the burrs off of the blocks and sprue plate with 400-grit emery paper backed by a piece of heavy plate glass, at least "double strength" glass if not 1/4". While he has the screw out, it would be a good time to cross-drill and tap the sprue plate pivot screw for a setbolt just like the Lyman two-cavity moulds have, that way he can adjust the tension however he desires without it loosening or overtorquing the pivot bolt.

Gear

[mooman76]

I have a couple Lee moulds that have that problem and I cured it by loosening the sprue plate so that would tend to go along with what the others thought, that it is a venting problem. One Lee mould I had to loosen the plate so much, you would think it was too loose but it casts good boolits that way.

[Jim]

I'll copy and paste that to an email and send it to him. Thanks, Gear!

[MT Gianni]

Jim, I have a Lee mold that fills out one cavity well and the other has a base problem as well. It goes away if I fill the problem cavity first then the other second. It is an easy fix to do and I tape those instructions on the mold handle. [Fill back first!].

[grullaguy]

Geargnasher and Mooman76, you were dead on in my case. I loosened the sprue plate maybe a 16th of a turn and now I am again casting in both mold cavities. Thanks a bunch!

[Cap'n Morgan]

I decided to put venting lines on top of my molds since it was an easy thing to do while already fly-milling the top flat. As a result the base fill out improved. It's actually quite logic once you think about it; Even though you have fairly large sprue holes and keep distance to the nozzle when pouring, once the lead column reach the sprue plate, venting through the sprue hole will stop and if you're canting the mold ever so slightly, air will be trapped at the edge of the cavity. Loosening the sprue plate will help, but I believe it's a poor solution if you're anal about the weight of your boolits and the squareness of their base.

If you look at the pictures it's hard to believe, but with a loose sprue plate on this 458-450 mold, the pressure from the large "dead head" will actually lift the sprue plate from the mold - dead-head and all - creating fins on the base (and at the same time throwing the weight way off)

BTW: An easy way to went the top of a mold is to use a metal checkering file to put a row of thin hair lines across the top of the cavities.

http://img39.imageshack.us/img39/7470/img1144ih.jpg

http://img148.imageshack.us/img148/4717/img1146v.jpg

[docone31]

Your friend needs to heat the mold more. The 9mm is too small to heat soak the mold fast. The .45 will, but the 9 will not.
Just set the mold on the melt for a bit, prior to casting.
Use the six second rule. If the sprue freezes sooner, too cold. If the sprue freezes too slow, too hot.
The mold is too cool.

[MikeS]

Cap'n Morgan, why is the sprue on that mould so big? It almost looks like the sprues could be used as 12 ga. shotgun slugs!

[Cap'n Morgan]

Cap'n Morgan, why is the sprue on that mould so big? It almost looks like the sprues could be used as 12 ga. shotgun slugs!

It was an experiment to see if I could improve boolit uniformity by adding a "buffer" - It actually works great. I use a bottom pour pot with an enlarged spout hole and pour at full throttle until the sprue cavity is almost filled to the brim. By then the boolit cavity is about 1/2 to 3/4 full - then I just close the valve and let gravity do the rest. As a bonus it's much easier to avoid spilling :bigsmyl2:

[cbrick]

It almost looks like the sprues could be used as 12 ga. shotgun slugs!

Silly bullet caster. [smilie=s:

That's not what they look like to me. :groner:

Rick

[Lizard333]

Silly bullet caster. [smilie=s:

That's not what they look like to me. :groner:

Rick

I thought the same thing, when I first saw them......:redneck:
Always seeing them....Everywhere!!