lousy results w/alum mould..??

[FN in MT]

I can warm up ANY of my steel Lymans and in short order I'm producing nice boolits. Not filling out? Gently degrease, carefully dry, then smoke it with a match...generally gets things running again. Frosting slugs? I'm casting too quickly and/or I've let the alloy get too hot. I can generally think through a problem.

NOT so with ONE of my pair of old NEI aluminum Keith style two holers. Despite degreasing and smoking the blocks the .411" mould refuses to drop a decent slug. It pours rounded edges or the bases not filled out. Occasionally it drops a few decent slugs buy thats maybe 3 or 4 out of ten!!

It's pack mate a .451" is the exact opposite. One can't barely make it drop a bad slug. Within four or five quick fills of start up .......it's dropping well filled out slugs.

WHATS the key to making a problem aluminum mould drop a good slug?? What temp should my alloy be?? I've tried cleaning with carb cleaner, degreasing solvent, HOT water with simple green and it appears CLEAN.

I'm stumped.

FN in MT

[HeavyMetal]

Some suggestions:

Check the hole in the sprue plate on both the NEI molds, make sure they are the same size.

If that checks out: increase melt temp, try a 50 Degree bump.

OR:

Check alloy, if your using straight WW metal add some tin but no more than 2% per volume of the pot!

Dip a corner of the mold in the alloy untill it hot enough that the metal does not stick to it!

One or all of these suggestion might be the right ticket.

[Springfield]

Sometimes I get a LEE 6 cav mould that has 1 or 2 cavities that just won't drop well filled bullets. I have found that opening up the sprue hole works wonders. I assume it is a venting problem but this has always been an easy fix and doesn't affect the bullet. I prefer it to touching the mould edges with a file to improve venting as that is an irreversable fix and may not work as well anyway.

[pjh421]

After all that cleaning its definitely a venting problem. Look at your vent lines under magnification. I've had good luck using a carbide scribe, lightly. When the mould is not venting some of these grooves may have peened over and closed enough to trap air around your casting.

Paul

[shotman]

I go with venting also. Ever look at a LBT mold? I have never seen a bad boolit come out of one

[Bret4207]

Turn up the heat and cast faster.

[moto357]

I have an NEI single that gave me the same results, 30 fast drops to get it hot with no luck, pot much hotter than I prefer and the same. Anyways, lots of playing with no change up until I lightly scribbed the vent lines. It's still the pickiest mold I have, but once it gets going nicely I slow the pace and the "keepers" drop one after another... so my vote goes with the others that it sounds like a venting thing

[FN in MT]

Venting IS about the only thing I've not checked. I'll get back to You guys later today.

FN in MT

[Larry Gibson]

Concur with Bret4207; turn up heat and cast faster. Also try it without smoking the cavities. The aluminum moulds cool much faster than iron ones. If you are not casting fast enough with a hot enough alloy the problems you describe arrise. If you are using a bottom poor furnace and can adjust the flow rate open it up some. On larger fatter cavities it is necessary to get the alloy into the mould as quick as possible. Opening up the sprue hole does the same thing.

Larry Gibson

[montana_charlie]

Make sure the sprue plate is not too tight...

[Maven]

One more point: Sometimes Al molds don't respond well to smoking. My Lee molds all do, but only 1/2 of my LBT's prefer it. Btw, I agree with the looser sprue plate and higher melt temps. (800 deg. F to start) as well.

[FN in MT]

I carefully ran a scribe over the vent lines on the .41 mould. Recleaned it , heated it and did NOT smoke it. Withing thirty or so tries I was turning out TWO good slugs!!! Well filled out and dropping out of the mould with very little urging.

But I have to say.....my lone LEE 6 cavity, also a .41 SWC... likes to be smoked.

There's SO MUCH experience here! So nice to have a problem....post it.....in no time a guy has THE solution.

Thank's for the solution Gentlemen!!

FN in MT

[Dan Cash]

I have seen a sprue plate on some custom mold that had a slot cut out from the sprue hole to improve venting on big BP bullets. Not having this brand mold and hesitating to cut the plate on my mold, I cut a slot in the edge of my ladle nozzle. That and reaming the hole to 3/16 inch really made a difference. I pour about half a dipper of melt for each bullet, letting the excess run back into the pot. Things fill out nicely. It works for me with Hoch, Lyman, LBT and lee.