Ordered My First MiHec Mold!

[Phlier]

I guarantee there is no zinc in the alloy.

[Phlier]

I keep a rag with a little 2 cycle oil on it when casting. When I start casting, with the cavities full, I will wipe the top of the mold, bottom and top of sprue plate. This will stop lead from sticking. I do this occasionally during the casting session and anytime I get lead on the top of the mold. Don’t use a lot of oil just enough so the rag feels a little wet.

I'll give that a try, thanks for the suggestion. That sounds like it would be a lot faster (less mold cooling) than going over the areas with pencil graphite.

I only own around ten molds, but I've never had this problem before with any of them.

[Wheelguns 1961]

I do it with all my molds.

[OS OK]

This was my first brass mould also...so...I thought I might go full 'OCD' preparing the mould for service.

I boiled it with dish soap...brought it to a roaring boil and let it go for 15 minutes 2 times with soapy water, then boiled a third time with fresh water.
Each time refilling the pot under the faucet and allowing the cutting oils to flow out over the top of the pan...

After that I heat cycled it 3 times in the oven...

Then when it was cool, I lubed it up as I assembled the pins in the order I want, put powdered graphite on them and rubbed it into the pins well and put it back in a different oven to preheat to 350ºf for casting...

No smoke in the cavities...no mould release...no magic....hmmmm, but you do have to hold your mouth just right!

[Phlier]

OS OK, love it!

My new mold is aluminum, but only because it wasn’t offered in brass or steel. I can imagine an 8 cavity mold made out of brass would be darn heavy for my old arms.

I also did a very thorough cleaning, but not quite to that level.

I sure hope my little issue isn’t coming across as a complaint. That’s not my intention at all. The quality of workmanship on this mold is jaw dropping. I thought the old Lyman 42943(?)1 mold that my Dad gave me was fantastic quality. And it is. But words just don’t do justice to describe the level of craftsmanship Miha puts into his molds; you just gotta see one in person to really appreciate it.

I really appreciate the help, suggestions and info you guys have provided. I thought that I had ran into every problem a guy could have while casting boolits, but apparently not, as I’d never had sprues get welded to a sprue plate before.

[OS OK]

I wish that I could tell you exactly what caused the welding but have no idea other than something in the pores of the metal that didn't come out when you cleaned it. I think as our moulds get used over and over again, they form a microscopic carbon patina in the cavities and on the top of the sprue that won't allow the lead to cling to the surface of the metal...other than that guess, I have no idea.

No matter how long you cast you'll always come up against something that'll make you scratch your head?

[Petander]

I guarantee there is no zinc in the alloy.

Sometimes my Mihec sprue plate looks like that.

But it never became a welding/sticking problem. I thought those traces came from cutting a tad early.

I like your "full pot at once heat cycle" - method, Sir Bird.

[Phlier]

No matter how long you cast you'll always come up against something that'll make you scratch your head?

Sure seems that way.

The wife said I could have this evening to cast, so in a couple hours from now, I'm planning on sitting at the casting bench until the wee hours of the morning working on this. Hopefully I'll get a couple thousand keepers along the way, even if the sprue issue isn't solved along the way.

[Phlier]

Sometimes my Mihec sprue plate looks like that.

But it never became a welding/sticking problem. I thought those traces came from cutting a tad early.

I'll try tacking on some additional time and see if it helps... I did try adding a bit of extra time, but didn't want to lose the mold's "sweet spot" temperature.

I like your "full pot at once heat cycle" - method, Sir Bird.

Throwing 8 boolits at a time, that full pot goes quick!

[Phlier]

Well, gents, using Wheelguns 1961's suggestion, I was able to keep the pot running all night. Every once in a while, the sprue would start to weld to the sprue plate again, and a quick (and very thin) swipe of mold lube oil on the plate solved (or at least covered up) the issue. I was concerned that using oil right where the alloy flows would result in wrinkled boolits, but it turns out that they weren't affected at all.

The new mold is dropping perfect little boolits that need very little persuasion to drop out. Ended up with about 2.5k of 'em. Today they'll get PC'd, sized (my son isn't going to get out of sizing duty today ), and loaded.

[Phlier]

Just a quick follow up...

So I've run about 50 lbs of alloy through my new MP mold... yeah, I've spent more hours with this mold in the last week than I would really care to admit.

Starting about ten lbs of alloy ago, I stopped having the problem of sprues becoming welded to the top plate. I still have no idea why it did it in the first place, but now for some reason it has completely stopped being an issue. The only problem I have is that occasionally I won't get completely perfect bases, but that's only when the mold cools off to just below the perfect temperature. This mold has a very narrow operating temperature window, and I have to maintain a perfect cadence. But as long as I *do* maintain that perfect cadence the boolits are just wonderful.

The mold didn't start casting *really* well until it had about five full temperature cycles on it. So my advice to anyone looking at getting an 8 cavity aluminum mold from MP would be to do at least three full heat cycles (from room temp up to 375F-400F, hold for 15 minutes, allow to cool to room temp) before casting with it.

I'm really looking forward to acquiring more of Miha's art work.

[baragasam]

His shop definitely puts out great molds. I personally have a brass 4 cav 147gr HP 9mm mold from him. Casted couple thousand bullets with no issues at all. Just need to make sure the mold is prepped and taken care of afterwards.

[Petander]

Just need to make sure the mold is prepped and taken care of afterwards.

What do you do to a MP brass mold afterwards?

Now in winter it's very dry here,I put my molds on a shelf. Do nothing to them. Heat them up and lube for the next session. No oil,no bags,boxes,no cleaning (I don't smoke).