First casting - monkey is off my back!

[Worn_Holster]

Casting with a new Miha 434-256... my casts looked pretty good except the very top of the cast's edge under the sprue was rounded, not a nice sharp edge. Was I not casting hot enough?

[gray wolf]

Sprue plate to loose/ to tight--should swing freely
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screw on other end has a large head, it should allow the plate to lift a little, both screws are influential.
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Try pouring the metal directly into the center of the sprue plate hole if bottom pour pot is used.
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Metal may be to cool, you didn't say the temp.
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how are the rest of the boolets looking ?

my casts looked pretty good What does pretty good mean ?
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What do you use to pour the lead ladle or bottom pour ?
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what is the distance from spout to mold ?
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Are you hitting the edge of the sprue hole or going directly into the center ?
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If bottom pouring pot, try the metal at 700* and go directly into the center of the hole
That is what cured it for me.

[JonB_in_Glencoe]

WH,
if that new Miha mold is brass and that's your first brass mold, then you just learned that brass molds need to be run hotter than alum or iron molds.
Good Luck,
Jon

[Worn_Holster]

I don't know what temp, Lee pot only has numbers, set it at 6...
What does pretty good mean ?
--- Completely filled, but ripple lines visible on some boolits
What do you use to pour the lead ladle or bottom pour ?
--- Ladle pour
what is the distance from spout to mold ? I set the ladle spout lip at center of hole, mold held at 45 degrees, then turned ladle and mold together until mold sprue was horizontal.
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Are you hitting the edge of the sprue hole or going directly into the center ? Center

[Iron Mike Golf]

Worn Holster,

Get a BBQ grill thermometer that goes up to 800 or 900 degrees. When pouring that mold, I run my melt at 675-700 deg. My alloy is 92-4-4.

Are you using a hotplate to pre-heat your mold? The edge of the pot might not get your mold hot enough. Are you pouring a puddle on top of the sprue plate after filling the cavities? Think of that as adding heat to the mold to keep it up to temp.

In addition to the tightness of the sprue plate, you can also assist base venting by breaking the top edge of the mold blocks where they meet one another. A few strokes against either a fine diamond stone or 400 grit wet/dry sandpaper backed by a flat surface (1/4 inch plate glass, for example) will create a nice vent line at the very top of the mold blocks.

[Worn_Holster]

If I had to make a guess, I'd say that my mold was not hot enough. I'll get a hotplate to pre-heat with; any suggestions of what kind works best?

[RobS]

I think you are right........mold a bit cool. Any hotplate that has a solid top to it, not the coil type, will work fine. I have a wal-mart GE that I found on sale for around $10.

If you still have issues after increasing the mold temp and adjusting the sprue plate to a bit looser fit I would say there is a venting issue and an easy fix is to just break the edge of the inside, top of the mold where the blocks come together. I typically do this by taking the mold off the handles and position half a block at a 45 degree angle and run it across a few times on a 320 grit dry/wet sand paper that is laid on a flat surface. Repeat for the other half of the mold.

[Worn_Holster]

OK, I got a hot plate and my cast are coming out completely filled, but I have changed something about how I am casting which I don't understand. My first time, all my casts we nice smooth and shiny, but this time the boolits are frosty looking. Does someone have an explanation of what I am doing incorrectly? Thank you!

[ultramag]

Frosty is an indicator of too hot....most likely your mold. A little frost doesn't seem to hurt anything. If it bothers you or the frosting gets excessive cast slower and it should correct itself.