View Full Version : A simple casting question...

05-18-2007, 10:06 AM
Thanks for all the input on the .45lc, now please allow me to pose a question 'bout casting if I may.
Like most of you, I have a small collection of molds I've acquired over the years. My favorites come from LBT, it seems almost impossible to cast a poor bullet with one of their molds if you do your part. Regardless of the mfg. though, I find if I drill the "pour" hole slightly larger (withing reason of course) I cast quicker and the mold fills out better with less rejects after the mold comes up to proper temp. Also, a small bevel on the top seems to allow the lead to flow smoother. This seems to be endemic to all the molds, regardless of mfg. and/or size. The only things I have to do is make sure the mold if full (and cold) before drilling, so the backside of the hole stays smooth and flush. Then I polish both sides and it works fine. Usually I can go 15%-20% oversize. And the spru is still cut flush.
This being the case (no pun intended) why don't the mfg's drill the holes larger to begin with? It's no big deal to drill oversize, and it's not rocket science to drill the hole in the centre, so why not save us the trouble? Maybe there's an industry standard for holes? Just curious. tnv

05-18-2007, 11:32 AM
The reason is simple--cost. They make scads of different sizes of molds and to tailor a different size sprue hole for every size boolit would make the molds more expensive or reduce profit. Some things need to be tweaked just like trigger pulls.

05-18-2007, 11:43 AM
So they only have to make one sprue plate design for a given cavity block size. Can you imagine how screwed up it could get if they had several different hole sizes for a given sprue plate. A 22-30 cal mold could not handle a SP with a hole size set up for a 458.

You also didn't say how you poured. Ladle or bottom pour? Makes a difference cause the stream sizes are different. With a ladel you can pressure pour or trickle it in. A ladle, pressure pouring, and a bottom pour can use a smaller hole.

I ladle pour and have modified a few SP's for a larger hole size. They do pour better, but it's highly mold and bullet dependent. Some like it hard and fast, some slow and easy. I've also opened up the ladle hole size for a faster pour on one of mine.

05-18-2007, 05:35 PM
I'm partial to bottom pours. Maybe I'm wrong, but it seems since the "garbage" float to the surface, the bottom is cleaner. I can also control the flow more easily. I've never had the bottom plug up on me, so maybe I've just been lucky so far. I've went thru three bottom pours in the last 25 years, so it could also just be what I comfortable with. Lastly, I seem to be clumsy (?) and have been known to spill a ladle or two of hot lead. tnv