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Sprue plate lube (Read 485 times)

cellargun Full Member Offline Posts: 115 Joined: Feb 28^th, 2022	Sprue plate lube Jan 4^th, 2026 at 7:36pm	Print Post
	What do you use to lube the sprue plate? I've tried bullet lube, 2 stroke premix oil, paraffin, magic sprue plate lube sticks from LBT, and probably something I can't think of. Every time I think something works, it migrates into the cavity to trash any bullets cast till I scrub off every trace of the lube, then it's back to dragging dryly, or worse, galling. Mold material doesn't seem to make a lot of difference, although iron blocks seem to be the least affected.


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westerner Frequent Elocutionist Offline deleted posts and threads record holder. Posts: 12105 Location: Why, out West of course Joined: May 29^th, 2006	Re: Sprue plate lube Reply #1 - Jan 4^th, 2026 at 7:44pm	Print Post
	Soapstone or nothing at all. Lead will not stick to soapstone, also it will not contaminate your mold cavity. It will not smoke or burn. Best thing since peanut butter. Been using it for forty years or more. Apply it to the sprue hole, under the sprue plate and on top of the mold blocks. Soapstone acts as a lubricant. Soapstone is cheap and lasts a long long time. It can be used to play hopscotch. Can use it for laying out and marking steel projects. Did I miss anything? Oh, I use it to powder my bags when shooting from the bench.
	« Last Edit: Jan 4^th, 2026 at 7:54pm by westerner »
	A blind squirrel runs into a tree every once in a while.
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art_ruggiero Frequent Elocutionist Offline Posts: 1200 Location: CT Joined: Dec 14^th, 2008	Re: Sprue plate lube Reply #2 - Jan 4^th, 2026 at 7:48pm	Print Post
	powdered graphite apply to mold blocks with a bullet in the cavity


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Smoke Oldtimer Offline Posts: 819 Location: San Diego Joined: Feb 24^th, 2013	Re: Sprue plate lube Reply #3 - Jan 4^th, 2026 at 7:51pm	Print Post
	Rapine Mold Prep. It's graphite based, so it lubes. It dries and keeps lead and other stuff from sticking to the mold surfaces. I don't use it in the cavity but I spread it liberally around the top of the mold, and all sides of the sprue plate.

	I've never really trusted Smokey the Bear. Everytime I see him I wonder what happened to the Boy Scout that was orginally wearing that hat.
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rgchristensen Frequent Elocutionist Offline Posts: 1169 Joined: Jan 2^nd, 2014	Re: Sprue plate lube Reply #4 - Jan 4^th, 2026 at 8:01pm	Print Post
	I’ve never had any reason to lube a sprue plate. Maybe running the mould too hot? Or an unsuitable alloy? I stick with pure lead and tin. CHRIS


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bpjack Frequent Elocutionist Offline Posts: 3569 Location: East Olympia, WA Joined: May 18^th, 2008	Re: Sprue plate lube Reply #5 - Jan 4^th, 2026 at 8:06pm	Print Post
	Messy, but easy. I touch a cheap birthday cake candle (the cheap ones I use to smoke the cavities) to the plate screw WITH a hot bullet in the cavity. Don't over do it.

	ASSRA # 11318 Experience is something you don't get until just after you need it.
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Oleblacksmith Junior Member Offline Posts: 58 Joined: Jan 10^th, 2024	Re: Sprue plate lube Reply #6 - Jan 5^th, 2026 at 7:30am	Print Post
	cellargun wrote on Jan 4^th, 2026 at 7:36pm: What do you use to lube the sprue plate? I've tried bullet lube, 2 stroke premix oil, paraffin, magic sprue plate lube sticks from LBT, and probably something I can't think of. Every time I think something works, it migrates into the cavity to trash any bullets cast till I scrub off every trace of the lube, then it's back to dragging dryly, or worse, galling. Mold material doesn't seem to make a lot of difference, although iron blocks seem to be the least affected. I don't understand. I have never had the problem you are describing in more than 50 years of bullet casting. The only thing I can imagine is that you are tightening down the sprue plate too much. The sprue plate should swing freely and you use the dipper to push the plate down to the top of the mold to hold it in place and keep the lead from spreading.


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Bent_Ramrod Frequent Elocutionist Offline Posts: 1553 Location: Southern Arizona Joined: Feb 8^th, 2006	Re: Sprue plate lube Reply #7 - Jan 5^th, 2026 at 8:15am	Print Post
	As long as your lead is clean and you're using iron moulds, sprue plate lube shouldn't be needed. However, aluminum moulds with steel sprue plates will gall if you look at them crosseyed. I usually smoke the cavities of those anyway to retard heat loss in casting, so some of the soot on top of the mould and bottom of the plate, and a judicious touch of wax as bpjack describes, is perfectly in order.


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silver Full Member Offline Posts: 229 Location: Central wi, Joined: Sep 20^th, 2016	Re: Sprue plate lube Reply #8 - Jan 5^th, 2026 at 8:55am	Print Post
	I just touch the mold at the pivot point with a pcs. Of parafin wax. After every 25 or so bullets if it’s needed.


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cellargun Full Member Offline Posts: 115 Joined: Feb 28^th, 2022	Re: Sprue plate lube Reply #9 - Jan 5^th, 2026 at 9:30am	Print Post
	Thanks everyone. I like the idea of something dry. Graphite came to mind at some point, but soapstone is a new one. As stated, I've tried some paraffin based lubes with generally poor luck. The troublesome mold yesterday was a Hoch with double sprue plates that was no doubt too snug at the pivot. Lesson learned the hard way, as usual. Iron are most forgiving, followed by steel, then aluminum. Can't comment on brass since I don't have any.


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calledflyer Frequent Elocutionist Offline Posts: 3871 Joined: Mar 9^th, 2015	Re: Sprue plate lube Reply #10 - Jan 5^th, 2026 at 10:09am	Print Post
	I keep an old carpenter's pencil with me when casting. I 'write' on the block faces, top and bottom of the sprue plate. A tiny dab (really tiny) of parafin on the screw once in a while. Ol' Harry stamped ''wax'' on his molds and it's the one thing he taught me that is universally good advice.


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Jonathan Participating Member Offline Posts: 40 Location: THE GOOD PART OF NY Joined: Sep 5^th, 2025	Re: Sprue plate lube Reply #11 - Jan 5^th, 2026 at 10:39am	Print Post
	I've been casting bullets for a long, long, time and have had to tighten up a sprue plate now and then but never had to lube one.


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marlinguy Frequent Elocutionist Offline Ballards may be weaker, but they sure are neater! Posts: 17521 Location: Oregon Joined: Feb 2^nd, 2009	Re: Sprue plate lube Reply #12 - Jan 5^th, 2026 at 2:45pm	Print Post
	I have a few aluminum NEI and NOE molds, and the first thing I do before using them is to remove the sprue plate and lay the bottom side on some 500 grit paper and polish it until it looks like a chrome bumper. That usually helps them from ever galling. I've done the same to some steel molds also that had issues not working smoothly, and added some powdered graphite at the same time.

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westerner Frequent Elocutionist Offline deleted posts and threads record holder. Posts: 12105 Location: Why, out West of course Joined: May 29^th, 2006	Re: Sprue plate lube Reply #13 - Jan 5^th, 2026 at 3:28pm	Print Post
	cellargun wrote on Jan 5^th, 2026 at 9:30am: Thanks everyone. I like the idea of something dry. Graphite came to mind at some point, but soapstone is a new one. As stated, I've tried some paraffin based lubes with generally poor luck. The troublesome mold yesterday was a Hoch with double sprue plates that was no doubt too snug at the pivot. Lesson learned the hard way, as usual. Iron are most forgiving, followed by steel, then aluminum. Can't comment on brass since I don't have any. They can be pesky. Clearance changes as they warm up. On one Hoch mold I finally made a new spacer for it, problem solved. As to soapstone, I use it to stop lead from sticking to the mold surfaces. When I'm casting and bullets are flying out of the mold like popcorn, I'm liable to smear a little lead once in a while.

	A blind squirrel runs into a tree every once in a while.
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Spud Oldtimer Offline Posts: 522 Location: Australia Oz Joined: Feb 24^th, 2005	Re: Sprue plate lube Reply #14 - Jan 5^th, 2026 at 6:30pm	Print Post
	Westerner, What's soapstone? Is it a natural product? Spud


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