Buildup of lead on mould

F

freebullet

Guest
I did remove some from the lube groove area on a couple brass molds. I used a tiny multilayer buffing wheel on a dremel. Used a very fine jewelry polish. I do that to most new lee molds too. Seems to make them drop easier.
 

James W. Miner

Active Member
I don't know if I mentioned this without reading the whole thread again.
I never get lead on mold faces but once in a while I get some under the sprue plate or mold top. I found if you strike a wooden match and blow it right out, you can rub the lead off with the ash on the head. I don't know why it works so well and the ash will crumble of course but as long as some is left, the lead cleans right off with no harm to the mold.
I run my pot at 750° and pre heat my molds to 500° for perfect first boolits. Proper timing for each pour will keep perfect boolits flowing.
Big brass molds need a little hotter. I never figured out why that is either.
I have made one mold where I can get whiskers so I made all the rest with .002" vent lines on one face only. I cut vent lines by advancing .025" and swinging a fly cutter by hand with a special cutter I ground. No more is needed. Then I break the top edges with a small file to vent the plate.
I always use an end mill to even the tops of the blocks before I cherry and I mill the sprue plate. I leave the end mill swirls for venting. By doing that my cavities are exactly 90° to the tops.
One other thing to do with a new mold is to round off all edges and polish them, more gouges are caused by plate edges then anything except lead buildup.
But never lap a plate or mold top, you can't make it flat, been there, did that and I wind up milling again.
Just deburr the pour hole.
Making my own molds has taught me so much I can run a 20# pot to the bottom without a reject. I ladle pour and when I can't get any more lead in it, I quit for the day. Of course I always did that anyway.
 

Pistolero

Well-Known Member
On iron molds with smears on the top, and underside of the sprue plate, I find that keeping a
small bit of BullPlate Lube on the parts will clear it up in perhaps 20-30 minutes of casting, it just
goes away. Not sure of the mechanism, but it has worked multiple times for me.

Bill
 

Bret4207

At the casting bench in the sky. RIP Bret.
Well, I'll add a couple thoughts. The biggest problems I have with sticking alloy on blocks is the top side of the blocks and bottom of sprue. A while back I was told that part of my problems soldering steel would be alleviated by rubbing the solder into the surface of the pieces to be joined with steel wool while the solder and surface were still hot. This would cause the parts to tin better. I think this may be the mechanism in play with my top side issues. It appears the same on alum moulds too. In either case, I still go back to 4/0 steel wool or a hardwood stick to remove the build up and then hit the area with the trusty old carpenters pencil. Buildup on faces has to come from not keeping the blocks thightly closed when pouring or opening a mould way too early IMO. I don't have much issue with that.

I own one brass mould IIRC, a Yankee, and it's an absolute joy to cast with. It doesn't seem to require any drastic heating or changes in pot temp. In fact, it tends to cast well with the mould seemingly cooler than I need iron or alum, but that's just a gut feeling since I have no easy way to check mould temps.
 

Kevin Stenberg

Well-Known Member
I don't remember what liquid it was. But I had small deposits in the mold gruves on a brass mold. And a repeated soaking and a scraping with a toothpick removed the deposit. It also removed the built up patina, which I had to redo.
This also taught me to take better notes on what I do!
 

Ricochet

Member
Another bad technique I tried that gave me this trouble was dropping bullets straight from the mould back into the pot when the mould is warming up and the bullets are not yet filling out properly. Also knocking sprues straight off into the pot. Molten lead splashes up onto the mould faces or top, and then you've got trouble. Took me longer than it should have to figure out that was a bad idea. I thought I was saving effort.
 

Cherokee

Medina, Ohio
Interesting reading, on the rare occasion of such a deposit, a swipe with a soft cloth on a hot mold seems to work for me.
 

Ricochet

Member
OK, I have extremely limited experience with brass molds. The only one I've used, and that just a little, is a copy of an ancient Colt mold that came in the presentation case with a Walker replica. I didn't have a problem with pure lead soldering to the brass, but I can see how that could happen especially with tinned alloy. I see how patina would help this. Has anyone tried artificially patinizing the cavities? There are all sorts of solutions to do this, from art stores or homemade. Lime sulfur from the garden store is said to work well. Zillions of recipes are online.