Finning/Tinning

[ColColt]

Got my favorite 45 cal mould(457125) out a couple hours ago waiting on a pot of 1:20 to melt while the mould heated. I got through about 75 good looking bullets and starting seeing fins on both sides of the bullets. I opened the mould and the culprit was the alloy adhering to the vents and top of one half of the bullet...session over.

I put some bees wax on the mould and tried picking it out with a toothpick very carefully while still hot but had little success. I know this has been discussed before as I was in on it about a year ago. What's causing this? I let the mould cool down and will try to pick out the tin once it's cooled. Best I recall, this is the first time this mould has done this. I had it happen with a brass mould but to my recollection never with an iron one.

[burrkiss]

Sounds like this was the same problem I had a few days ago. Take your mold apart; clean it properly, relube the bendy bits, re smoke it. Make sure you check the sprue plate bolt for lead underneath.

[williamwaco]

Are you talking about the "whiskers" that form in the vent lines?

You can wipe them off with your finger.

[ColColt]

You won't wipe these off with your finger. The tin, I assume that's it, is embedded in the vent lines just at the edge on both blocks. Not all of them but enough to cause problems. I think I know whey it started but not sure. As I was casting one of the screws fell out of one of the blocks..the bottom one that holds it to the handles. I didn't notice it and may have not got closed the mold completely allowing the alloy to get to the inside area just a bit. I've worked on those blocks for nearly an hour, heating them back up, applying bees wax, taking a tooth pic and wooden paint stirrer and all of it is just not coming off.

the bullet, yes-the whiskers can be wiped off but not from the mould.

[williamwaco]

You won't wipe these off with your finger. The tin, I assume that's it, is embedded in the vent lines just at the edge on both blocks. Not all of them but enough to cause problems. I think I know whey it started but not sure. As I was casting one of the screws fell out of one of the blocks..the bottom one that holds it to the handles. I didn't notice it and may have not got closed the mold completely allowing the alloy to get to the inside area just a bit. I've worked on those blocks for nearly an hour, heating them back up, applying bees wax, taking a tooth pic and wooden paint stirrer and all of it is just not coming off.

the bullet, yes-the whiskers can be wiped off but not from the mould.

I have occasionally removed alloy from the face of a block by heating the block with a propane torch until the alloy melted then wiping it off with a very coarse cloth like duck or burlap.

[John Boy]

... and starting seeing fins on both sides of the bullets.

My guess is either the block pins were not lubed at the start of the casting session or the pins needed to be relubed

Removing the alloy in the vent lines ... wipe the blocks with a piece of leather or lead remover cloth

[Dan Cash]

In all my years of casting, I have yet to have a mould get so lead smeared that the offending material could not be wiped away. However, should the situation arise, I suspect that a solder wick such as Tech Spray brand Prow Wick, a woven copper cable used to suck solder from electrical connections would get the job done. One would heat the mould until the lead melted and touch the leaded spots with this copper wick. As the wick gets hot, the lead would migrate to the wick. I have not done this as the need has not presented itself but worth a try.

[ColColt]

I finally got it all off and decided to start another session to see if the problem would resurface. It didn't. I did lube the pins with what little Bull Plate I have left but initially I don't remember if I did or not. When material, be it tin or whatever, gets right at the edges of the cavity between the vent lines it's hard to get off. I was leery of heating it with a torch for fear of warping the block. I did have a speck or two I couldn't remove but apparently it melted off during the last casting session.

[John Boy]

I did lube the pins with what little Bull Plate I have left but initially I don't remember if I did or not.

I believe you didn't.
Put this in your bag of casting tricks ... Paraffin, an alkane!
* Use to lube pins
* Sticking lead because it smeared not letting the sprue to harden - wipe top of blocks, bottom of plate and sprue hole. You'll be amazed how fast the sprue puddle slids off the plate when you cut it
* Fins ... wipe vent line with paraffin. Next couple of bullets will have dimples but after that - good bullets

[ColColt]

You're probably right about lubing the pins...usually I do but in all actuality I didn't this time, apparently. I use a bit of Bull Plate on a q-tip to lube the pins normally and on top and bottom of the sprue plate and block. I've never rubbed paraffin or bees wax on the vent lines. I'll give that a stab next session.