Lyman mold sprue plate

[hanover67]

I am about to start casting boolits and I have acquired several Lyman molds. One has some rust in the cavities which I am planning to treat with Evapo-Rust. Before I take it apart, I have a couple of questions about the sprue plate.
1) What is the set screw on the side of the mold for?
2) Once removed, how do you re-set the correct tension on the plate when re-installing it?

[Le Loup Solitaire]

Hi and welcome to the forum. The screw on the side of the block is for securing the bolt that holds the sprue plate down. It should have a little lead pellet or a brass one at the end to prevent it damaging the shaft of the screw/bolt that it secures. On tension for the sprue plate itself....Too loose or too tight is no good. The plate should just sit on the top of the blocks and swing free on its own weight when the blocks are tilted, with no slop up and down. Too tight will interfere with escape of air and cause incomplete fillout. It also can cause binding and galling of the plate against the tops of the blocks. When you have it set right then you tighten the screw on the side so that it stays put. Lube the underside of your plate with graphite...a carpenter's pencil works fine or else get some "Bullplate". Keeps things running smoothly and helps prevent any lead buildup/smears. LLS

[smoked turkey]

I will add that I have added a #8 lead shot under the set screw on several occasions and it also works to secure the sprue plate screw and also protects the threads. I have had to use pliers to flatten the shot down some in order to get the set screw started.

[hanover67]

Thanks for the advice. I have soaked the blocks in Evapo-Rust and most of the surface rust is gone. There is still some residual lead on the top of the blocks and the underside of the sprue plate. The inside of the cavities look like there is some pitting and I hope the boolits won't hang up when cast.

If I wipe down the cavities with kroil can I just let it burn off before casting, or do I need to claen it out with brake cleaner?

[Le Loup Solitaire]

I have never used Kroil although some folks use it. I just don't prefer to have oils, hydrocarbons or anything oily in my molds when I go to cast. I do store them that way but I use acetone- a soak and a scrub before preheating the blocks. Brake cleaner is a favorite cleaning agent of many casters. It works well. As for residual lead and/or lead smears on the tops of blocks and the underside of your sprue plate; it can be safely removed (as opposed to using a razor blade and scratching anything) by taking the corner of an ingot and rubbing the smear....the ingot will pick up the lead smear. it may take a little pressure/elbow grease, but it works! Burning anything off is always a possibility...it takes time and eventually works, but it also leaves a bit of residue. It is better to get anything that doesn't belong there to start with out of there-out of there, particularly the mold cavities, with something that does it cleanly. LLS

[shotman]

take the plate off and run it across a FINE stone. do the same to top of mold.
AND as most know here get Kroil LOL