This is a short excerpt from "Cast Bullets for Beginners & Experts" was written by Ken Mollohan.
This has mostly to do with Lyman and other iron/steel molds with Lyman-style alignment pins. I know little about maintaining aluminum or brass molds.
Any trace of oil or grease on a mold will smoke and cause severe wrinkling of the bullets. Consequently, all molds must be clean and dry before use. Some casters never put any preservatives on their molds: they just leave the last bullet cast in its cavity as a sort of protection. I know one fellow who stores the dry molds in a box of heavily galvanized steel. It seems to work, but most of us are more comfortable with some sort of petroleum based rust inhibitor for safe storage. Which means it must be removed before the mold is used again.
I’ve used every solvent you can think of, and probably quite a few you never even heard of, trying to get the metal really clean. Some shooters clean their molds with soapy water and a brush and report good results. But the best way I’ve found was recommended in the American rifleman some years ago. They suggested bringing a sauce pan with 2 or 3 inches of water to a rolling boil, and adding ‘some’ dish detergent - maybe half a teaspoon if you just HAVE to measure it. Then open the mold (on handles) and set the blocks in the pan. The water should cover the blocks. Then let the pan come back to a rolling boil. You’d think this is going to boil over and make a mess, but it doesn’t. Let it boil for about a minute. Then take it out and rinse it off briefly in scalding hot tap water, and sling it dry. Be very careful not to give it a long rinse with cold water: The metal will be so free from oils that if it’s kept wet, it will rust in a hurry! But a hot mold will dry quickly, and will give you no trouble with rusting. This takes only a few minutes, and is the best method I’ve found.
Bullet molds need to be adjusted now and again because they wear and get damaged. Sometimes the mold doesn't close completely, sometimes the mold halves will move when the mold is closed, and sometimes the sprue plate isn't flat or has bumps.
There must be no lead on the face of either half of the mold. Get the lead off by heating the mold and touching the lead with the tiniest bit of bullet lube. The lead will go away as you cast. Ken's method is to heat the mold so hot the lead specks melt. -Then wipe the molten lead away with a slightly oily rag after you’re done casting, so it will be clean for your next session.
With the mold off the handles, check as follows: Hold the closed mold up to the light, look through the bullet cavity, and see if there's light coming through a crack. Any visible light means that the mold isn't closing completely. Hold the closed mold in two hands, one hand holding each half, and see if the halves move when you try to twist them. The slightest movement can be easily felt. If the mould fails either test it should be adjusted for the best results. Remove the sprue plate and screw and washer from off the mould half. You'll need a small fine file. My file is eight inches long. A file with a "safe" edge, with no teeth on the edges, is preferred.
This has mostly to do with Lyman and other iron/steel molds with Lyman-style alignment pins. I know little about maintaining aluminum or brass molds.
Any trace of oil or grease on a mold will smoke and cause severe wrinkling of the bullets. Consequently, all molds must be clean and dry before use. Some casters never put any preservatives on their molds: they just leave the last bullet cast in its cavity as a sort of protection. I know one fellow who stores the dry molds in a box of heavily galvanized steel. It seems to work, but most of us are more comfortable with some sort of petroleum based rust inhibitor for safe storage. Which means it must be removed before the mold is used again.
I’ve used every solvent you can think of, and probably quite a few you never even heard of, trying to get the metal really clean. Some shooters clean their molds with soapy water and a brush and report good results. But the best way I’ve found was recommended in the American rifleman some years ago. They suggested bringing a sauce pan with 2 or 3 inches of water to a rolling boil, and adding ‘some’ dish detergent - maybe half a teaspoon if you just HAVE to measure it. Then open the mold (on handles) and set the blocks in the pan. The water should cover the blocks. Then let the pan come back to a rolling boil. You’d think this is going to boil over and make a mess, but it doesn’t. Let it boil for about a minute. Then take it out and rinse it off briefly in scalding hot tap water, and sling it dry. Be very careful not to give it a long rinse with cold water: The metal will be so free from oils that if it’s kept wet, it will rust in a hurry! But a hot mold will dry quickly, and will give you no trouble with rusting. This takes only a few minutes, and is the best method I’ve found.
Bullet molds need to be adjusted now and again because they wear and get damaged. Sometimes the mold doesn't close completely, sometimes the mold halves will move when the mold is closed, and sometimes the sprue plate isn't flat or has bumps.
There must be no lead on the face of either half of the mold. Get the lead off by heating the mold and touching the lead with the tiniest bit of bullet lube. The lead will go away as you cast. Ken's method is to heat the mold so hot the lead specks melt. -Then wipe the molten lead away with a slightly oily rag after you’re done casting, so it will be clean for your next session.
With the mold off the handles, check as follows: Hold the closed mold up to the light, look through the bullet cavity, and see if there's light coming through a crack. Any visible light means that the mold isn't closing completely. Hold the closed mold in two hands, one hand holding each half, and see if the halves move when you try to twist them. The slightest movement can be easily felt. If the mould fails either test it should be adjusted for the best results. Remove the sprue plate and screw and washer from off the mould half. You'll need a small fine file. My file is eight inches long. A file with a "safe" edge, with no teeth on the edges, is preferred.
Here's a picture of the file and the mold that we'll use for an example. On the mold half with the alignment pin holes (the half without the pins sticking out), hold the file flat on the surface of the mould and lightly file off any metal that projects above the surface. We're not taking much metal off. We just want to take off the bumps and make the surface flat. You will be able to feel the file take off metal, and you'll feel it when the file is done taking off metal. The alignment pin holes on a used mold are almost always burred
Here's a picture of that mold half after filing, the bottom alignment pin hole clearly shows the white ring left after the burr was filed off, the top hole looks the same but didn't photograph as clearly.
Now file the face of the other mold half-the half with the alignment pins sticking out-, being careful not to file any metal off of the alignment pins.
Now file the face of the other mold half-the half with the alignment pins sticking out-, being careful not to file any metal off of the alignment pins.
Here's where having a file with a "safe" edge, with no teeth, is helpful. Just be careful not to remove metal from the alignment pins. File off any bumps at the edges of the mold half. When it's flat, stop. Less filing is better.
To keep the alignment pin holes from burring again, get out your chamfering tool, or cricket, and chamfer the inside of the
To keep the alignment pin holes from burring again, get out your chamfering tool, or cricket, and chamfer the inside of the
alignment pin holes-just a little bit! Above is the mold half and the cricket: (NEI and RCBS moulds come with the alignment pin holes chamfered, Lyman molds don't.)
Before you adjust the alignment pins, make sure that the mold half faces are flat and burr-free as explained above. These steps must be done in the proper order.
Before you adjust the alignment pins, make sure that the mold half faces are flat and burr-free as explained above. These steps must be done in the proper order.
Adjusting the alignment pins:
If you can feel movement when holding the mold halves closed in your hands-when twisting them-the alignment pins need to be adjusted. You will be able to feel which alignment pin is loose. Just fiddle with the mold for a while, twisting the halves in your hands. You can feel the slightest movement.
I use a punch, a hammer and a lead alloy ingot to adjust the alignment pins. Put the closed mold on the ingot and tap the punch on the alignment pin with the hammer.
If you can feel movement when holding the mold halves closed in your hands-when twisting them-the alignment pins need to be adjusted. You will be able to feel which alignment pin is loose. Just fiddle with the mold for a while, twisting the halves in your hands. You can feel the slightest movement.
I use a punch, a hammer and a lead alloy ingot to adjust the alignment pins. Put the closed mold on the ingot and tap the punch on the alignment pin with the hammer.
It may take several whacks, maybe a hard whack. Eventually the pin will move. If the pin has gone out too far, so that the mold halves stick together when closed, then just tap the pin back into the mold half with the hammer. The goal is to have no movement of the two mold halves and no sticking when the mold is closed. (Some shooters adjust the alignment pins with an arrangement of ball bearings, shims, and a vise. I've never tried it.)
Filing the sprue plate flat. Sometimes the sprue plate gets bumps and uneven surfaces and lumps at the outside edges. The sprue plate must be flat. File the bottom of the sprue plate until all the bumps are gone, and it is flat.
Filing the mold top. The top of the mold sometimes gets burrs at the edges and around the sprue plate hole. ONLY after the mold half faces are filed flat and the alignment pins are adjusted, file off any burrs on the top of the mold.
Filing chamfers on mould edges Some folks also file a chamfer on all four edges of the mating surfaces of both mould blocks; to make sure that no burrs will be raised to keep the blocks from closing completely.
Filing chamfers on mould edges Some folks also file a chamfer on all four edges of the mating surfaces of both mould blocks; to make sure that no burrs will be raised to keep the blocks from closing completely.