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Thread: Mold Tune-Up

  1. #1
    Boolit Master
    Join Date
    Apr 2006
    East TN

    Mold Tune-Up

    A while back I bought a used NEI aluminum 4-cavity mold. When the mold arrived I tried to cast some boolits with it but found that the block halves would not retain alignment. Most boolits the mold dropped were offset (side-to-side) and not round. Some were so far out of round they tried to prevent the blocks from opening to drop the boolits. Before casting I tried shaking the mold when pointed toward the floor, also when pointed toward the sky, to align the halves but this did not work. Out of frustration I set that mold aside to look at it again later. That "later" arrived today.

    I studied the block movement (no handles attached) and found the halves moved in a horizontal direction, but not vertical. This movement produced the misalignment that created boolits that were offset from side to side, but not top to bottom. The blocks have 3 indexing pins that align the sides. First I inspected the holes the alignment pins would enter, looking for any sign of excessive usage or out-of-round condition. All of the holes looked correct. Next I measured the length each pin was protruding from the face of the block they are installed in. The pins farther away from the end where I would mount the handles (sprue cutter bolt farther away from handles rather than closer) had shorter protrusion exposed to enter the opposite block. I measured each pin several times and recorded all these calls. I started with the farthest away (shortest pin) and moved it so it was .010" longer than the one closest to me (longest pin). Then I moved the center and rear pins to match the front pin and applied handles to the blocks. With these changes the halves open and close without resistance and alignment of the cavities is perfect. I installed handles and the mold halves open and close easily and maintain what appears to be correct alignment.

    So that's it. When the alignment pins didn't enter the opposite block deeply enough they failed to maintain alignment of the halves. By correcting their protrusion the block halves should perform as intended. Now it looks like I will crank up the furnace tomorrow and see if this project is finished.

    Side note - this mold makes wadcutter boolits for .32 revolver ammo. The design is a .313" diameter, button-top, bevel base wadcutter with a claimed weight of 105 grains. This is my only NEI mold so it holds a bit of history in my house. Here's hoping my Ruger Single Six 32 H&R Magnum will like them.

  2. #2
    Boolit Master

    Join Date
    Mar 2013
    Northwest Ohio
    Check the pins and make sure they are seating correctly. Some of the custom makers are now installing bushing in brass and aluminum moulds to slow wear of the alighnment holes by the pins. This wear can range from light to battering depending on how the mould is ran.

    I have a flat edge on the paint roller pan I use to drop bullets in. I rest the blocks on it when closing them to help pre alighn them.

    Steve Brooks site gives this tip. Use a small dead blow hammer for a sprue mallet ( 8 ounces or so, mine is a slimline head) use this for tapping the hinge pin and cutting sprue. close on the rail and lightly swing the sprue plate closed. I hook it with the back side of the mallets head. Then give the handle a couple light taps to seat the pins and make sure the blocks are seated. Not a blow but light taps to vibrated the blocks a little.

    The pins can be set as needed and need to be done first the above is to maintain not cure or correct.

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Abbreviations used in Reloading

BP Bronze Point IMR Improved Military Rifle PTD Pointed
BR Bench Rest M Magnum RN Round Nose
BT Boat Tail PL Power-Lokt SP Soft Point
C Compressed Charge PR Primer SPCL Soft Point "Core-Lokt"
HP Hollow Point PSPCL Pointed Soft Point "Core Lokt" C.O.L. Cartridge Overall Length
PSP Pointed Soft Point Spz Spitzer Point SBT Spitzer Boat Tail
LRN Lead Round Nose LWC Lead Wad Cutter LSWC Lead Semi Wad Cutter
GC Gas Check