Best way to align mold blocks

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John Alexander posted this 4 weeks ago

I have a mold that is out of alignment more than the usual -- approximately .002".  The bullets shoot pretty well as is but I can't help but think that it might shoot a mite better if the misalignment were a bit less.

Any advice, tips, etc. appreciated.

John

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RicinYakima posted this 4 weeks ago

Who made it? If a Lee, just throw it away as they are not adjustable. You may be able to do the better ones, but the problem is figuring out what is wrong. If the block were not square when cut with a cherry, they will never be fixable. But it one or more alignment pins / seats are off, you can some times fix those. Let us know.

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Ross Smith posted this 4 weeks ago

I'm with Ric. Is there something special about the mold? Can the problem be solved with sizing dies? I have some bullets that I run thru a sizer of the same size of the bullet just to make sure they are round. Lube sizer should also handle minor problems. Is this for a target rifle?

I have helped with mold alignment by cleaning the holes and making sure there was no lead around the pin or in the hole. It takes very little to keep the mold from closing properly and making funny bullets.

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OU812 posted this 4 weeks ago

I use a hydraulic press to push alignment pins in so they seat deeper in alignment holes. Sometimes the alignment holes wear larger and sometimes deeper pins can help realigne. Be sure to lube pin holes before use.

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OU812 posted this 4 weeks ago

You may be able to use a simple drill press as the press?

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OU812 posted this 4 weeks ago

Do the mould halves have any play when closed. One thing I always check when inspecting a new mould, does the mould close tight with no slop. Slop will increase over time if mould is used alot...especially Lyman moulds.

Sorry for having three separate post on this subject. I have not figured out how to edit old post.

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delmarskid posted this 4 weeks ago

I had to adjust the pins on a Lyman mold once. I think I placed the mold blocks together on the bench and moved the alignment pins with a punch and hammer. It wasn't a big deal.

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Bud Hyett posted this 4 weeks ago

This has happened before on a long-used mold. I have a RCBS 30-180-SP and Lyman 311384 with which I started casting 37 years ago.  

Steps I use in this situation:.

  • Disassemble the mold blocks, remove sprue plate.
  • Check that the mold blocks has not warped by seeing if light passes through the halves. 
  • Check all mating surfaces for burrs anywhere - deburr all edges.
  • Clean the interior mold surfaces very clean - Use bronze wool and almost burnish the surface. 
  • Check for any slight ridge around the female side of the alignment pin holes.
  • Very carefully flat file any ridge smooth using a fine flat Swiss file,
  • Put the mild halves together and tap the alignment pins with medium blows and a punch almost the size of the alignment pin. 
  • If the pins are loose and move, you will hear a slightly deeper sound when they seat in the other block. 
  • Check the percentage of contact in each hole using layout dye, or a Sharpie, to ascertain 90% contact in all holes.
  • Reassemble and cast sample bullets. 

If the problem persists, you may consider lapping the mold.  The lapping by default will give a slightly larger bullet.

Country boy from Illinois, living in the magical Pacific Northwest

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John Alexander posted this 4 weeks ago

Thanks to all for all the suggestions so far.

To answer your questions, this is a custom design in a custom mold, lathe bored by David Mos, a respected mold maker. For unmentionable reasons it can not be replaced. I have used the bullets in competition off and on for the last 20 years and it has produced tens of thousands of bullets. From time to time I have adjusted the protrusion of the alignment pins while checking progress with a mike but this doesn't seem to completely correct the mismatch.  The sizing die, of course makes the driving bands round.  I have also tried sizing the nose with an NOE nose sizing die.  This makes the nose round but doesn't improve groups and sometimes seems to make them worse.

After careful cleaning, I can't see light between the blocks or feel any motion.

I will working on it tomorrow and let you know if any progress.

John

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OU812 posted this 4 weeks ago

Maybe remove alignment pins and turning them 180 degrees then reinstall. Pins maybe worn more on one side.

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Geargnasher posted this 4 weeks ago

I fix the cherry- torque misalignment of Lyman 2C moulds using two strips of shim stock, a C-clamp, a 5" bench vise, and a small, flat-tipped punch. Clamp blocks together ther snug but not tight with the C-clamp, shim one mould half on opposite sides, squeeze in vise to shift blocks and pins/holes, and gently "fill in" metal on the loose side of the holes by judicial peening of block metal.

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