Mould re-conditioning ?

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Last Post 02 March 2025

CBA Member

Slug Gun posted this 01 March 2025

Is there such a thing as mould block re-conditioning, I have two steel Lyman moulds that could use some work.

If so, do you know of anyone that does this ? There contact information please.

Thanks……Gary

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CBA Member

fc60 posted this 02 March 2025

Greetings,

I do it quite a bit.

Remove sprue plate and all screws.

Drive out the two locating pins. (Remember which mould block they came from.)

With a stone of fine cut file, remove all the burrs.

Source a 90 degree countersink and chamfer the locating holes. Also, knock the sharp edges from all the other holes.

Visit the autobody supply shop and buy a few sheets of 600 wet/dry paper.

Cut a small piece of paper and place in on a flat surface (glass or metal) apply some alcohol, Windex, or Kerosene to the paper and carefully clean the faces with the cavities. Notice a bright ring around the index holes. Clean carefully as you only want to remove the crud/burrs.

Clean the blocks and insert the locating pins.

Tap one pin only until the mating block starts to stick. Stop here.

Do the same with the other locating hole.

Assemble the blocks and "tap" one side until the pins are seated and when you hold the mould up against a strong light you cannot see any light. This means the blocks are flush and not warped.

Now clean all the outside surfaces on the wet/dry paper moistened with alcohol, Windex, or Kerosene. The fluid acts as a lubricant and floats away the metal.

Get the sprue cutter and break the edges of the hinge hole with the 90 degree chamfer tool.

Now, using a figure eight motion, clean the bottom surface of the sprue cutter on the wet/dry paper. Note again bright areas. This will show how flat the plate is or is not.

Clean all the parts carefully with alcohol and reassemble.

Cast a few bullets to check for roundness. Measure at each side of the seam and in the middle.

If the bullets are more than 0.002" out of round you may have to recheck the alignment pins starting over.

There is a good write up on mould maintenance in the RCBS Cast Bullet Handbook.

Cheers,

Dave