View Full Version : Oozing Lead During Lapping

07-23-2011, 02:38 PM
I decided to try and lap my 358429 mold that was supposed to be fixed by Lyman. I used 320 grit Clover and noticed some lead oozing out between the blocks like part of the bands were coming off. I've only tried this once before and don't think that happened last time. Cause for concern or just a matter of the way it is doing this? I was attempting to not only smooth things out a little for easier drop from the mold and also to increase the band size by at least .001".

07-23-2011, 02:56 PM
Not lead. Just lapping compound.

07-23-2011, 04:16 PM
Nope, it was lead. Some compound came out but the other was thin lead shavings.

07-23-2011, 04:20 PM
It's a pain to get the lap in the blocks and started good without shaving some off, especially if the POS is casting out-of-round to begin with. Keep in mind you want the blocks fully closed so they get a fighting chance at being round when you're done, so I'd say just clean out the shavings, close the blocks around the lap again and keep going. The compound will crush down to extremely fine stuff very quickly and ooze out the vent lines.

Edit: one more thing, check to see if the cavities are cut so that it looks like the blocks shifted, IIRC the left block will be forward of the right block (typical recent production Lyman out-of-round issues) even though the outside of the blocks will mate perfectly flush. I think their boring vise is totally worn out and allows the blocks to slide away from each other under the torque load of the cherry cutter, which has a right-hand rotation. It's like two-lane traffic in England, the left block goes forward and the right one back, and when they are mated again and the alignment pins installed, the cavity halves overlap, as much as five thousandths in some of the examples I have laying around. If this is the case with your mould, the sharp edge to the cavites might be what's shaving lead. I've fixed two of my moulds by filing off one side of the alignment pins and peening the holes on the other to shift the blocks until the edges of the cavities line up again. Then I had to lap them to get them round again, and lap them some more to get them anywhere near the correct size.


07-23-2011, 06:41 PM
The driving band measured .356" and the other two varied between .357 and .358"-depending on where you measured and how far you went around the boolit. This may be an Erik job if it doesn't cast at least .359" for me. I had the mold in the handles squeezing pretty tight during all the lapping.

The blocks didn't appear to have shifted. The shaving seemed to have come from the bottom band...the larger of the three. I'll cast about 50 and measure to see if I made any progress or not and how they may now fall from the mold. Until Lyman gets it together(if ever) this is my last Lyman mold.

07-23-2011, 07:41 PM
do you think it would make a difference turning the lap the other direction?

07-28-2011, 02:14 PM
I had a buddy turn a allen headed bolt down to .360 diameter and in thickness to fit the bands in my 358429 mold. Then using 600 grit lapping compound applied to the bolt I turned it by hand in the bands with the mold closed. About 25 turns and then cleaned the mold. casts now with all bands sized by .359 sizer unlike before where only one side was touched by the sizer.