Lapping a lee mold, what compound?

[Revolver]

I have a beat up 9mm 6-cav 120gr lee 90387 (http://leeprecision.com/mold-6-cav-356-120-tc.html) mold that was probably pulled out of some pharaoh's tomb or something. It's in pretty rough shape, some of the cavities have scratches in them.

I realize this is a cheap mold but I figure this is a good chance to learn how to lap a mold... or at least try. I also really enjoy fixing stuff up instead of tossing it and buying new.

I would like to use this mold for 38 special.

I get the method of putting a nut on each cavity and pouting a boolit then spinning it to lap the mold. What is unclear to me is what sort of compound to use for aluminum molds?

I have read that some people use comet cleaner?

Thoughts? Thanks!

[GRUMPA]

I use the Comet only to make the cavity look like new and to make them drop out easier. If you use valve lapping compound I've seen them in 2 different grits, 320 and 180 IIRC. The compound will open up the cavities so if you use that be careful not to remove to much.

[jmsj]

junker,
I have not tried to remove scratches from cavities before but when I have to "Leement" an aluminum mold I use boolits coated w/ JB bore paste. For iron molds I have used 320 grit lapping comppound from the auto parts store.
Good luck, jmsj

[leadman]

Just avout any cleanser like Bar Keepers Friend, Comet, etc., will work. If it is really bad 600 grit lapping compound would be good.
Make a paste of the cleanser and water, coat the bullet, insert in cavity, adjust tension on bullet with the handles as you spin the bullet. A cordless screwdriver works great.
I don't cast a nut on the bullet. I mark the bullet thru the sprue plate then drill a small hole and use a drywall screw with the cordless screwdriver to turn it.

[Maven]

"I have read that some people use Comet cleaner?"

junker, You can use Comet, but it is more abrasive than say Bon Ami, which is my preference. Toothpaste will also work and you don't have to do anything but apply it to the bullet. Btw, if you use scouring powder, try making a paste with oil, e.g., ATF instead of water, and apply it to the bullet as you normally would.

[DLCTEX]

If you just want to polish the cavities, the cleansers and toothpaste all work. If your intent is to enlarge the size of the boolit then something like fine valve grinding compound is called for. I would suggest that for the latter you embed the compound in the boolit by rolling it between two steel plates, keeping the abrasive only on the bands so that the nose and/or the gas check isn't enlarged too much.

[Ben]

Junker,

Try this :

http://castboolits.gunloads.com/showthread.php?t=47669

[StrawHat]

.... I mark the bullet thru the sprue plate then drill a small hole and use a drywall screw with the cordless screwdriver to turn it...

If you use a drywall screw, be careful the boolit does not grab and the screw bores into the mold. Actually, any long screw can do this but a dryall screw is what I have experience with. I now drill the bullet and use an Allen set screw to turn it. The blunt tip prevents it from going through the boolit and scoring the mold.

[Ben]

If you use a drywall screw, be careful the boolit does not grab and the screw bores into the mold. Actually, any long screw can do this but a dryall screw is what I have experience with. I now drill the bullet and use an Allen set screw to turn it. The blunt tip prevents it from going through the boolit and scoring the mold.

That is a very good point you've made ( please excuse the pun ) . I purposefully dull the point on the screw ( on a grinding wheel ) so that it cannot make its way any deeper into the bullet.

[BoolitSchuuter]

I've drilled a hole in the boolit base and screwed the felt wheel shank from a dremel tool into it. I used a tap handle to turn it. I wouldn't use any grit coarser than #600 on an aluminum mould. IMO anything coarser cuts too fast and you chance ruining the mould. Keep the compound out of the loob and crimp grooves. You chance making these too shallow to hold enough loob or lock in the boolit. If you find you need to do considerable lapping to remove deep scratches, I also recommend taking a couple of test casts while leementing your mould so you know where its at in the process. It will also allow you to judge if one or two cavities are starting to get out of round. Another advantage is you can bring all cavities to the same diameter by paying attention to which boolit came from which cavity. :castmine: