Making molds a little larger?

[rondog]

Forgive me, but there's several truckloads of info on this forum, and I don't know where to find this - but I remember reading here about methods to modify aluminum Lee molds to make them drop bullets a little bigger, maybe as much as .002 bigger? It was about making the mold cavities physically larger, not just Beagling them.

A little help finding this, please? Pretty please?

[Bulliwig]

Sometimes it is enough to:
-cast bullets and let them stick in the mold
-drill a hole in the center of the bullet and screw in a drywall screw
-coat the bullets with a LITTLE (important!) fine grit lapping compound
-turn the bullets with a drill on the screw

This will take a lot of time (and a lot of bullets) to open the cavities up, but it is easy ans unlikely to detroy yout mold. I don't know how fast ist will cut aluminum molds, I've done it witz my Lyman 421429 and I tell you, it took long....

[country gent]

Do a search for Lapping moulds. Lapping a mould larger was the original process years ago. Basically you cast bullets with the mould to get a few good bullets, ID these to the cavities if a multi cavity mould, Ideally you want 3-4 from each cavity. I drill a hole in the base for a stem of 1/8" key stock as deep as possible with out breaking thru. I then glue a stem into a couple bullets to start with. This is your lap for polishing reworking the cavity. I woork by hand with a t tap handle on the stem. Lightly coat the lap with fine lapping compound, this is starting grit is determined by how much needs to be removed. I usually start around 280 grit or 320 grit. Gently insert the lap into cavity and close blocks around it. work in a back and forth rotation ( aout 1/4 - 3/8 turn) 3-4 times and rotate 1/4 turn repeating this thru 2-3 rotations. Clean cavity and look for the clean up pattern. If cleaned up gop to a finer grit and repeat. This time clean mould and cast a few bullets to measure and see where your at size wise. On multiple cavity moulds the rotation is done thru each cavity starting off by one cavity each time. Lapp cavity 1,2, *** then cavity 2,***,1 . then *** 1,2. thru each cavity. This keeps the lapps even and cavities close to same size. I ussually work to 600 or 800 grit then lightly finish with flitz or simichrome polish. Remeber that .001 removed on a side is .002 on the bullets dia. It doesnt take alot of compound and lubricating it with a light oil or water depending on compound helps alot here. The compound will break down acting as a finer grit as you go also. Lapping a mould will allow you to obtain the correct size you want iot does take patience and time work slow and carefully

[Ballistics in Scotland]

If you do it on a drill press, any sideways pressure will make the mould lopsided. If you do it freehand or it shifts in whatever is clamping it, you are liable to get it angularly lopsided. But if you don't apply sideways pressure, it will enlarge the ogive and the rear of the lube grooves more than the diameter.

The best way is to do it is on a lathe with the mould rotating, using a micrometer boring head. starting with the lap held straight in line with the cavity axis, and then move it slightly, just as you would with a boring tool. Sideways pressure is harmless then.

The smallest boring head, available on eBay, isn't unduly expensive as lathe tooling goes, and it isn't the sort of thing the mould manipulator will use only once.

http://mecha-tech.la.coocan.jp/boring_head/boring_head-e.htm

When I did it I had the advantage that it was an iron mould, which laps well. I filed the top of the lap flat to admit more paste, which in my case was a syringe of diamond paste from China on eBay, surprisingly cheap for diamonds. But you could do just the same with any abrasive and oil.

[toallmy]

Take a look in mold maintenance and design , a lot of useful information on lapping a mold , Lee aluminum is pretty easy to polish out a little . You just have to take your time to get the cavity all the same . You can do it by hand with a 1/4 in nut driver so you go slower and don't overdo it .

[GhostHawk]

I did my .312 185 gr gc by hand w ith a nut driver.

Moved the sprue cutter out of the way and poured the hot lead through the nut placed over the hole.
Cooled, trimmed, and kept cleaning the mold, paint a thin layer of polish in the area I wanted larger and only in that area. Took less than half hour to go from dropping .310-.311 to .3145 or .315 which I would size to .314 and crimp on gas check.

[longbow]

I was going to direct you to Cast Pics where there are a couple of articles, at least, on lapping moulds but I can't find it now!

It is not too hard to remove a thou or two especially from an aluminum mould but you do want to be careful and take it slow with lots of cleaning between runs or you tend to get an oval cavity.

I'll see if I can find out what happened to Cast Pics as it had loads of good info on it: old loading manuals, Lyman and other bullet mould info, articles, books, load data... in general a wealth of information.

I likely have a PDF of the lapping article so I will try to find it.

Lapping is fairly easy if you take it easy and read/learn before doing. Once metal is removed it can't be put back! I have successfully lapped several moulds to enlarge them by 0.001" to 0.003" and in one case to even out offset cavities and make them all the same size... and larger than they were. A couple thou is pretty easy going.

If I find Cast Pics or the article I will let you know.

There are a couple of good posts on lapping as well so try the search and you may get what you need.

Longbow

[longbow]

Hah! Found a back door:

http://castpics.net/subsite2/MoldMods/MoldLapping1.pdf
http://castpics.net/subsite2/MoldMods/Fixing%20Lee%20Molds.pdf
http://castpics.net/subsite2/MoldMods/How%20to%20Hone%20Out%20a%20Mould.pdf

Not sure where the link is on the site anymore but a search found a way in.

I recommend using the cast through a nut method in the first article and a relatively fine grade of valve lapping compound. It is hard to remove too much metal too quickly turning by hand. it is easy to remove too much metal when using an electric drill or drill press.

Longbow

[Ballistics in Scotland]

If you must do it freehand, an electric screwdriver is probably best. It is faster than doing it by hand, and yet too slow to build up a cyclic wobble. All electric drills have the armature unbalanced to some extent, or they wouldn't vibrate at all.

[Traffer]

Hah! Found a back door:

http://castpics.net/subsite2/MoldMods/MoldLapping1.pdf
http://castpics.net/subsite2/MoldMods/Fixing%20Lee%20Molds.pdf
http://castpics.net/subsite2/MoldMods/How%20to%20Hone%20Out%20a%20Mould.pdf

Not sure where the link is on the site anymore but a search found a way in.

I recommend using the cast through a nut method in the first article and a relatively fine grade of valve lapping compound. It is hard to remove too much metal too quickly turning by hand. it is easy to remove too much metal when using an electric drill or drill press.

Longbow
Wow, I just got an education. I have only been casting bullets now for about 8 months and have only done 6 to 8 casting sessions. Mold design was a mystery to me. Didn't know that the marks on the face were vent cuts. Didn't know that you should only tap the center bolt on the mold. And all the rest. My Lee molds were purchased on eBay for less than $25 apiece. To say I have been brutal on them is an understatement. At least I have been careful on the cavities themselves. But the rest ... embarrassing. The article on fixing up Lee molds was particularly enlightening. Don't know if it would have registered in my mind before beginning to cst but now I understand it and can respect it. Fortunately only one of my two molds has been brutalized. And that one not beyond use. I would recommend that everyone who casts read the article on fixing Lee molds.

[GhostHawk]

Like you I totally trashed a couple of molds before I got eduamacated.

The good news is once that light bulb goes off you are cured for life.
Mostly a matter of a little care and consideration.

When you think about it a couple of 20$ molds is really pretty cheap considering the cost of higher education. Even the school of hard knocks isn't free.

[sundog]

I recently purchased new 2 Lee tumble lube 6-cav moulds, 158SWC and 430SWC, knowing that they would be marginal at best for .359 and .432 - and they were. Both were intended for use with powder coat, and to that end they are perfect. The newer Lee moulds seem to be a little better tolerance than years past, and these two moulds are no exception - very nice and fairly consistent cavity to cavity, and round. All I did to them when they arrived was my standard Lee-ment routine and cleaning.

I opened up Lee push thru dies to .359 and .432 using 600 grit and crocus cloth to polish ala roll on a stick method.

The boolits were cast with COWW, AC'd, pc'd with HF red via shake and bake and then run thru the respective size dies. Very usable boolits!

The .359's were loaded in Starline .357 mag cases, Win SP primer, and 10.0/AA#7. Accuracy is acceptable in several hand guns. They also feed and function in a Rossi 92 with acceptable accuracy.

The .432's were loaded in RP 44 Spl brass, Fed LP primer, and 6.0/Unique. They were shot in a 44 Spl Blackhawk with acceptable accuracy.

I started pc'ing handgun boolits only recently, but it dawned on me (hit this country boy like a ton of lead actually) early on that bulking up a boolit with pc is a whole lot easier that screwing around with the mould - especially if you are already getting decent boolits albeit a little skosh.

That's my story.