Easy adjustable PP mold making

[Frank Savage]

Posted this on other forum also, but much more interest in stubby SWC´s and wheelweight there and not much appreciation for sleek, elegant PP slugs.
The object was to have easy and convenient way how to change bullet dia, lenght and nose shape without having to make whole mold blocks for every each attempt and all its belongings, like sprueplate, its alignement etc. Also, as not having a mill, it´s pretty hard to make usual square blocks and fit them into handles, so "lathe only" was the only availible solution. Not finished yet to real final, as you´ll see later that some tiny and a bit time consuming parts and work still remains, but I´m close.
Thanks to those members here who mentioned Ideal molds on other forums and pointed me in right direction to loose my doubts about possibility of having a sliding elemnt in the mold without problems.

You need just small lathe with 3-jaw, set of collet holders will make you very hapy and 4-jaw will help you. Add a drill, some taps and you´re done.
Disclaimer and apology regarding bullets in photos-don´t judge the longest nose bullet, I hogged eight of them from almost cold mold for lenght checking purposes. The good ones went down the barrel before.

Here´s part of my setup, for current 8x60R Kropatschek project (or 32-72-247 BN cartridge):


Mold clampholder with sprueplate, mold body, some nosepunches, bullets and bullets set into brass. It´s the easy Ideal adjustable basepour style, where the basic hole gives bullet dia, nosepunch cavity the nose shape and lenght and overall position of the punch in mold body gives the total bullet lenght. Materials used are el cheapo the most common easy machining steel-once you know what you want, use brass or some better steel. But no point having put the extra time and tooling setup into mold you may use only to prove wrong idea with 30 slugs cast.

The mold body is just a simple cylindrical hole into 25 mm or 1" cold roled bar (machinists and diemakers, don´t laugh here about the "simple cylindrical hole" ). Drilled and reamed, then honed with emery cloth to proper dia and surface. If you make a 1-1,5" cut into the end of cold roled steel about 1/25"-1/16" smaller than the hole you have and use a bit wider piece of emery cloth than the slot lenght, you can hone it up as much as 0,015 without marring the cylindricality except little on one end. Well, it takes a bit of feel and practice, but can be done. Then you get rid of about 1/6-1/5" on the drill entrance side, since from honing it will be coned-so take it into account when cutting the basic material to lenght. I use 55-60 mm (2,1-2,3") for anything up to 1,4" in lenght and works OK.
Making a set of calibers around your desired dia to determine wherether are you in or still out of the realy cylindrical part helps a lot, albeit it takes a bit of time. But even the cold rolled easy machining stock is sufficient here, since you´ll probably end up using a tad smaller caliber and narrow strip of your patching paper sticked into mold cavity to determine the dia as well as finding possible tight spots to have them honed out-while not having a chance to jam the caliber inside. The paper will let it out every time.
After cutting to the cylindrical part and facing, cut most of the face surface off to create a simple dish about 1/32" deep with rim on outer as well inner perimeter, about 1/16" wide. Then cut off the outer rim by about 0,003"-0,004" below the rim of the mold cavity. Why-later. The dish can be distinguished well in the first photo.
If you don´t have a reamer of proper size, you can go on with quite easy to make drill rod for calibers .40 and up. 11/32" or a bit bigger cold rolled stock even of 1018 steel will hold up to about 2,5" deep hole, but anything smaller will flutter, destroy the knife set into the rod and overall make a whole lotta mess. Tried it on thisone-and was not pleased at least. Will show the setup later, now don´t have the photos on hand. You must make the knife sharp, well angled and of course use little feed rate as well as small chip thickness. If you can make the drillrod from properly heat treted tool steel, you´re happy campers even at 270-300 cal., but I don´t have the possibility.
The end is then covered with cap about 1/8-1/6" thick, fitted by three 1/8" or so bolts about 1/2" long:


Attach the roughed out cap with precisely drilled holes first, then set the mold body into chuck and cut from outside to desired dia. This is the most time demanding part, since you need to drill and tap (M3 or M4 or 1/8" or 1/6" threads) the mold body for all three bolts, make a paper template by pressing the paper with your dirty thumb against the bottom face to get the hole pattern impressed and drawed onto it (do you remember school and "frottage" in arts class?). A white self-adhesive sticker works well here. Place it on flat bar or steel sheet you´re going to use for cap, drill and countersink for bolt heads those three holes, rough out the cap and fit it. When countersinking, remember that the side with the sticker is the one which will end up at the mold body, so countersink from the side without the sticker to obtain the most precise hole placement. Then (in lathe chuck) drill 1/5" or 1/4" hole for nosepunch pushrod and make sure it´s dead center, will be helpful to place a live center into it for turning the cap into mold body contour.
My final goal is to have clamp style bottom cap(s) as just make the proper dia hole and punch, but this requires to set onto 1-3 lower body diameters, which I´m still not sure about regarding heat accomodation and release, as well as possible unevenities and warpages.

Now the nose punches, where collet holders and their inherent preciosity of repeated grip, as well as surface protecting properties will help you a lot. The sequence was thought out as to make as low number clamping changes, as well as to maximaly protect surfaces of finished measurements :
Take a cold rolled bar at least 1/12" bigger than desired final dia to get rid of the tougher, roll-compressed "skin" these rods always have. Cut a small part, about 1/5" long about 0,002" bigger than desired final dia of the punch-you know this dia from using your calibers during honing the cavity. Then drill a pilot hole to desired depth, with about 1/25-1/16" adition:


Set a profile knife into your toolpost and cut the nos shape. Will have to insert the images later, made them extra blurry and worthless. But will have to make a new lenght of nose today or in few days, so it will be here.
The object is, that the outer surface will rest steady while the knife will cut from inside, leaving proper outer dia and razor sharp edge-meaning almost seamles transition on the bullet. But making a proper hole, then cutting around it from the outside where there´s almost no wall thickness will result in pressing the material into the cavity, marring the nos shape as well as outer dia and may result in positive locking edge which will lock the bullet in the mold. I hope you can understand here, if not, then just take into account that it´s much more easier to make and measure an outer surface first and cut the hole to intersect it at desired point-since you can see it all around, than opposite. Also, you can pull the material into more lenght with almost no effort-but hardly you´ll press it into more compact form without considerable force.
You want the hole a tad deeper than desired nose lenght, because to achieve the properly sharp end, you´ll make the knife cut out through the initial dia surface, so it will end up a bit shorter. As well, you´ll deepen it a hair by feeding the knife into the end of the pilot hole-but easy, due to very low speed close to axis it will have audible tendency to flutter, so not harm the inner surface.
Now use the at first made proper dia as a reference point and make the dia in whole lenght you need. You can see the profile knife on the right. With one knife, you´re not stuck to just one profile, by different angling of its axis as well as X-Y toolpost movement you can do quite a magic. All three bullet shapes in the photos here were made with one knife, albeit I´m not even a machinist, not a lathe magician. But of course, the closer the shape, the easier.




You may fing helpful to touch the inner surface extremely lightly when the outer is done to make the sharp lip even in lenght:


Then touch it with wet kind of 400, 600 and 800-1000 grit cloth or paste inside for polish. Use piece of wood or so and tapping fluid. Determine the overall lenght of the punch-to make max. lenght of your wanted bullet, or a tad more-and make a shallow cut in the middle between end of the nose cavity and short ring on the bottom end to leave bearing surfaces only on the ends of the punch. It serevs to reduce friction, as well as to make room for occasional mess which may get into the mold, preventing the nosepunch from stucking in on every impossible occasion. Also, when you get somehow uneven heat distribution while preheating the mold, the cold roled stock warps a bit and this dia reduction on part of the nosepunch shank reduces greatly possibility of stucking due to this.


Cut off the punch for lenght, set it into collet by base out (attention not to damage the lip of the cavity!), face it, bevel the edge, drill and tap a hole for proper pushrod-the thin bar visible on the second photo or here and thread the pushrod in such a lenght that with nut all way onto, the lip of the nosepunch is still in the cavity, as seen on very shallow SWC nosepunch here:

Then take again your trusty emery cloth set, some flat bar and use it to bring the outer surface those 0,001-0,002" down to proper dia, check the fit often. You can take off a bit more material on the bottom ring and from lower portion of the upper bearing part along the cavity, but you can leave 0,0003-0,0006" more than exact on the lip-with shallow aproach angle of the cavity towards the nosepunch surface it will spring this little even in 1018 kind of steel and will provide a good contact even when the body will be a bit hotter than the punch.


You can see a cylinder below the mold body-serves as a weight to pull down the nosepunch, as well as a handle and part to tap onto when the bullet does not come out by its own weight. Simple piece of round bar drilled and tapped all the way through, nothing special.

Easiest way how to set a lenght for initial experiments is to wind a clean, unlaquered cooper wire onto the pushrod, as seen here, along with nosepunch, bullet fit and ejection:



Close up of the punches and bullets. The upper two have a "delaminator ring" or "cutting edge ring" for great ease of mfg of the punch, as well as a place to give the PP a bit of positive lock for dirty bore shooting tests. With softer alloys, so bump-up is well present and no problems with uncut ring of paper there thus patch stucked on bullet:



NEVER use a steel wire, it may got the surface loose upon heating, resulting in grit in cavity and ugly stuck nosepunch, maybe even destroyed mold. Wind it tight, or you´ll find great difference in bullet weight even with the best casting technique due to springing of the spacer. Different mold temp will also move you more than you´re used to, so use it in this manner only for lenght testing purposes and make proper one-piece, preferably brass spacer for real work.

The clamp holder is somehow self-explaining, just one photo from making the clamp head:


Here the independent 4-jaw will be helpful. Use at least 7/16 or 1/2" flat bar, but be damn sure that 3/8" is too thin. Two hints-make the dia just for your bar stock and, without removing it from the chuck, face the outer flat surface on which the sprueplate will be placed. Don´t rely on the basic bar and "it´s laying dead flat on the dead perpendicular face of the chuck". Did that, couldn´t make the bases square and found out that when drilling the basic hole, one edge moved a little bit upon cutting the hole, which then was not square to the surface. A mess to find this out on finished clamphead.
The handle is simply a lenght of about 1/4" thread rod threaded into the clamphead, with a piece of tube slid over it, fixed by those two handle heads. The handle wood is young black locust stem, finished with tung oil. The handle is cold browned the usual way. The clamphead itself and sprueplate were left in the white, getting usual greyish blue colour from use.


Make the sprueplate a bit freefloating-let it some up and down play. You´ll adjust the mold into the clamp in such a manner that only the inner lip around the cavity will touch it, or better place a piece of your thinnest patching paper onto it and the set the mold block as to have full contact, but still not lifting the sprueplate up. This way you´ll get a ventilation. It is very easy with the sprueplate set rigid achieve such a hermetical fit, that the air can not leave the mold and for God or Hells sake you can´t pour a bullet. Also you´ll se here why to make the outer lip a tad shorter-if you don´t, you can´t see the moment of proper contact and you may find out that it´s obstructing the way of the sprueplate by some 0,001´s, making bases unsquare and with lip of lead on one side. Tedious to clear them at least.
May sound weird, but the most accurate setting is done in front of light, seeking "see it-don´t see it" or after a little practice just by feeling of just lifting-now not lifting the floating sprueplate. Get used to to touch the sprueplate bar a bit by laddle to make sure it´s not lifted. May sound inconvenient, but you´ll get used to it very quickly.


This way you can for little effort and costs find out the proper dia for your bore and paper combo, as well as something for different oddbals you may encounter. Also, you can try how much accurate is the Greenhill formula for your rifle or whatever "just on the edge" or beyond it you want try. Also, you can make yourself a somehow conical driving portion of the bullet very easily.


This mold casts bullets rounder than 0,01 mm or better than 0,0002" for me, while I managed to keep the tolerance between the nosepunches and mold body at about 0,0001-0,0002". Way easier when you have a metric micrometer in milimeters, since you have 2,5 times it´s basic division (a 0,01 mm) in 0,001" and it´s way cheaper than 0,0001" divided micrometer. But for practical purpose 0,0004-0,0006 " is better clearance, since the fit and seal is still perfect and the temp differences does not so much for nosepunch sliding ease-I then moved that way on most of the bearing surfaces lenght. Hard to measure it, but you´ll definitely feel it when try the movement of the nosepunch. Free all the way, but especialy at the bottom of the stroke (in position for desired bullet lenght) just not dragging.
Some may not believe in bullet base squareness with this design and "free floating sprueplate, but I tried to make a pure tin bullet, set it into collets and was unable to measure anything wrong with 0,01 mm dial indicator set in holder firmly clamped in the toolpost. Not hard, if you make the hole and face in one clamping into the 3-jaw.
The outer diameter reduction on the lower mold body is for the purpose of lesser metal keeping heat around the nosepunch, since I found out that with 1" bar and .30 cal hole, this part can get pretty hot and the punch starts to drag. As well as too much metal makes great need for heat to get onto initial temp, so a bit of other inconvenience, as several (like 10-12) preheating pours can not bring it to desired temperature and "shi*ty" noses results. The 1" bar is proven for me for 45 cal molds, but will work for 50 too I bet. But those without the dia reduction, probably 40 cal. being the last to do that and leave the bigger ones as pure cylinder.

[Don McDowell]

Thanks Frank, great post.

[Lumpy Grits]

Outstanding Frank
Gary

[Frank Savage]

Update:
Use steel nosepunches for test puroses and small batches only, esp. if using 1018 or some easy machining steel. The punches go through some temp changes during casting, way much more than the body, which has some effect on the nosepunch surface. When the mold is on full heat for about an hour, it tends to occur a crust of deep blued metal, which upon cooling cracs and forms burrs. Stuck nosepunch, deeply scratched body of the die is result. Founf this the hardest way just now, when wanted to make first bigger batch. If made from heat resistant or tool steel, or cast steel bar, it may not be an issue. But this just ruined my day.
Going to make new body (steel, fast) and latest nosepunch from brass. Will give report how it come out.

[Frank Savage]

The tolerances I used are too close. It does not matter on the nosepunch lip, as it can spring. But along the nosepunch shank where the wall is thicker, it has to be about 0,001-0,0012" to be realy safe. If I had this "gap" I may have not ruined the mold-probably may had to clean up the nosepunch surface only. Also, it seems that the dia reduction on the mold body has some relation to total bullet lenght. I´ll have to photo and draw sth to explain this clearly.

Made new mold body-took 2 hours due to biting into tongue to make it just the same dia as the previous while freehand honing and polishing it (well, the machine is quite too small and almost asks for steady rest for the basic 2 3/8" long piece of 1" bar, so I must go gently and slowly). But worth the result, bullet from previous body slides in with very similar speed by its own weight, albeit I was some 0,0001-" off. So had to take this 0,0001" or less from nosepunches I already had. Made them better clearances too.
The brass nosepunch turned out well, bullet just 5 grs shy of the previous steel one at drop-and-go test with no adjustment due to slightly sleeker nose profile. But I hadn´t the paper with X-Y movements I made on the original, as well as I´m not used to turn brass and look into shades on it (read it as "advanced eyeball measurement procedures")-too shiny. Made the tolerances more generous also, except the lip-and man, seems it works wonders. Way better and smoother feel on movement when heating up and finaly hot.
Also I probably stumbled upon something about the "dished" upper surface and semi-floating sprueplate, as I had one of the most enjoyable sessions ever with those about 30 I just finished for test. Perfect and easy filling, no vent problems, perfect square bases, no sprueplate overflows... Will verify the thought and post.