Ball End Mill Cutter Mold Modification

turbo_1889

Ball End Mill Cutter Mold Modification

Postby turbo_1889 » Tue Mar 24, 2009 5:13 pm

Okay first off I'd like to say - IM NOT TALKING ABOUT YOU, THE MOLD CUTTER, DOING THIS. I'm talking about me doing it myself very carefully with a drill press and jig set up after the fact.

If I were to design a 303-brit, 7.62x54R dual purpose mold with a 0.20'' flat meplate and then when I got it take a 13/64'' ball end mill cutter and chuck it into the drill press. Very carfully set the depth stop and then center her up on the cavities from above would that finish off the mold to make nice round nose "Postal" style bullets. How much risk do I run of just wrecking the mold all together trying this.

Here is a before and after picture to show what I'm talking about:

Image

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mtngun
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Re: Ball End Mill Cutter Mold Modification

Postby mtngun » Tue Mar 24, 2009 6:59 pm

You've put a lot of effort into planning this. You must really want that streamlined nose !!!!!

Drill Press ?????? I hope your drill press is sturdier than mine. But I suppose it could be done, for one cavity. Matching two cavities -- especially on a drill press -- would take both skill and luck.

Assuming you succeed in centering the cavity, and things cooperate while you are drilling the nose, the worst that would happen is the transition between the ogive and the round tip might be cosmetically flawed, rather than seamless as in your drawing. It would probably shoot fine, though.

As far as "wrecking the mold," things that could possibly go wrong would be 1) chip damage 2) mold or drill press table moves while cutting 3) new nose off center.

You can get other shapes, like 90" drill/mill bits for a pointier nose. There are specialty tool makers like micro100 that make a variety of fancy shaped end mills, i.e., tapered, flame (not cheap, though). Or, if you are a 1st rate tool grinder, perhaps you could regrind a drill bit to a pointy shape.

Interesting idea.

turbo_1889

Re: Ball End Mill Cutter Mold Modification

Postby turbo_1889 » Tue Mar 24, 2009 9:14 pm

The reason I'm trying so hard to get the nose streamlined is because these won't be cast from a lead alloy, and they won't be for low velocity loads, they will be cast from 99% pure zinc plus a little copper an alloy with about 3 times the hardness of type metal.

Now don't get all bent out of shape upon hearing that. Most casters think zinc is evil by it's pure nature. Granted when mixed with lead it does some pretty evil things to the lead pot but when used all buy itself in it's pure form with maybe a few newer pennies absorbed into the mix it's just fine. Newer year pennies are an alloy of mainly zinc with some copper, due to the copper in them they don't melt nicely at 1,000-F like the pure zinc but instead kind of slowly dissolve into the pot of pure zinc kind of like ice cubes in water. The copper does the same thing to zinc as tin does to lead -- make it a lot easier to cast with and a little harder.

Long story short 99% Pure Zinc + Newer Pennies + 1,000-F casting temp + Steel, Iron, or Brass mold makes very strong cast bullets that can handle full power, full pressure, jacketed bullet type loads. They also qualify as lead free to comply with hunting limitations for certain areas among which are an area I hunt. There is a weight difference the zinc alloy in question has about 2/3 the density of WW alloy so any bullet cast out of it is going to be about 2/3 the weight it was with WW alloy. About the same situation as solid copper bullets, they work just fine as long as you take this into consideration and load them fast and lean. For example my bullet design says it weighs 210gr. WW alloy, that's a 140gr. bullet with my zinc/trace-copper alloy. Plenty of full power loads for that bullet weight in the intended cartridges.

Casting procedures & cautions with zinc alloy. Obviously higher temp means propane burner and steel or iron pot along with extra care on the operator???s part. Separate pot and ladle should be used and don't ever use the same back and forth with lead. Molds can be swapped back and forth between the two metals just so long as you???re willing to send the first ten or so casts from the molds into the garbage can when switching. Aluminum molds should never be used with zinc alloy, at the temperature you have to get the zinc up to for it to cast easily aluminum is almost at it's melting point and aluminum like copper alloys with zinc very well. Long story short your aluminum mold will start dissolving into the castings (don't ask how I know this). ONE MORE MAJOR CAUTION: ZINC FUMES ARE LIKE WAY WORSE THAN LEAD FUMES, WHEN SOLID ZINC IS MUCH LESS TOXIC THAN LEAD. WHEN MOLTEN IN A VAPORIZED FORM ZINC IS MUCH MORE TOXIC THAN LEAD. ZINC CASTING REQUIRES DIRECT MOTORIZED EXAUST VENTALATION OVER THE MELTING POT. For my personal set up in my shop I have a chimney style stove pipe flue going up through the roof with a exhaust fan pumping the vapors from about a foot above the pot up and out. The fan always gets turned on before the pot.

Anyway, long story short that's why I want the aerodynamic nose shape so bad. Figured as long as I'm mentioning zinc based alloy casting - I'd better spill the whole story unless I wanted a whole bunch of flame posts and questions headed my way.

As for the drill press -- mine is a big cast iron giant from like the 50's that would take hell and high water, 4+ big strong men, or a forklift to move. It's table has four direction clamping capabilities and I've made myself a few simple molds for paper patching by drilling out molds cheap Lee molds with a drill bit of the right size as well as a tumble lube only, no lube grooves stepped design for 25-ACP bullets using progressively smaller drill bit heads drilling into the jaws portion of a set of bull-nose pliers. Use a razor knife to cut the spruce flat with the top of the pliers and those bullets work reasonably well. Pretty convinced I can do the drill so long as I can hit the center and get the depth stop adjustment dead on. On of those things where its a one shot only thing either it's going to work or it's not -- no second tries. Once I spin that big wheel and lower her down into the mold there isn't going to be a second try.

Just trying to get some feed-back from you before I proceed.

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Re: Ball End Mill Cutter Mold Modification

Postby mtngun » Wed Mar 25, 2009 8:32 am

Your zinc-copper alloy sounds like a fun project.

A few questions, just because I am curious......

Do zinc bullets foul the barrel ?

Do zinc bullets expand/hold together on game ?

Is it difficult to cut the sprue (I'm thinking of the large sprue hole that I normally use with WW) ?

turbo_1889

Re: Ball End Mill Cutter Mold Modification

Postby turbo_1889 » Wed Mar 25, 2009 1:49 pm

Zinc bullet barrel fouling seems to be very minimal compared to lead fouling. Zinc in and of itself has lubricating properties (google industrial zinc based high temperature lubricants) and you can actually shoot them un-lubed although this does give more fowling then if you lube them. Basically zinc fouling takes the form of a very thin plating of the inside of the barrel. It doesn't plug the rifling grooves like lead does just basically ''galvanize plates'' the inside of the barrel both the lands and the grooves. When properly lubed this is very minimal and when you switch back to jacketed or lead loads the plating effect gradually dissipates. Barrel constriction seems to be barely measurable from my experiments. I have been able to register a thousandth difference between a heavily-plated / zinc-fouled barrel and a clean bore. In other words a 0.308'' might end up about 0.307'' but that's about the extent of it. Haven't tested extended use of un-lubed bullets though personally so I can't be completely sure.

As far as impact ballistics are concerned it's basically like shooting FMJ military rounds or non-hollow point copper solids. They just punch a hole clean through. I've got a Saeco iron mold designed to cast a 30-cal 196gr. TC rifle bullets that I use to make 130gr.-ish zinc/trace-copper alloy bullets out of and load them up for the 30-06. Cleaned out a lot of coyotes with that load but you have to aim for the neck to make a good clean kill. Chest cavity shots just punch a pin-hole through them. Which I suppose if you really hated them and wanted them to suffer that would work but I'm not quite that mean spirited (yet). Now if on the other hand we are talking about the solid 20ga. slug molds you have cut for me those with the zinc/trace-copper alloy drop big slugs in excess of 60-cal. Those don't need to expand to make a chest shot work !!! Taken one deer last season with that set up so far -- more will follow this upcoming season. Nice to finally have a non-lead shotgun slug load for the river bottom area for hunting season. Was stuck using those unreliable and expensive Remington copper solids before that.

Now as far as cutting the spruce plate -- You are right indeed that it takes a little more to cut the spruce when using an alloy that's three times harder than type metal. If you time it just right and smack the spruce plate right after the alloy has just barely solidified it's possible to cut the spruce with the conventional wooden dowel mallet. Trying to do that though I get the timing off more often than not and either cut to early and smear or let it go to long and have to beat the living sh*t out of the spruce plate with the usual wooden dowel. I've gone to using a brass head ball ping hammer. As long as you're careful to only hit the steel spruce plate and not the brass mold body (if using brass mold) that works just right. As far as your spruce plate set-up; they actually stand up the best to this kind of abuse because they are made of nice thick steel plate and the spruce plate attachment bolt is much bigger and stronger compared to most commercial iron molds from Lyman, RCBS, and Saeco.

Now as far as the actual question under discussion at the beginning of the thread namely modifying a mold as listed. First I think I'm going to do a test run or two on some cheapo Lee molds before I actually order one of your molds and try it. Secondly, am I correct in that a brass mold would be less likely to chip during this procedure than an iron one?

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Re: Ball End Mill Cutter Mold Modification

Postby mtngun » Wed Mar 25, 2009 9:04 pm

Thanks for the info on shooting zinc bullets.

Regarding the sprue holes, I normally stock two sizes for a given block. When a customer specifies WW, he gets the large sprue hole, because WW sprues are effortless to cut (once the mold has warmed up) and WW fills out better with the bigger hole.

If a customer specifies a hard alloy or a BP alloy, then he gets the smaller sprue hole, which is still bigger than on some other brands of molds. The smaller sprue will be easier to cut. If you are specifying WW on the design, but intend to cast zinc, you could add a note requesting the smaller sprue holes. Even my "small " sprue holes are probably bigger than ideal for zinc.

I haven't had a problem with my iron molds chipping. It is ductile iron and behaves similar to mild steel.

How is the as-cast diameter of your zinc bullets ? Do you size them ? Are they difficult to size ? Just curious.

turbo_1889

Re: Ball End Mill Cutter Mold Modification

Postby turbo_1889 » Thu Mar 26, 2009 5:03 am

Sizing -- now that's a whole world unto itself when it comes to zinc castings. First off if I can get away with not sizing them that's what I do. If I must size them then it's a Lee type push through press mounted sizer in a strong press and it is best to heat the bullets to about 300 degrees first -- no joke, a Lee small size ladle pore pot turned way down works best for this. Zinc is very resistant to compression and not very malleable at room temperature with a very rigid crystal structure, heating them slightly up about the 300-F range makes them much more malleable -- that's a common characteristic with zinc alloys.

Lubing is always done separate from sizing if sizing is done at all. Zinc castings seem to have about the same amount of shrink factor as low tin lead alloys such as 30:1 with ''as cast'' diameters from the same mold being about the same with both metals.. I was intending to set the diameter of the mold to the diameter of the bore with the tolerances on the plus side with zinc, like jacketed bullets, you don't need to be a thou over bore size, you can be a thou under and they still shoot pretty straight. In addition zinc is slightly pickier than lead about fill out when it comes to narrow bands and lube grooves -- you'll notice how I'm keeping the bands and grooves nice and wide.

So anyway, at this point I'm basically considering working up into molds specifically designed for zinc casting. As far as the spruce plate holes; just like WW alloy zinc alloy really likes a big spruce plate hole. Think I'll be sticking with the larger WW spruce plates if they are harder to cut. First thing I had to do with my Saeco mold by the way - expand the spruce plate hole (used a counter sink cutter bit to get approx. the right angle) along with drilling out the gas check shank on the mold to make a normal base. Similar operation to what I'm considering except for expanding a hole with a drill press is pretty much a self centering operation. That thought does give me and idea though. I could use that same counter sink cutter with it's steep angle to center the drill press on the molds bore. First with the mold halves firmly clamped together and the mold sitting on the press table lower the counter sink cutter (motor off) down onto the mold bore hole, then clamp the mold in place, and finally raise the drill press head swap out the counter sink cutter for the ball end mill cutter. Theoretically, that would make sure I was centered dead on and not just be trying to eye-ball it. Got to order a batch of cheapo Lee molds and the ball end cutter and start doing some testing . . . . :?

It might be some time before I actually put in the order for the first mold specifically designed for my zinc casting. Need to work all the bugs out of this round nose idea first. I think you see where I'm going though. Nose profile built for high speed full power load velocity, mold that drops bullets at bore size (in this case both my 303-brit and 7.62x54R are same so two guns with one mold) or just slightly under or over by a thous so no sizing, large size holes in the spruce plate, and nice wide body bands and lube grooves for proper fill out especially an extra thick base band with no gas check shank.

turbo_1889

Re: Ball End Mill Cutter Mold Modification

Postby turbo_1889 » Sun May 31, 2009 1:25 pm

Well, I finally got a cheapo Lee mold test run done to see if I could get it precise enough with my drill press set up for it to work. Took a Lee TL314-90-SWC double cavity mold and tried to round nose it. It's basically a SWC or TC, which ever one you want to call it intended for 32-caliber revolvers. I have got it to work fairly well for loading 32-ACP but do get a few jams on feeding with one of my pistols due to the flat nose. Figured it would be a good test run and would improve the mold for what I'm using it for. I found a drill bit of the proper size to just match the diameter of the flat tip and then chucked it into the drill press and let it spin while I used a fine grit diamond little knife sharpening file stick I have to shape the end of the drill bit until it had a very nice smooth curve. Sort of a pore man's grinding lathe operation. Once that was done I used a depth setting locking collar on the bit and adjusted it by eye-ball up against the mold half until I looked just right and then I tightened the living daylights out of the set screw.

Once I had my cutting tool made I very carefully centered the cavities up under the drill press using the counter sink bit with the drill press turned off as I described earlier and then swapped out the bit for my home-made depth set cutter and then cut each cavity in turn. After that was done I used a cu-tip chucked into a cordless drill with just a drop of fine grade valve lapping compound on the end to lightly polish the bottom of the cavities. Then I cleaned up the mold and cast some bullets with it to check how it had gone. One cavity turned out perfect and the other the ball nose is just a little bit off center, not a whole lot but enough that you can see the difference with the naked eye. I'm not sure yet if it will affect accuracy enough for the short range shooting of the 32-ACP caliber enough to worry about but I wouldn't want that inconsistency on a rifle mold cavity that's for sure. My method of centering up the mold under the drill press was the exact same for both cavities so I'm not sure what went wrong. However, the test has shown me that my equipment and method is not precise enough for me to risk attempting this myself on a $100+ custom rifle mold intended for 100+ yard accuracy. My next step is to see if Eric who is the man behind Hollow Point Bullet Mold Service (http://hollowpointmold.com/) would be willing to do the modification after initial cutting or not. He has CNC equipment that is far more precise then my drill press modification attempts.

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Re: Ball End Mill Cutter Mold Modification

Postby mtngun » Sun May 31, 2009 3:59 pm

Thanks for the update. You did well considering you are limited to a drill press.

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Re: Ball End Mill Cutter Mold Modification

Postby mocons » Sat Jul 09, 2011 11:28 pm

Hi There ,
I have not yet read this entire topic, but I have a bit of experience with zinc and copper alloys, and the company that I work for is about the second largest user of a proprietory GM zinc-copper alloy that we use in both hot and cold chamber high pressure die casting presses. (it was intended for use in hot chamber ops. but we have established that the alloy works best in the cold chamber application.) I have done some work along those lines, and Yes; the alloys are very "self lubricating"; in fact we actually use the metal to make some rather massive self bearings that have proven to be very effictive. The Alloy combination is about 5% copper, and the final result is a very dense casting with a much higher quality than "normal" surface finish. I believe that the alloy has a great possibility as a bullet material ( look mom..lead-free!) The alloy has a density of about 6.8 as opposed to lead's 11 odd, so there is a downside. eh? Also.. The melt must be stirred constantly, it will disolve a cast iron casting pot over time ( less time than I care to admit) When used in a hot chamber casting process, we found that the alloy destroyed high carbon rings on a plunger in about 3-5 hours of operation.
mocons


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