Cut My Own Mould

[nhrifle]

Well fellers, I gave it a shot and cut a mould. NOE hasn't made another run of their 50 BMG mould and I want to cast for it to make my shooting a bit more affordable and just to see if I could make something shootable. My first effort is a bit of a disappointment but it did serve as a good learning experience. I know the mistakes I made and what I need to do differently on my next. I will make this work!

I made the blocks from 6000 series aluminum with 3 alignment pins. The sprue plate was taken from another mould to expedite things, so it is a bit undersize for the blocks, but did serve the purpose quite well. The cutter I made is a 4 flute design, with a .501 bore riding section, .512 driving bands, and three deep lube grooves, and a target weight of 800 grains. I slotted the blocks to fit Lee handles.

All in all, I don't think it was too bad a result for my first grease groove mould. It took me about 4 days off and on to finish, most of the machining being pretty basic stuff. The mould halves don't line up with each other perfectly and fill out wasn't great. The driving band is too thin, and both the bore ride section and the driving bands are undersize by a few thou, .498" and .507"/.509" respectively. I have no doubt I could send these down the bore safely, but I can only imagine the leading I would get! On a happier note, I couldn't be happier with the weight -- 875 grains! These things are huge!

87775
This is my cutter before I milled the flutes. Made from O1 drill rod.

87776
Not a great picture, but a view of the cavity.

87777
Here's the mould assembled on handles.

87778
Finally the mould with a few of the boolits I cast.

This project didn't work out, but I am not giving up yet. I had fun and learned a few things. If nothing else, I made a pretty cool ingot mould! I'm still hoping NOE will be making another run of their BMG moulds though... Swede? Help me out?

[Love Life]

Is the release agent causing the smaller diameter?

[nhrifle]

If it is, only just a little. I tried casting without the release agent, but fill out was horrible. Those were undersize as well. Next mould will have vent lines and hopefully will fill better. I think the reason they are undersize is I didn't figure in shrinkage when I made my cutter. I am trying to find a formula that will get me in the ball park so I can figure how much larger than target diameter the cavity needs to be cut. Perhaps someone on here can chime in and figure how much over cast size I need to go.

[CastingFool]

Go online and do a search on shrink rate of lead. I did and found this.
http://www.muzzleloadingforum.com/fusionbb/showtopic.php?tid/234730/

[nhrifle]

I gotta work on my searchfu, never came across that! Thanks for posting CastingFool!

[Doc Highwall]

Check out this site.

http://www.lasc.us/CastBulletNotes.htm

[nhrifle]

More good stuff, thanks! I will have to go over those numbers more carefully, but it looks like I will need to cut the cavity about .0045" oversize to get what I am looking for.

[theperfessor]

Good try, I bet your second try is successful.

If I might offer a suggestion -

Do you have another mold made from the same material? Measure the base band diameter. Then cast some bullets in the mold and measure the same feature on the bullet. Shrinkage is proportional - if it takes 0.003" difference for a .30 caliber bullet to come out the right size, then it will take 0.004" for a .40 caliber mold and 0.005" for a .50 caliber.

(I'm guessing at the numbers, I picked them as an easy way to illustrate my point.)

Remember, it's not just how much the lead alloy shrinks, its also how much the mold cavity expands as the mold heats up to casting temp.

[nhrifle]

Hopefully on my next mould the halves will line up better. That was my fault anyway, I rushed into cutting the cavity without having the blocks squared up properly and using only two alignment pins rather than three. They shifted when I cut them. Oh well, live and learn. Before I go crazy making new parts I'm going to try facing .010" off the inner faces of both blocks and try to recut the cavity, again just to see what happens. Maybe that will work. If not, I am going to proceed with a revised procedure for cutting the new mould. I am going to make three cutters, one for an initial plunge cut into the clamped blocks to establish OAL, a second to open up the bore ride section to .505", and a third to cut the driving bands to .516". Somehow I will make this work.

[TomAM]

The Perfessor is right; Alloy shrinkage is only part of the equation. Aluminum block expansion is substantial at casting temp. Still, you need your cherry to be about .003" larger than desired bullet diameter. You already have the exact answer, though, because you now know how much smaller your boolit is than your cherry.

[Doc Highwall]

Do you have a rotary table and a Bridgport? You could rotate the table truing up the off center part and open the cavity at the same time but not much room for error.

[nhrifle]

Doc, don't I wish. I am working on the Harbor Freight clone of the Seig X2 mini mill and no, no rotary table either. GRRRRRRRRR. So much I could do if I had the tooling. My mill is good and cuts way better than it should, but it does have serious limitations on axis travel. I think by milling the faces of the blocks I can reduce the size of the cavity, leaving the majority of the cavity intact to guide the cutter. May or may not work and I will definitely be making a second one with improved dimensions.

I can't express properly my appreciation of everyone who has posted advice on how to proceed. Keep 'em coming! There's more than one way to skin this cat!

[zuke]

I'm impressed, for a first of it look's nice!

[rattletrap1970]

I didn't notice vent lines. Unless I'm mistaken for proper fill out you're gonna need ample venting.

[dkmulford]

The cutter I made is a 4 flute design, with a .501 bore riding section, .512 driving bands, and three deep lube grooves, and a target weight of 800 grains. I slotted the blocks to fit Lee handles.


I'd be interested in seeing a picture of your cutter.

[Plastikosmd]

Could u start a thead on bmg and bp? Would love to read it

[220swiftfn]

I'll toss in a suggestion of a short section (like 1/8-1/4") of pipe welded to the top of your sprueplate so you don't get voids in the base.....

Dan

[nhrifle]

Here are a couple views of the cutter I used, basically a 4 flute reamer design
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87942

Plastikosmd, I assume you are referring to stoking the BMG case with black powder? That's something I have thought about often, and when I get enough to feed my muzzle loaders with some to play with I will probably try it. I think it would be a hoot -- the smoke and fire, almost a mini field gun effect. If anyone has tried it feel free to share your experiences.

[deltaenterprizes]

Did you do any relief to the cutting edges to sharpen it or did you use it with just the flutes cut?

[akraven]

Excellent job especially for a first attempt. I hope to do as well as you did.

[leadman]

I have often thought about cutting my own molds. Now that I am using the Hi-Tek coating there is no need for lube grooves so this might make it a little easier. I only have an old Craftsman hobby lathe so it probably won't happen soon.

When you get you mold working right if you want some of your boolits coated with Hi-Tek let me know. Would be interesting to see them shot thru the 50 bmg.

[DeanWinchester]

The mold may not be a total loss. It might be a good candidate for paper patching or powder coating.

[Freightman]

Powder coat will add 0.0025 per coat or at least that has been my experience.

[nhrifle]

Powder coat might be an option, but to get this mould working correctly will take some work. The two halves do not line up and this is causing the boolits to be out of round. Picture the mould from the top. With the blocks together, shift one slightly more forward than the other. There is a big step on either side of the boolit rather than a faint part line. On my next mould, I may just cut a slick sided cavity since I can plunge cut that with a d-reamer with the blocks clamped and lined up, then make a grooving tool, chuck the blocks in my 4 jaw lathe chuck and lathe bore the grease grooves.

Then again, Leadman I may leave it slick sided and take you up on your offer for Hi-Tek coating, or look into getting set up for powder coating.

The new set of blocks is almost complete, and they are much better than the last. I cut vent lines in these, so fill out shouldn't be an issue. This morning I cut the slots for the handles, just have to drill and tap for the bolts and press in the alignment pins, then I will be ready to make my new cutters and cut the cavity. I will post pics of the completed blocks before I cut the cavity, and whatever tooling I come up with. Wish me luck!

[runfiverun]

actually I'd try just heating the mold up to about 425-f and re-cutting the cavity's simultaneously.
s-l-o-w-l-y.
a final polish wouldn't hurt either, and you could round things out and gain the .002 you want fairly easily too.

[nhrifle]

I have not yet decided how I am going to tackle salvaging the original mould I made, but I finished the second set of blocks a couple days ago. These are much improved over the first set and now have vent lines cut into the faces. Still working on the redesign of the cavity shape and I may go with an entirely different caliber altogether. I have been wanting a good heavy PP boolit for my Sharps and may cut that in these blocks instead. Decisions decisions!


88981

[Alphawolf45]

I want to make a mold. Where are you getting those alignment pins ?

[nhrifle]

Pins I turn to size on my lathe.

[geargnasher]

actually I'd try just heating the mold up to about 425-f and re-cutting the cavity's simultaneously.
s-l-o-w-l-y.
a final polish wouldn't hurt either, and you could round things out and gain the .002 you want fairly easily too.

That reminds me of throating a frozen barrel to get an extra thousandth at the entrance out of the reamer. Fun and games with metals.

I gotta get me a lathe, these "I made a mould" threads turn me green. But if I did get one I think my wife would either get a Sancho or divorce me, she sees so little of me as it is and I have about three lifetimes worth of lathe projects that need doing.

Gear

[Buckshot]

...........nhrifle, I assume you're using extruded aluminum rectangular barstock? I'd suggest you first install your alignment pins. You can go online and from several sources obtain seamless stainless steel tubing to use on the female side as below:

http://www.fototime.com/5F9B1C52B08A8C1/standard.jpg

I use a jewelers slitting saw to cut the tubing into 1/2" lengths. Chamfer the ID & OD of both ends. Make a tool to drive the sleeves into pre-drilled & reamed holes in the mould block. It's merely a punch with a nose to 'just' fit the ID and a shoulder of OD size. I use nominal 1/4" OD x 0.194" ID tubing. You'll also need to purchase 2 reamers. One for the tube interference fit and one for the solid pin interference fit for whatever small barstock you decide to use for the male pin. I use 13/64" as it's a nominal .203" OD. Not much metal to be removed to fit the tube's .194" ID.

Once you have the block faces faced and vented, stack them on suitable parallels in your milling machine vise. Drill & ream through the 3 spots for the smaller OD male pins, then drill and ream the top block for the tubing. Remove from the vise and drive in the alignment pins and tubing. Once that is done you can square up the ends and bottom of the blocks, and flycut the top. With that done and the pins in place, you can be assured the blocks will remain in alignment for the other operations.

You didn't say in your posts (or if you did I missed it) how you cut the cavity, but since you made a full form cutter I assume you used a double acting vise? If so you should have sufficiently deep flutes for chips to preclude opening and closing the mould blocks to clear them more often the absolutely necessary.

I actually prefer to cut mould cavities using the lathe. My lathe doesn't have a DRO so I have to use dial indicators on the carriage and compound. Since your blocks will be in the mill, if you can bore an accurate hole on center, then I'd do that and then move the blocks to your 4 jaw chuck:

http://www.fototime.com/2235C21F3A083BE/standard.jpg and center it up via a TI

running in the bore. Or to an insert vise clamped to a faceplate:

http://www.fototime.com/EC6E32186093ED1/standard.jpg or the blocks clamped between ground angleplates on a faceplate. The later 2 methods if there is more then one cavity to be bored.

http://www.fototime.com/B14C8C7293C3501/standard.jpg

I cut drive bands into this Lyman 12ga slug mould on the lathe using a faceplate. I ground an old endmill into a single tooth tool to cut the grooves.

.............Buckshot

[uscra112]

6061 alloy aluminum is not a good choice for machining anything, if it can be avoided. Much better to use 2024. If you buy an aluminum mould from the better makers, that's what it'll be. If you haven't used any yet. you will be pleasantly surprised how much better it cuts.

Being up there in hi-tech-land, you might be able to get it locally, but if not you can get small quantities of 2024 from McMaster-Carr, but I often use Midwest Metal Warehouse - http://midwestmetalwarehouse.com/

Cost is up there due to shipping, but I'm no longer anywhere near any aluminum suppliers, so I just gulp and pay the freight.

[nhrifle]

I believe the spec on the aluminum I am using is 6006 alloy, as that is what most of the products we make at work are based on. Might be something different though, it was a hunk of cutoff that I rescued from the scrap bin. It machines fairly well, but does tend to gall the cutters if pushed too much. I will look into the 2024 though.

Buckshot, I had never even considered using tubing for alignment hole liners -- thank you! Great ideas on ways to setup the parts for cutting too. My method for cutting the cavity was kind of slow and testy. I used the cutter I made like an endmill making a side cut. I mounted the blocks in my vise so the faces were toward one another and one of the sides of the blocks toward me. Zeroed the spindle on the face of one block and located the other face in relation to the first. The cutter was lowered to the chosen depth and the column locked in position. Crank up the motor, turn the X-axis handle a little at a time until the DRO read zero, indicating the centerline of the cutter had reached the face of the first block. Repeat with the second block, using the second indicated zero as my stop location.

I think this method allows for too many variables an is why the blocks didn't line up. Depending on the cavity shape I cut this time, I will use the 4 jaw on the lathe and bore the cavity true with the blocks clamped. That should be a little more accurate.

[Alphawolf45]

6061 T6 is almost as durable as 2024 and its much more corrosion resistant. I need to make a couple or three molds, still pondering over what metal I want to use. Durability, machine-ability tradeoffs. The metal is cheap enough so that price isn't a real factor for onesies and twosies.

[Buckshot]

............I use 6061-T651 alloy as it's so available and seems to machine nicely. I've never Tried 2024 but am aware it's used by most commercial & custom makers using aluminum.

http://www.fototime.com/77030C7565C1C60/standard.jpg

These cavities were cut in 6061 barstock (3/4 x 1.5") purchased from ENCO in 6' lengths.

http://www.fototime.com/EF0456293630502/standard.jpg

First drilled to remove most of the material from the cavity.

http://www.fototime.com/A0D59ED4A51A13D/standard.jpghttp://www.fototime.com/11609D54AA9989C/standard.jpg

These simple cavities were bored to size using a boring head, and the simple plunge tool in the right photo. It was a HSS drill blank. The cavities were not for boolits but for proof slugs used in proofing size dies.

.............Buckshot

[nhrifle]

A boring head would certainly make this job easier, but the limited amount of Z-axis travel on my mill would require me to find and use a very small one. I have thought about making a very small boring head, perhaps some day. For now I will make my equipment work, and I need practice zeroing a part in the four jaw lathe chuck anyway.

[Chuck_ls]

I have never made a mold that large, but it does take a few attempts to find out the size to make the cutter to get the diameter bullet you want. I think you are on the right track by making smaller cutters to take the diameter out in stages. The less the final cutter has to remove, the better the cavity will be.

Chuck

[nhrifle]

Well, I am scrapping the BMG mould idea. Noe just listed a newly produced batch and I placed an order for a three cavity. Now I just need to make or get a .512 sizer die and some gas checks. So I will be proceeding with the paper patch mould for my 45-70 Sharps. The kids brought home a cold that is kickin' my butt, so once that is dealt with I can continue with my project.

[Rangefinder]

Threads like this one are one of my favorite reasons for living at this forum. I swear--if the core of this forum were ever to just get together in one physical location for a while, considering the knowledge and experience present, the shooting world would never be the same again. Unhindered, I shudder to think about what could be accomplished. Good-LORD, I love this place...

[varmint243]

Now this is some outstanding stuff !

[nhrifle]

Feels like forever and a day since I started this project, but I was able to get the mould cavity cut this morning. After a good scrubbing and assembly, I was able to drop a few boolits. The first few came out wrinkly and gnarly, like most aluminum moulds I have used over the years. Finally, I got a keeper and tossed the bad ones back into the pot. I poured six more, as I wanted to get some pics taken and posted quickly, so here they are:

90764

The six on the bottom are the as-cast slugs, flaws and all. I am guessing I didn't get the mould hot enough or not clean enough, or that there may be some burring on the cavity edges that I missed. Whatever the problem, I am pleased with the results. They are casting with about .001" out of round, 1.5" long, and 590 grains. These should hit like a brick! They cast at .449/.450" and will be sized down to .441 before being paper patched and loaded over Holy Black. I sized one down as can be seen by the single above the others. I may make a domed punch for pushing them through my size die to give a cup base boolit.

90765

And here's my mould. The d-reamer I made cut nicely after I step drilled the cavity and it left a very nice finish. The boolits literally fall out on their own, one of the reasons I love slick-side moulds. I apparently have some things to learn about d-reamers though as I cut this one to .444" so I would only have to size down a couple thou, but it wound up cutting a bit bigger than that. Maybe a fluted reamer would cut better, who knows?

As long as this boolit is, I may have to get a 45-110 in the future.