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Thread: Lathe boring a minie ball mould

  1. #1

    Lathe boring a minie ball mould

    Maybe I am being too ambitious!

    I center a set of BRASS mould blocks in a 4 jaw chuck on my lathe.

    Then I start by using a 1/4 inch drill to drill ALL the way through the blocks. Of course, where the drill comes out of the blocks will be the top of the mould and will be where the sprue plate will be installed when the mould is finished.

    Then using larger drills, up to a 1/2 inch drill, I remove most of the brass from the future mould cavity.

    Then I stick in my "reamer blade" which has the outline of the ogive of the bullet and also the grease grooves. Turning at 600 RPM I move the tool post, allowing the "reamer blade" to enlarge the cavity.

    I use a dial gague to keep track of how much I have moved my tool post and stop when I figure that my mould cavity has been enlarged by the reamer blade to .575 which is the size of the cavity I want.

    Unfortunately, this method is slow. Failing getting a CNC lathe-is there a better way to make a lathe bored bullet mould cavity?

    Any Advice Will Be Greatly Appreciated!

  2. #2
    Boolit Master JIMinPHX's Avatar
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    Aug 2007
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  3. #3
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    Buckshot's Avatar
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    Mar 2005
    So. California
    ...............So you've ground yourself a 'spoon', eh? That's not the only way to lathe bore, but they're simply variations of the theme. Basically it's using more then one tool to create the cavity. For large caliber cavities (and especially short ones) your single profile tool should be rigid enough to do a good job. Using drill bits to hog out the majority of metal is the smart way to go. It's also much simpler if your lathe is fitted with a DRO. Mine isn't so I have to jury rig DI's to read on the compound, cross slide, and carriage.

    For multiple tools on a manual lathe, each has to be zero'd to a common recorded reference you can work from. Using your example of boring for a Minie', as you mention you drill out the bulk of material first. Your first form tool would bore the minor diameter (what will be the bottoms of the lube grooves) as it's fed in, and possibly partially form the nose profile to eliminate some of that material.

    The next tool in could be the one to cut the drive bands to full OD. The final tool would be the nose profile finish tool. The negative to multiple tools without a DRO is Knowing where they are" and you're reduced to recording their initial zero's for later reference on paper and working from that. It can be confusing, and requires care. The main possitive to multiple tools is that since they are each responsible for a smaller area, they can be much more rigid.

    Secondarily multiple tools, unlike a single complete profile tool may be used for other designs such as fewer or more lube grooves. Also other tools can be substituted in various combinations.

    Some forming tools I've made up. The one on the right was for making a Pritchit style (no lube grooves) Minie' swage die.

    Last edited by Buckshot; 06-30-2010 at 02:10 AM.
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  4. #4
    Boolit Master

    theperfessor's Avatar
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    Dec 2007
    Evansville Indiana
    Don't know if this is may be helpful:

  5. #5
    Boolit Master Doughty's Avatar
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    Jun 2005
    Missoula, Montana

    At the end of your original article, you talked of some refinements that you wanted to explore as you had time in the future. Well, some of the future is here. I am wondering if you have found time to complete any refinements, such as a one pass venting tool? Did you make your 5 cavity slug mold of .250 through .500? If so I would sure like to see what the results are. (If you made them long enough, the pure lead slugs would be good for swaging neck/throat/leade areas.)

    Also, your "C bar" clamp? Do you use that just when you're setting your blocks, or do you keep it in place while you're actually cutting cavities?

    Any new bullet designs?


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  6. #6
    Boolit Master

    theperfessor's Avatar
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    Dec 2007
    Evansville Indiana

    I don't want to create a massive thread drift here, so I will post an update/progress report in a couple days in a new thread.

    Short story, I have made a number of improvements in my processes and equipment in the last couple years, and I just finished three 5-cavity test molds. Details to follow. Thanks for interest, I will address your questions.

    Southron -

    I wish you success in your efforts, making your own molds can be a very satisfying endeavor.

  7. #7

    Now, it is time to get back on the lathe to try some of the things I have learned in the above posts!


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Abbreviations used in Reloading

BP Bronze Point IMR Improved Military Rifle PTD Pointed
BR Bench Rest M Magnum RN Round Nose
BT Boat Tail PL Power-Lokt SP Soft Point
C Compressed Charge PR Primer SPCL Soft Point "Core-Lokt"
HP Hollow Point PSPCL Pointed Soft Point "Core Lokt" C.O.L. Cartridge Overall Length
PSP Pointed Soft Point Spz Spitzer Point SBT Spitzer Boat Tail
LRN Lead Round Nose LWC Lead Wad Cutter LSWC Lead Semi Wad Cutter
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