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Thread: Making bullet molds

  1. #1
    Boolit Bub acoilfld's Avatar
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    Making bullet molds

    Found this link on Google. It is a 66 page word document describing how to make bullet molds. Lots of good pictures in it also.
    http://www.usi.edu/Science/engineeri...ulletMolds.doc

    The link gives you the option to either open or save the document.
    I found it interesting and thought that I would share it.

    AC

  2. #2
    Boolit Master




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    acoilfld
    thanks for putting it up for us to see. Very interesting reading
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  3. #3
    Boolit Master


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    I think that was written by our member "The Professor"

  4. #4
    Cast Boolits Owner


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    I believe that article was authored by fellow forum member "theperfessor". I am sure if you have any question he would be more than happy to answer them.

    Robert
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  5. #5
    Boolit Grand Master

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    I have admiration for machine tools and those with the knowledge to achieve the most out of them.

    Wonderful article !!

    SHiloh
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  6. #6
    Boolit Bub acoilfld's Avatar
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    I assumed that it was OK to link to this since it was posted on Google.
    If I would have known how to contact him first I would have.
    As it is - I would like to thank him for the article that he wrote, It answered a lot of questions that I had about the process.

    AC


    EDIT:

    I tried searching for "The Professor" on this site (to let him know that I linked to his site) - but could not find him listed.
    Last edited by acoilfld; 01-28-2010 at 10:09 PM. Reason: additional information

  7. #7
    Boolit Master

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    No problem with the link. I think the original thread is in the Classics and Stickies section now. Glad to hear you enjoyed it.

    I'm still improving tooling and developing knowledge base to make custom multi-cavity bullet molds to my standards.

  8. #8
    Boolit Buddy robroy's Avatar
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    acoilfld and Professor, ThanksI coppied the document and saved it to my desk top. Professor If I ever get a lathe and a mill I'm gonna steal your fixture design. By then you'll have the bugs workedm out and I'll still have the old design.

  9. #9
    In order to have better control of as-cast bullet diameter, I plan to make two five-cavity molds, one each of 7075 and 2024 aluminum, with drilled and reamed cylindrical cavities with diameters of ¼" (0.250"), 5/16" (0.3125"), 3/8" (0.375"), 7/16" (0.4375"), and ½" (0.500"). This covers the range of possible mold diameters I am interested in. I will get the molds up to proper casting temperature and use pure lead, recycled wheelweights, linotype, and other alloys of interest to cast slugs that I can measure and compare to the cavity size to get empirical data on the amount of actual shrinkage with each alloy in a mold of a certain composition.
    I would like to ask the author of that article, theperfessor, if he ever completed this and what his results were. I would be very interested in them. I would especially like to know if shrink ratios were also effected by the depth of the cavity.

  10. #10
    Boolit Master

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    I'm using my iPhone right now so I will keep this short and simply say that I will give update on this tonight when I get off work.

  11. #11
    Boolit Master


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    Quote Originally Posted by theperfessor View Post
    No problem with the link. I think the original thread is in the Classics and Stickies section now. Glad to hear you enjoyed it.

    I'm still improving tooling and developing knowledge base to make custom multi-cavity bullet molds to my standards.
    A DRO would be a big help, you have a big challenge with manual machines even if it is a Monarch 10EE.
    The biggest problem I see is measuring the ID of the cavities.

    Has any members checked the variations of the weights between the cavities on LEE molds? They are lathe bored on CNC machinery. CNC machines are supposed to be able to hold .0001" accuracy or more given the right environment.

  12. #12
    Quote Originally Posted by deltaenterprizes View Post
    A DRO would be a big help, you have a big challenge with manual machines even if it is a Monarch 10EE.
    The biggest problem I see is measuring the ID of the cavities.

    Has any members checked the variations of the weights between the cavities on LEE molds? They are lathe bored on CNC machinery. CNC machines are supposed to be able to hold .0001" accuracy or more given the right environment.
    A manual lathe with old fashioned dials will hold .0001" if the right person is running it. CNC eliminates most of the human factor.

    If coolant temperature changes, or machine temperature varies, it's pretty easy to go over a .0001" tolerance. It can change that much between parts due to cutter wear. .001" is much more realistic outside a highly controlled environment and other factors.
    Machinists do it with precision.

  13. #13
    In Remembrance


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    Enjoyed that! Thanks Perfessor.

  14. #14
    Boolit Master


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    Quote Originally Posted by machinisttx View Post
    A manual lathe with old fashioned dials will hold .0001" if the right person is running it. CNC eliminates most of the human factor.

    If coolant temperature changes, or machine temperature varies, it's pretty easy to go over a .0001" tolerance. It can change that much between parts due to cutter wear. .001" is much more realistic outside a highly controlled environment and other factors.
    The manual machine may be able to hold .0001'' but .001'' to .0005'' about the best I can do on a good day!

  15. #15
    Boolit Grand Master JIMinPHX's Avatar
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    Tolerances vary with the machine, the machinist, the tooling, the operating environment & the time available. There are a lot of places that you can loose more than a tenth.
    “an armed society is a polite society.”
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  16. #16
    Boolit Grand Master

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    Lee molds are no longer bored on a lathe. Pat told me last week that they are using a milling machine now. The molds halves are not closed and are cut seperately. Must be something like MiHec is doing.

  17. #17
    Boolit Master

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    Let me answer some specific questions and issues raised in some of the posts here.

    deltae-
    Just as you mentioned, I realized I needed to improve the positional accuracy of my lathe, and I needed better inside measuring tools. I had the local guy that I buy all my tooling from install a DRO on my 15 x 48 Clausing Colchester lathe. I really love the Newall unit. (Picture 1) The axes readers are hollow aluminum tubes filled with steel balls. They're completely sealed, no gears or glass scales. The pickup unit just slides over a smooth tube and reads position by magnetic induction through pickup coils.

    The new units have all the mill and lathe functions built in, so the same display/control unit can be used on mills or lathes. It will store offset values for up to 99 tools, so I can program in a unique position for each tool. It lets you use built in functions, such as locating points on a line or an arc, to generate coordinates to "step cut" curves and arcs. I can hold 0.0005" to 0.001" on diameters between tool changes fairly easily with this.

    I have always used small holes gauges with an outside micrometer to measure small holes. (Picture 2, 3, and 4) These things come in sets that typically run from 0.125" to 0.500". They have a reverse taper plug on a threaded stem that spreads the leaves apart when the knurled handle on the end is turned. Put the gage in a hole, turn the handle until you get a light feel, pull out the gage and measure across the leaves with the same feel on your mike. I can easily fit things together to 0.0005" accuracy this way, since the same mike is used for both measurements, canceling out any calibration errors.

    I also use inside micrometers. (Picture 5 through 8). The two shown here cover a range of 0.200" to 1.000" and 1.000" to 2.000" They come with a ring gage as a calibration standard.

    The trouble with both of these methods is the inability to measure the diameter of a hole that is larger than the hole connecting it to the side accessible to a measuring tool. I bought a special tool designed primarily to measure the diameter of snap ring and O-ring grooves. Its a digital spring caliper. (Picture 9) It can be calibrated to a specific size with a mike or ring gage to read absolute size (say 0.358"), or it can bet set to zero at a certain size, and it will then read the tolerance, or how much bigger or smaller the hole is (+/-) from the perfect size. Both modes can be useful. The tips are small enough to read a narrow groove, and the diameter and length range cover any bullet size I would make a mold for.

    robroy-
    Don't mind you copying design. But don't just take it, improve it. Make it work for you. I have moved a couple of pieces so now I can make 5 cavity molds for anything .40 to .50 caliber and 6 cavity molds for .30 to .40 caliber.

    tommygirlMT-
    I wanted to determine shrinkage characteristics of various mold materials and alloys. I knew that I would have to be able to measure and control the temperature of my lead pot and bullet molds, so over the Christmas break I built a dual PID controller. Here is the thread on that:

    http://www.castboolits.gunloads.com/...ad.php?t=71208

    I have prepared a batch of 12 bullet molds that are ready to have the cavities cut. Five of them are 7075 aluminum, five are 2024 aluminum, and two are Dura Bar malleable iron. Now that I have the equipment and tooling issues under control, and a way to accurately measure things, I am ready to cut my five cavity test molds using one of each material type. It will probably be a while before I can get to them , because I am heavily involved with a number of student and other personal projects right now, but it will happen and I will report the results on this site.

    Along the way, a topic was raised in another thread concerning the observation that too-hot molds cast smaller bullets. My original objective was simply to determine the proper minimum melt temperature to use to get good fillout, but I realized that I could address this issue as well by broadening the test parameters (temperature range), so I plan to address this also. In any case, it will generate enough empirical data that I can use to determine the recommended "best" melt temperature to use with my molds.

    machinisttx-
    I'll go with your 0.001" as a practical figure. Anything closer than that I sneak up on, hand fit, or find a better process!

    Thanks again to all for your interest and kind words.
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  18. #18
    Boolit Master

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    I keep turning the idea over about making a set of mold blocks from EDM graphite
    Both ends WHAT a player

  19. #19
    Boolit Master

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    Other than high temperature resistance, what qualities does EDM graphite have that would make it better than what is being used now?

    I'm surprised that somebody hasn't tried making bullet molds using powdered metal/sintering technology.

  20. #20
    Boolit Master

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    Well it machines pretty easily was what brought it to mind. The mental wandering went to things that have a lower coefficient of expansion (like TI) but are difficult to machine. The cats meow might be a set of "master" blocks that can have some slabs of the graphite bolted to them, the master blocks would have the machining for the handles, and maybe even the sprue plate. Then all the graphite is doing basically is providing the cavity.

    Carbide would be a good material too, it can be machined in the "green" state, then it gets some kind of final process (involving high heat I'm sure) that makes it into what we know as carbide. I have never machined it but heard from more than one person that they had done so. I have ground a lot of carbide, and it is very nice to grind using the proper equip and wheels, you can rip it off as fast as you want and it never heats up and swells like steel does when you try that.

    I'm interested in paper patch molds lately, and those especially would be readily done in carbide because there are no grease grooves, it is all ID grinding. I wish I still worked in the shop where I learned all that stuff .

    Plain old 12L14 might make good mold blocks.

    Bill
    Both ends WHAT a player

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