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Thread: Jacket forming dies: disc blanking punch and die

  1. #1
    Boolit Mold
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    Jacket forming dies: disc blanking punch and die

    Thought it would be a good time for update on the jacket forming project. Just got back from heat treatment my disc blanking punch and dies. Since my last post I have made lots of design changes including new die bodies with threads that screw into a die plate. While doing this I also used the same footprint to make the disc punch and die. I chose in the end to use a 1 inch disc because I got good results with the prototype tooling. Die and punch was machined in 4140. The die was nitrided to about 58 rockwell C and the punch was through hardened and tempered to about 54 rockwell C.
    The design of the die uses two symmetrically identical blocks that create a clamshell when mated. I used roll pins to secure the two halves. Each block has a milled step half the thickness of the copper strip. When joined, they form a slot for the strip.
    The big difference to my prototype punch was the inclusion of a 1.5 degree shear angle on the face. This has had a huuuuuge reduction in the required force needed on the arbor press. Its now an easy 25lb of elbow grease (I'm using a 2' bar on the press). The end result looks pretty good. Just need to make an indexing stop to minimize the gap between each cutout on the strip.
    More posts on the way. Just waiting on some parts from heat treating and should then be able to do a small run.
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  2. #2
    Boolit Master



    MUSTANG's Avatar
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    Will be following. Keep up the excellent overview.
    Mustang

    "In the beginning... the patriot is a scarce man, and brave and hated and scorned. When his cause succeeds, the timid join him, for then it costs nothing to be a patriot." - Mark Twain.

  3. #3
    Boolit Buddy
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    Also following,,keep us updated please.

  4. #4
    Boolit Mold
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    Thanks mustang & rcslotcar. Happy to report that I punched out about 50 discs and set up the press to cup and first draw. The first big difference I noticed from my prototype tooling is that the quality of the cups have gone up considerably. I put it down to a few things. The discs are nearly burr free and nest in the cup die more accurately. I'm now using a lot less lubricant (now straight castor oil), so just the lightest smear does the job. These changes also carried across to the first draw. I'm now measuring the differences with dial indicators on both runout and wall thickness variation. Big improvement with some first draw jackets at about .0004" runout. One really obvious way to see improvement on the jackets is the top where a "crown" forms. The flatter and more even the crown the better the runout.
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  5. #5
    Boolit Mold
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    Some more pics of the cups and first draw jackets
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  6. #6
    Boolit Master Traffer's Avatar
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    Beautiful work. Have you ever considered making drawing dies for forming primer cups?
    Here are some files that I found that may be of interest to folks making drawing dies:
    https://www.dropbox.com/sh/kt5zuafbp...ADnIBObaa?dl=0
    Module 8 is about cup drawing.

  7. #7
    Boolit Mold
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    Hi Traffer, I'm just out to concentrate on one thing...making a .264 bullet for my favorite rifle. I've read a fair bit on deep drawing but always happy to find out more...thanks for the link.

  8. #8
    Boolit Master
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    What tonnage /size/model is that arbor press?
    NRA High Master XTC
    DR# 2125

  9. #9
    Boolit Buddy
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    Andrew, your progress looks great and good idea about adding an angle to help with the cutting. Can I ask how large in diameter is your disc? I have been contemplating trying to use US pennies (pre 1982) to attempt to draw out a jacket since these are 95% copper. This might work if they are properly annealed but I am not sure.

  10. #10
    Boolit Mold
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    2 ton optimum brand 8" stroke

  11. #11
    Boolit Mold
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    Quote Originally Posted by plus1hdcp View Post
    Andrew, your progress looks great and good idea about adding an angle to help with the cutting. Can I ask how large in diameter is your disc? I have been contemplating trying to use US pennies (pre 1982) to attempt to draw out a jacket since these are 95% copper. This might work if they are properly annealed but I am not sure.
    I'm using 1 inch discs 0.027 thick C12200 copper. To give you an idea of the required tonnage, I used an online calculator to work out tonnage required for a flat faced punch and a punch with shear angle.Click image for larger version. 

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  12. #12
    Boolit Mold
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    Just got my 2nd and 3rd draw dies back from heat treatment. They are also 4140 nitrided to 60HRC. They have been machined undersized so I've been lapping the 2nd draw die to size. This die can also be used for .308 jackets so I want a final size under .305. They came machined at .302 so I had to make lapping mandrels to suit. My way is a bit odd but the results seem to work. First I run a jacket through the die as is. This jacket is then placed in a ER collet holder and used as the lapping mandrel. Using a 1200 grit lapping paste, the die is rotated by hand on the mandrel. When this becomes easier and looser, I then run another jacket through the slightly enlarged die. Repeat until final size is met. This case the jacket comes in about .30480. I finally ran all the 1st draw jackets through and just checking final sizes. Runout is good at under 0.01mm/.0004". Not quite J4 but close. Pics show the mandrel lapping method and some of my measuring gear. I'll attack the final .264 draw die this weekend. Note: most of my measuring equipment is metric....that's an Australian thing.

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  13. #13
    Boolit Buddy M.A.D's Avatar
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    For your future lapping endeavors...http://www.acrolaps.com

  14. #14
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    Still continuing to impress. Keep up the great work and the updates please.

  15. #15
    Boolit Mold
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    Thanks M.A.D and MrWolf. I had a look at the acrolaps website...nice product. Do you know if there is an agent here in Australia? A couple of barrel laps near .300 and .260 would be handy.

  16. #16
    Boolit Mold
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    I finished lapping the final .264 draw die over the weekend. Happy with .26080" as the finished diameter. Just a fraction under .261". Not only did I run a batch of jackets through but also used the pinch trim die I had machined up. This die is adjustable for jackets from about 0.9" to 1.42". This will allow for a nice flat base projectile around 90 grains to a boat tail around 140 grain. The design uses two punch parts. First operation is a flaring insert that fits on the punch. The second operation is the punch which is stepped cuts the OD jacket diameter and passes through the die pushing the jacket through to eject it. This is a bit different to the Corbin style which uses a flared face punch on a perpendicular die face. The final check on runout has it still within .0004". Can't be more happy with that. I have been now talking to Brian at BT Sniper for set of his swaging dies and hopefully will have a set on order soon. Now I'm doing heaps of reading up on the pointy end of bullet making. Can't wait to swage up my first .264 bullets. I own an old Tikka 695 with a stainless Benchmark barrel in 6.5x55. This rifle shoots sub 0.3" groups with ease and would love to feed it with a home grown bullet.

  17. #17
    Boolit Mold
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    Some pics of the .264 jacket being drawn then trimmed.

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  18. #18
    Boolit Man
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    Im assuming uniformness all comes down to the material your using. Im thinking it would be hard to get them as accurate as say J4 or Hynes jackets.

    Very interesting though.

  19. #19
    Boolit Mold
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    Hi TrxR, It is really hard to get them as accurate as J4 or Hynes. My goal was to get a jacket as accurate as possible with a modest budget and resources. I'm really surprised that I have gotten this close considering I am still learning as I go along. Most of the work I've done to increase runout and wall thickness consistency has been around punch and die concentricity. If there is a tiny amount of punch wander during the downward stroke it will show up. I looked at the weakness of traditional 7/8" dies and designed a version that has a cone shoulder. When tightened into the Die plate they pull in to true center. To calibrate the punch and die plate center I made a dummy die that has a machined inward cone. To set up, I loosen the die plate screws, bring the punch down into the inward cone firmly and then tighten the screws on the die plate. Now I know the punch is centered to the die. This set up has really improved the consistency of the jackets.

  20. #20
    Boolit Mold
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    Close up of the dies. Thread is a M25x1.5 and 2mm cone shoulder. This allows the die to center in the die plate eliminating alignment error

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BR Bench Rest M Magnum RN Round Nose
BT Boat Tail PL Power-Lokt SP Soft Point
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