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Thread: Annealing B7 Rod for making dies

  1. #1
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    Annealing B7 Rod for making dies

    To make a long story short, I have purchased some 7/8 14 threaded rod for making die sleeves that I thought was mild steel but turns out to be B7 steel. I can machine it but I cannot cut internal threads in it. So, my plan is to anneal the rod (after cutting into die length chunks). I am on a very tight budget and cannot afford to build even a cheap gas forge. So I have been looking into the feasibility of using a charcoal forge for annealing this rod (I also have a bunch of bowman 7/8 14 bolts that I would anneal if I could. I know that it is not the best to be chucking threaded rod into a lathe but I have found that if I use an aluminum sheath around it and not re-chuck it, it is good enough for my work.
    Do any of you have experience with annealing threaded rod? Is it something that can even be done on a charcoal forge? My plan was to try and do as many chunks at once as I can and just let them cool with the cooling of the forge after stopping the blower. Hopefully this would give me the slow cool that is recommended.
    The dies that I make are just for lead boolits, making the dies for jacketed bullets is beyond my skill level.
    Thanks for any and all info.

  2. #2
    Boolit Master
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    Slow cooling in charcoal forge sounds like it should work just fine. Do you have an actual forge? OR, do you plan to rig something up using a vacuum cleaner for blowing to get the heat? You say this is for lead bullets - are you swaging lead bullets?

    I'm going to tag this thread so I can see how it turns out so be sure to post results.

  3. #3
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    I wouldn't do it. The small cross sections of the rod in the threads will lose carbon. Plus it will come out black and nasty. A better tact might be to cut your rod to usable lengths and see if someone here will put it in their benchtop kiln. That will keep it clean and other than for the cost of postage be pretty cheap.
    Zbench

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    I would just buy some threaded rod from the correct steel. A foot is about $6.

  5. #5
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    You should be able to do this with charcoal or coal even hard wood may do it. Tempering is time and temp then slow cool. Using charcoal coal or wood you may increase the surface carbon levels. Oxidation in the fire is going to happen do to oxygen and other impurities being present. Your probably talking 1500-1800 degrees to anneal with a slow cool down, here more pieces is better as it increases mass and helps slow cooling. I believe after the initial annealing up to temp and soak I would add charcoal to top and let burn down slow for several hours.

    As to the threaded rod there may be some warpage of the threads when annealing but on most threaded rods there is enough thread clearance to still be useable. If you have drilled the holes already I would be more concerned with the pieces warping and bowing or going egg shaped. You will need to clean the oxidation from threads before using. We left big threads .015 large if heat treated and recaught them in the lathe to finish them after heat treat. Gage threads were ground in to size sometimes lapped depending on tolerance fit required. A simple split brass die can be made to clean up the threads after annealing. a round piece of brass 1" long or so drilled and tapped 7/8 14 a nice chamfer on each end split on center and drill and tap hole to close it as needed. coat with fine lapping compound and run over threads back and forth with some light oil. this will clean up the threads and give a smooth finish.

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    Quote Originally Posted by KenH View Post
    Slow cooling in charcoal forge sounds like it should work just fine. Do you have an actual forge? OR, do you plan to rig something up using a vacuum cleaner for blowing to get the heat? You say this is for lead bullets - are you swaging lead bullets?

    I'm going to tag this thread so I can see how it turns out so be sure to post results.
    I was planning on using the guts of a cheap electric leaf blower and substituting a DC motor so I can easily control the speed. I have a 4 ft length of 2 1/8" flexible tail pipe that I can use for the air pipe. I haven't decided exactly how to make it yet. Probably with fire brick and sand. There are lots of good ideas on youtube. A place here sells the big fire bricks for $2.75 apiece. I live in an apartment so I have to find someone that will let me build a small forge in their back yard. That will probably be the hardest part of the whole thing.
    I swage lead bullets. So far only 22lr. These require both a rebated base and a hollow base. So it is a challenge to make the dies right. I designed them to join at the place on the bullet that is the largest diameter. That is just at the end of the rebate area. So I have a base die that swages the hollow base and rebate, and a point forming die that swages the point and ogive down to the rebate. I worked out a way to make the union concentric and the spot where the excess lead squeezes out and gets cut off. It took 3 years to perfect but I have it working well now. These are also powder coated before swaging. Here is s picture of some of the colors I tested (there is one factory cartridge in there for comparison.) You may notice that I did not make these with a "step" in the ogive like commercial ammo. After doing some research I came to the conclusion that the step is there because the factories join their dies at that union using a 3 piece die. Otherwise it is a hindrance to performance. Since I use the 2 piece die which joins at the base I designed mine without the step for better stability.
    Attachment 225741

  7. #7
    Boolit Master
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    To avoid scale, warping, loss of carbon wrap the lengths of rod in multiple layers of a clean paper or pure cotton cloth. Place the wrapped rods in a section of black iron pipe with threaded end caps, filling the space between the rods and the pipe with charcoal. Put small vents in the end caps 1/8" hole in each end. Heat the pipe in the coals until it is orange, hold the orange temperature of the iron pipe for 15-30 minutes, (DO NOT melt the pipe) turn off the blower and let things cool. Rod inside pipe should anneal without surface damage or warping.

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    Quote Originally Posted by MostlyLeverGuns View Post
    To avoid scale, warping, loss of carbon wrap the lengths of rod in multiple layers of a clean paper or pure cotton cloth. Place the wrapped rods in a section of black iron pipe with threaded end caps, filling the space between the rods and the pipe with charcoal. Put small vents in the end caps 1/8" hole in each end. Heat the pipe in the coals until it is orange, hold the orange temperature of the iron pipe for 15-30 minutes, (DO NOT melt the pipe) turn off the blower and let things cool. Rod inside pipe should anneal without surface damage or warping.
    I was thinking of some type of container. Thanks, you just answered this one for me.

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    Quote Originally Posted by MostlyLeverGuns View Post
    To avoid scale, warping, loss of carbon wrap the lengths of rod in multiple layers of a clean paper or pure cotton cloth. Place the wrapped rods in a section of black iron pipe with threaded end caps, filling the space between the rods and the pipe with charcoal. Put small vents in the end caps 1/8" hole in each end. Heat the pipe in the coals until it is orange, hold the orange temperature of the iron pipe for 15-30 minutes, (DO NOT melt the pipe) turn off the blower and let things cool. Rod inside pipe should anneal without surface damage or warping.
    Wow Thanks, Glad to hear it is possible and really not that hard. I have a piece of 3" black pipe but not threaded. Maybe weld something on one end and figure out how to plug the other. It's hard to do a new project without a good picture of it in your mind. Thanks to you I can clearly see what needs to be done now.

  10. #10
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    Try this, it won't get you to dead soft but it will take you into the spring temper area so you can cut it. Preheat with a propane torch until boric acid will melt on it, this seals out oxygen. Then you can wrap in paper then stainless steel foil. Put in your kitchen oven, when SWMBO is not home, put the oven into the self clean cycle for a couple three hours and let cool off till dead cold, probably overnight. Clean up with water or wire wheel and you are now down into the workable softness range.

  11. #11
    Boolit Master

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    IMHO it should not be SUPER hard to begin with ?? 4140 pre heat treat is 28-32 rockwell C ??

    4140 ASTM A193 Grade B7 Alloy – Similar to 4140 alloy, but it’s already quenched, tempered, and stress relieved. Rockwell hardness is C35 max.
    found this...

    Unless there's some reason for a full anneal, the safest thing to do is a subcritical anneal. On most any med carbon alloy steel you can bring it up to about 1400* and hold it for a couple hours and end up with a Brinell slightly over 200. On a subcritical anneal the part can be pulled from the furnace and air cooled without problems because there is no austenite formed and therefore nothing to transform.
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    What shade of orange would 1440 degrees be in low light?

  13. #13
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    Quote Originally Posted by Traffer View Post
    What shade of orange would 1440 degrees be in low light?
    http://www.blksmth.com/heat_colors.htm

    Interesting info there....1500 is "unfanned coals of a wood fire". The proper type K thermocouple (with a lead rated at the temperatures needed) will go to 2300 F. I see a few on Ebay, search "High Temperature K-Type Thermocouple Sensor Ceramic Kiln Furnace ".

    Type K at 782 C 1440 F) would put out 32.536mA
    https://www.thermocoupleinfo.com/typ...ermocouple.htm

    Bill
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    I would suggest using some of the Brownell's non scaling compound to protect the surface and give one or two pieces a try by heating with a propane torch, use a digital temperature gun to monitor temps. You may find that B7 is not at all what you want to work with.
    Got a .22 .30 .32 .357 .38 .40 .41 .44 .45 .480 or .500 S&W cylinder that needs throats honed? 9mm, 10mm/40S&W, 45 ACP pistol barrel that won't "plunk" your handloads? 480 Ruger or 475 Linebaugh cylinder that needs the "step" reamed to 6° 30min chamfer? Click here to send me a PM You can also find me on Facebook Click Here.

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    Taffer, somewhere you mentioned needing to set up a temporary forge.
    Maybe go camping.
    Take a couple bags of charcoal, some fire brick to make natural aspirated forge in the fire pit.
    Put the steel you want to anneal in a "pipe bomb" keep adding charcoal. Quaff some beverages. Use the excess heat to cook some hot dogs. Stay up late and keep adding charcoal so the heat can soak all the way through your steel.
    Fish your annealed steel and fire brick from the fire pit in the morning.
    To lazy to chase arrows.
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    Quote Originally Posted by Willbird View Post
    http://www.blksmth.com/heat_colors.htm

    Interesting info there....1500 is "unfanned coals of a wood fire". The proper type K thermocouple (with a lead rated at the temperatures needed) will go to 2300 F. I see a few on Ebay, search "High Temperature K-Type Thermocouple Sensor Ceramic Kiln Furnace ".

    Type K at 782 C 1440 F) would put out 32.536mA
    https://www.thermocoupleinfo.com/typ...ermocouple.htm

    Bill
    Thanks for those links. Wow, for someone like me this information is like GOLD. I have had difficulty wrapping my mind around thermocouples and the link helps a lot. And the color chart with the added information is a reference that would help me learn about heating steel. Thank You!

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    Quote Originally Posted by clodhopper View Post
    Taffer, somewhere you mentioned needing to set up a temporary forge.
    Maybe go camping.
    Take a couple bags of charcoal, some fire brick to make natural aspirated forge in the fire pit.
    Put the steel you want to anneal in a "pipe bomb" keep adding charcoal. Quaff some beverages. Use the excess heat to cook some hot dogs. Stay up late and keep adding charcoal so the heat can soak all the way through your steel.
    Fish your annealed steel and fire brick from the fire pit in the morning.
    That's a great idea. Thanks. I may not do the camping thing but this is something I might talk a friend into letting me do in their back yard sometime.

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    Quote Originally Posted by DougGuy View Post
    I would suggest using some of the Brownell's non scaling compound to protect the surface and give one or two pieces a try by heating with a propane torch, use a digital temperature gun to monitor temps. You may find that B7 is not at all what you want to work with.
    You are right about B7 not being a good choice of material. The problem is I bought this stuff thinking it was mild steel and I need to be able to use it because of the expense. I have made too many purchases lately that turned out to be wrong ...I have to recoup what I can from these fiascos. This "hobby" is starting to seriously hurt our budget.

  19. #19
    Boolit Master

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    Quote Originally Posted by Traffer View Post
    Thanks for those links. Wow, for someone like me this information is like GOLD. I have had difficulty wrapping my mind around thermocouples and the link helps a lot. And the color chart with the added information is a reference that would help me learn about heating steel. Thank You!
    Thermocouples are not TOO bad, just remember that the red wire is common (-) and the black wire is hot (+)...engineer at work told me people wire them up backwards a lot.

    RTD are another temperature sensing device, rather then generating electricity an RTD is a resister whose resistance value changes with temperature.....they are around 110 ohms resistance at 75 degrees.

    There are a bazillion materials out there.....stressproof is another one you may wander across, it is a work hardened material.....not the same but same general idea as 4140 pre heat treat, a material soft enough to machine but with a hardness and temper to make it strong...lots of old timers will mention stressproof.

    Bill
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  20. #20
    Boolit Master
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    Somewhere out there is a color chart of steel at the various temperatures (Google)

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