DIY annealing machine

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    • #3869
      Bob Walters

      By Bob Walters
      If you believe that reloading consistency is one of the keys to achieving high match scores, then you have probably considered annealing your brass. However, you may have been put off by the high price of commercially available machines or by the obvious inconsistency associated with makeshift hand held methods.
      However, there is a way to anneal your brass using a machine which is second-to-none and without spending too much money; built it yourself.
      Part of my formal education included a couple of courses in metallurgy where I learned a little bit about brass. It behaves quite unlike steel. Cartridge cases expand and contract during the firing process. Cases experience further deformation during the resizing and bullet seating process; no surprises there. Cumulative distortion like this causes what is known as “work hardening”. The result is that the soft, ductile brass (especially in the neck area) becomes harder, less ductile, stronger, and more elastic (more springy, so to speak). Eventually, the case becomes so hard and brittle that it is subject to cracking. Most of us have experienced this phenomenon first-hand in the form of cracked cartridge necks.
      The work hardening process can be reversed by heating brass to a sufficiently high temperature for a certain length of time; it is called annealing. Changes in the grain structure start at just below 500° but annealing at 500 degrees takes a long time. At 650F or so, a cartridge can be annealed in several minutes. But for our purposes, we normally heat the case neck to around 750° for five seconds or so. The exact time depends on the neck thickness and the temperature of the heat source, normally one or two ordinary propane torches with a pencil tip nozzle.
      Why not anneal cases in a home oven for a few hours? Because we do NOT want to anneal the cartridge base. It should remain in the hardened (read “strong”) condition which is a by-product of the factory forming process. Subjecting the main body of the case, and particularly the base, to annealing temperatures is a real no-no and can be dangerous. The solution is to heat just the neck and shoulder area to a relatively high temperature for a relatively short period of time. If the case is removed from the flame at the proper time, any residual heat conducted down the case body will not result in any softening or weakening of the cartridge base simply because the main body of the case wont’ reach the annealing threshold. Below about 450° F, you don’t have to worry about damaging your cases.
      If you are interested in knowing more about annealing, Google is your friend. Caution, not everything you read on the Internet is the whole truth, but you already know that.
      The features of a good annealing machine include low cost, high reliability, precision repeatability/consistency, easy adjustability, a hopper that can hold a hundred or more cases, a method for automatically feeding the cases to the annealing station, small size, portability, and perhaps a few bells and whistles.
      An Australian shooter named Skip invented and perfected what has become known as the “Skip Design” annealing machine. Even though Skip sells these machines in Australia now, he is generous enough to have published everything you need to know to construct your own version. A great many DIY enthusiasts have built a machine and as far as I can tell, they have enjoyed nearly universal success. Rather than try to detail the design and evolution of this machine, I recommend you read this thread on the AR-15 forum:
      If you’re more than curious and plan to actually build an annealing machine, I strongly encourage reading every post in this very long thread. It is loaded with hints and tips, plans, dimensions, parts list, supply sources, and all sorts of good information. Yes, it’s long, but well worth the time to read the entire thing.
      The basic design is based on a simple box to house the components. Inside is a power supply, a motor driving the feed drum, a second motor driving the annealing pan, and a pair of speed controllers, one for each of the motors.
      Here are some EBay links to the three major components:
      Speed controller:
      Power supply

      These parts typically cost less than ten bucks each and arrive from China in 10 days or so.

      Look at my machine to get an idea of the basic layout.


      Let’s consider some of the design features. The feed drum can be made from a wooden dowel, a hard plastic rod, or a piece of aluminum. It has a groove a bit larger than the cartridge case. As it rotates, it picks up a case from the feed hopper and dumps it onto the feed ramp.

      From there the brass rolls down to the “waiting position, where it rests against the outside edge of the rotating annealing pan. The pan is fabricated from a small aluminum cake pan. I got mine at Hobby Lobby. Look for one with straight sides. The pan has a cutout and when it aligns with the feed ramp, the case drops into the pan. The case comes to rest against a steel stop rod positioned so that the neck is in the flame of the propane torch. As the pan rotates, the case spins so that it heats evenly. The next time the notch comes around, the case falls into a collecting pan where it is allowed to cool naturally. By the way, unlike steel, quenching brass has no effect on the hardness.

      You must adjust the speed of the annealing pan with the speed controller in order to achieve the desired annealing time. It has a digital readout showing the duty cycle from zero to 100 percent. The feed drum works the same way. They must be kept synchronized so that a case is fed in time for it to be waiting on the feed ramp when the opening notch comes around, but not so quickly that two cases are on the feed ramp at the same time. It is easy enough to tweak the feed drum speed controller occasionally, but I decided to automate the process by mounting a proximity sensor at the bottom of my feed ramp.

      This inductive proximity sensor is wired into the feed drum motor so that the motor runs when no case is on the feed ramp but the sensor turns off the power when a case is positioned close above the sensor in the waiting position. This part also comes from China and costs two or three bucks. I think it’s well worth incorporating it. Do not bother with a small mechanical micro switch. I tried it and quickly found that the cases are not heavy enough to actuate an ordinary switch.


      While I was shopping for my proximity switch, I stumbled across a cheap digital counter to increase the “bling” factor, but in fact, it is useful to count how many rounds I have just annealed. Beats counting them by hand anyway. It was easy enough to include it (and the associated counter zeroing switch) in the circuit once I had committed to the inductive proximity switch.

      Of course, there are many ways to deal with the miscellaneous mechanical items depending on your budget, skill level, and tool collection. If you are a construction worker, you might start with some 3/4″ OSB and a box of dry-wall screws; plenty of people have done that. Shooters have built all sorts of interesting variations including some ultra simple hand-fed models.

      I lean toward using nice components and I like to fabricate things that are light and strong. Consequently, I bought some hubs and spacers from an outfit called Servo City. Check it out here:

      Using a handful of these components, it was easy enough to build the machine using nothing more than some simple tools most homeowners have in their garage, along with a small fine-tooth handsaw and a small tabletop drill press. A table saw would be nice, but sold mine when I moved to Italy a few years ago. I made do with a jitter saw and a low angle block plane to true the edges of the plywood. There are many ways to skin a cat and the AR-15 forum thread will point out many options. Suit yourself. Each builder will have a different skill set, tool set, budget, and background.

      Based on my background as a boat builder and aircraft fabricator, I elected to make my box from 5mm cabinet grade birch plywood, available from Lowes or Home Depot in small sheets. This plywood is too thin to edge fasten, so after cutting out the parts I glued some 3/8″ square sticks along the edges. This is easy using ordinary yellow glue (or Krazy Glue) and some clothes pins as clamps.

      I improved on the original design by mounting every component on a removable front face. This approach is highly recommended even though most builders mount some components on the face and some parts on the other sides of the box. My method simplifies the wiring and makes assembly and fine-tuning much easier.

      Other than the removable face, the other five sides are just a simple box. The back has some vent holes near the top for cooling and a larger cut-out near the bottom so I can stuff the power cord and the propane hose inside for storage. The front face is attached with four screws that go into T nuts inside the corners of the box. This kind of box takes a little more time to make than one made from thick plywood or strand board, but it’s plenty strong, very light, and it looks a little nicer to my eye. It is held together mainly with glue. Note that the front face is slanted back at an angle so that the case won’t walk out of the rotating annealing pan.

      I bought some thin 2″ aluminum angle at my local hardware store that is only 1/16″ thick. Buy that if you can rather than use common angle stock at Lowes which is normally 1/8″ thick. The thin stuff is easier to cut, easier to bend, and doesn’t look so clunky.

      How about changing calibers? My machine is built for .223 Rem cases, but I also reload the fatter and shorter 6mm BR Norma cases. My feed drum notch is large enough to accept the larger diameter case; no worries there. However, the 6mm case is too short for the annealing pan. The solution is a simple shim that slips over the case stop rod. It literally takes seconds to switch from one caliber to the other. I made a rudimentary prototype but it worked so well, I simply continue to use it. It looks like this:


      I have also annealed .308 cases for friends, requiring only an adjustment to the torch holder. Others have dealt with changing calibers by making several annealing pans or adding a disk to the inside of the pan.

      So how do you know you are reaching the proper annealing time and temperature? Take some reject cases and paint the inside of the neck with 750F Tempilaq temperature indicating liquid. Adjust your annealing pan speed so that the case remains in the annealing pan for 3 or 4 seconds and then light the torch. I adjust my torch so that the tip of the blue pencil flame just touches the neck right just above the neck/shoulder junction. Once the case with the Tempilaq in the neck falls into the annealing pan, shine a strong light inside the neck. The Tempilaq should change colors from green to clear just as the case falls out of the pan. Fiddle with the timing until you get it set just right, making sure to let your cases cool off before testing them a second time. Once you have determined the perfect annealing time, load up the hopper with brass and go for it. No need to paint the necks of your cases once you find the correct annealing time; however, it is a good idea to check the calibration once in a while just to make sure. Be sure to perform another Tempilaq calibration test when you change calibers or if you use cases with a different neck thickness.

      I hope this article inspires a few people interested in making their own annealing machine. This “Skip Design” machine works as well as the very best units on the market at a fraction of the cost. Because it has an automatic feed feature and a generous hopper, it is superior to any of the much more expensive commercial machines that require hand feeding brass one case at a time. I would not trade my DIY unit for ANY machine currently on the market, regardless of the price.

      I will remind anyone thinking about building a machine that they should read the entire thread on the AR-15 forum. My article is simply an over view and does NOT contain everything you need to know.

      You might consider syndicating a machine with a friend. Perhaps one person can pay for the components, and another can do the building. Alternatively, if you know a person with a drill press and a table saw, maybe you could offer to fabricate the feed drum and box components if he will let you use his tools.

      With a good machine, like the Skip Design, annealing is so easy you won’t hesitate to do it every reloading cycle. Your neck tension will be more consistent and your brass will last so long you can stop counting how many times you’ve shot it. Keep shooting and reloading until the primer pockets wear out. That’s what I do.

      • This topic was modified 4 years, 6 months ago by Bob Walters.
    • #3874
      brett collins

      MR BOB that’s is a very interesting read. I may give it a try and thanks for posting. I will say that you wrote the book on it literally. LOL

    • #3876
      bryant hollinger

      I just build one of these machines although mine is not nearly as nice looking as yours! I still need to do a little tweaking on it but I think is gonna work nicely.

    • #3877
      Bob Walters

      Congratulations. If you have any feed problems or problems of some other kind, let me know and I’ll try to get you on the right path. These machines are simple, but there are a few tricks to getting to run reliably. I’ll be glad to help if I can.


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