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Rifles, Reloading, Optics, Equipment
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Melonite Process
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<blockquote data-quote="Trickymissfit" data-source="post: 956620" data-attributes="member: 25383"><p>keep in mind that virtually all modern carbon steel actions are built off a 4*** series steel. They can be ordered in as a pretreat steel that will usually Rockwell at 28rc -32rc. Now one can take that piece of pretreat steel and hard turn it (a machine process normally associated with machining something that is hard). This same piece of steel can then be nitrided in one of three forms of the nitride process. I used mostly the gas type and the plasma types, and have not used a salt bath in 20 years. But the salt bath works well. Most of the time I did .025" case or a .035" deep. Takes 29 hours for a .035" case as I remember. There are high speed processes, but the slower it's done the better quality and uniformity. Steel in a pretreat form is ready right out of the box. Have used 4150 (literally tons of it), 4140, 4340, 4350, and a small lot of 4360. Results were similar in each case. Now with a soft piece of 4*** series steel things change a bit. But still is easy to do. You can have the steel blank cut with extra stock here and there, and left alone in critically finished areas. Then send out and have it carburized and hardened. (also does well with 8620) Then recut the blank a second time. This makes the areas that need to be hardened stay hard while the rest is machined away (like a bolt seating area). The hardest you'll ever see out of a 4*** steel is 47rc-50rc without the nitride process. Each method has it's own set of advantages, as well as it's own set of demons. Trust me the furnace operator and piece of equipment has everything to do with the process. I had access to about a hundred nitride setups ranging in size from three feet in diameter to a hundred feet long.</p><p> </p><p>Now cutting a piece of nitrided hardened piece of steel is not all that big a deal contrary to popular belief. You need a lathe with a heavyduty carriage and bearing pack in the headstock. Kinda hard on a Bridgeport mill, but have done it. Mostly depends on how deep the case is. A .015" case is not much to worry about, but a .035" one shows it's ugly head. I used carbide inserts that were made for hard turning very hard steels (Valenite), and were coated. Still a diamond insert was better, and ceramic makes short work of it. End mills are another story, and carbide is a must. Drilling and tapping holes is easy, and you simply break thru the case with a carbide center drill. After that everything is soft. Forget reaming processes unless you find away to remove the hard metal case. Recrowning a barrel should be pretty easy with the right inserts.</p><p>gary</p></blockquote><p></p>
[QUOTE="Trickymissfit, post: 956620, member: 25383"] keep in mind that virtually all modern carbon steel actions are built off a 4*** series steel. They can be ordered in as a pretreat steel that will usually Rockwell at 28rc -32rc. Now one can take that piece of pretreat steel and hard turn it (a machine process normally associated with machining something that is hard). This same piece of steel can then be nitrided in one of three forms of the nitride process. I used mostly the gas type and the plasma types, and have not used a salt bath in 20 years. But the salt bath works well. Most of the time I did .025" case or a .035" deep. Takes 29 hours for a .035" case as I remember. There are high speed processes, but the slower it's done the better quality and uniformity. Steel in a pretreat form is ready right out of the box. Have used 4150 (literally tons of it), 4140, 4340, 4350, and a small lot of 4360. Results were similar in each case. Now with a soft piece of 4*** series steel things change a bit. But still is easy to do. You can have the steel blank cut with extra stock here and there, and left alone in critically finished areas. Then send out and have it carburized and hardened. (also does well with 8620) Then recut the blank a second time. This makes the areas that need to be hardened stay hard while the rest is machined away (like a bolt seating area). The hardest you'll ever see out of a 4*** steel is 47rc-50rc without the nitride process. Each method has it's own set of advantages, as well as it's own set of demons. Trust me the furnace operator and piece of equipment has everything to do with the process. I had access to about a hundred nitride setups ranging in size from three feet in diameter to a hundred feet long. Now cutting a piece of nitrided hardened piece of steel is not all that big a deal contrary to popular belief. You need a lathe with a heavyduty carriage and bearing pack in the headstock. Kinda hard on a Bridgeport mill, but have done it. Mostly depends on how deep the case is. A .015" case is not much to worry about, but a .035" one shows it's ugly head. I used carbide inserts that were made for hard turning very hard steels (Valenite), and were coated. Still a diamond insert was better, and ceramic makes short work of it. End mills are another story, and carbide is a must. Drilling and tapping holes is easy, and you simply break thru the case with a carbide center drill. After that everything is soft. Forget reaming processes unless you find away to remove the hard metal case. Recrowning a barrel should be pretty easy with the right inserts. gary [/QUOTE]
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