KC-130J Posted February 25, 2019 Share Posted February 25, 2019 Greetings, So I am quite inexperienced to bladesmithing and have some questions that I hope the veterans can help me with. I have attached pictures of my 2nd and 3rd attempt at knifes and then both of them "finished". My 2nd attempt was just an attempt at a blade shape that I don't know what could be classified as. My 3rd attempt was an attempt at a paring knife. Both are made of aircraft grade bolts that are shown in the first picture. I stripped the cadmium plating with acid before forging. I've heat treated and tempered them and even did a test piece. The test piece was very hard to break (6+ hits on a small section sticking out of the vice with my forging hammer, with no bending ) and the grain structure looked good to my inexperienced eyes. I have the government specs for what the bolts should be made of. There are 5 different compositions that the contract requires and I'm starting to get confused because they seem to be pretty different types of steel. I looked the part number (5306-00-619- 5811) up on www.iso-group.com and it listed that the bolts can be made from 4140, E4340, 6150, 8735, or 8740. I've looked up all those steels on www.steelforge.com to look up their characteristics and I'm still wondering if it's worth my time. Finally, I've tried to search each composition with the "comp # and knife" to find opinions on the possible types of steel and still don't know if I should continue forging them. My overall questions are: With the range of steel that the bolt can be made of, is it worth my time? My (small) blades are holding and edge and are tough, is that a fluke? P.S. feel free to critique my early work so I can improve myself. --Max Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted February 25, 2019 Share Posted February 25, 2019 So your testing indicated that your material was Tough rather than Hard. Knives usually go with Hard over Toughness as hardness is correlated with edge holding. All those alloys listed are medium carbon alloys---the last two digits indicate carbon content in points with 100 points equalling 1% carbon (hence what folks like to use bearings that are made from 52100 a 5 digit number as it has 100 points C.) If I had to make a blade from one of those alloys I'd go with the 6150. Every alloy is good for some uses, ok for some uses, and bad to very bad for some uses. I would NOT expect an alloy that was great for aircraft bolts to be good for knives as they have very different requirements. Good think you checked out the steel before spending a lot of time trying to make a good blade from it! Quote Link to comment Share on other sites More sharing options...
JHCC Posted February 25, 2019 Share Posted February 25, 2019 The brass pin closest to the blade on the straight-edged knife is a crack waiting to happen. Especially with coarse-grained woods like oak, you want enough wood on either side of the hole that it's not going to split itself apart. Quote Link to comment Share on other sites More sharing options...
Irondragon Forge ClayWorks Posted February 25, 2019 Share Posted February 25, 2019 Been there done that, both knives have the pins too close to the front of the scales. Quote Link to comment Share on other sites More sharing options...
KC-130J Posted February 26, 2019 Author Share Posted February 26, 2019 Thank you guys for the input. This is why I did this post, input to better myself. I'm starting to understand the numbers now. From even further research, the requirement for these bolts list the carbon content that can vary from 0.32% up to 0.53%. Knowing that the bolts could be made from anything in between make me want to get some known alloy. I still have a bunch of these bolts laying around that I'd like to continue to practice on. Should I practice with known alloys or are these "maybe" alloys possibly feasible for lightly used blades? Quote Link to comment Share on other sites More sharing options...
Latticino Posted February 26, 2019 Share Posted February 26, 2019 You can use anything for practice you want. Even practicing grinding with old wood yardsticks can be helpful. However you will get better experience learning knife forging using steel with at least 60 points of carbon and some additional alloying elements (like 5160 leaf spring), or even better some 1084. Higher carbon content steel behaves differently under the hammer and in the forge. And you can start to learn something about proper heat treatment as well. I would save your bolts for forging chasing tools and drifts, or just as fastners (you will always need some). BTW, nice job forging out that second blade from a small bolt like that. Redistribution of mass is what forging is all about, and that level of change is far from easy for a beginner. Quote Link to comment Share on other sites More sharing options...
MilwaukeeJon Posted February 26, 2019 Share Posted February 26, 2019 Do the bolts spark differently from one another on a grinder? Also, be very careful with that break test. That piece can fly off like a bullet in any direction. Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted February 26, 2019 Share Posted February 26, 2019 The problem with practicing with non-knife grade steels is that they work differently than knife grade steels: different forging ranges, different stiffness under the hammer, different "gotchas" with contact quenching, burning, etc. So you can practice in some really bad habits. Quote Link to comment Share on other sites More sharing options...
Steve Sells Posted February 26, 2019 Share Posted February 26, 2019 best way to practice with mild steel is to just make the tools you need, tongs, coal rake, punches drifts... Quote Link to comment Share on other sites More sharing options...
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