DanCampbell Posted June 21, 2011 Share Posted June 21, 2011 Hello, I am working on a large knife and would like some advise. It's 5160 leaf spring, about 17 inches long. I'm not sure how thin the edge should be and I'm worried about buring the tip up. Also, how can I get a smooth finish with the hammer? is that where a flatter would help? Thank you Dan Quote Link to comment Share on other sites More sharing options...
CurlyGeorge Posted June 21, 2011 Share Posted June 21, 2011 Hi Dan and welcome to IFI. You didn't include your location, so I'm going to ask. You wouldn't be the Dan Campbell from central ILL that I know, would ya? :D Quote Link to comment Share on other sites More sharing options...
Don A Posted June 21, 2011 Share Posted June 21, 2011 The rule of thumb for a blade that size is for the edge to be about as thick as a nickel before heat treating... thick as a dime on smaller blades. This is after you have done all of your stock removal, so leave plenty there out of the forge. Two things will eliminate the hammer marks: 1. A grinder or file 2. Lots of practice The way it has worked for me is when starting out, "forge 'em thick and grind 'em thin". As you progress, your hammer control and technique will improve so that you can forge closer to shape and thus have less stock removal to deal with. I still come out of the forge with more meat on the blade than some I've seen, but I am more confident that I'll end up with what I wanted. In the past I have thought about a flatter or similar device, but I really don't think it would do what you want. Plus, it's a lot more important to just stay with it, practice, and learn good hammer control. My $.02, Don Quote Link to comment Share on other sites More sharing options...
DanCampbell Posted June 21, 2011 Author Share Posted June 21, 2011 Thanks for the tips, I will take it to the grinder. Quote Link to comment Share on other sites More sharing options...
DanCampbell Posted June 21, 2011 Author Share Posted June 21, 2011 Hi Curly, No, I'm near Warrenton, VA Nice to be here, seems like a good forum. Thanks for the welcome. Dan Hi Dan and welcome to FI. You didn't include your location, so I'm going to ask. You wouldn't be the Dan Campbell from central ILL that I know, would ya? Quote Link to comment Share on other sites More sharing options...
viking-sword Posted June 21, 2011 Share Posted June 21, 2011 I would also be inclined to ask about the type of heating method used. The reason is that by looking at the texture of this blade it looks like maybe a very oxygen rich fire was used and that also alot of low temp finish forging was done at the end. The excess oxygen will cause a great deal of pitting as well as scaling, at lower temps these pits and pock marks can be forged over not to be seen until you clean grind after forging and thus causing you to grind away more of the blade than intended to give a good clean surface. Low temp forging is okay but a majority of the benifits gained by it can also be gained by proper normalizing to reduce grain structure, something very necessary for good heat treatment any way. By forging in a reduced oxygen atmoshere and good finish forging on a good clean anvil face you can forge much closer to dimensions. There is also another way to forge for scale free finish that some smith employ nowadays, and that is to to wet forge, and what this is, is forging on a wet anvil face and periodically dunking yor hammer face in water just before forging. The water turns to steam as the hot blade comes in contact and litterally blows the scale off as you forge leaving a cleaner blade surface, just something to consider looking into. Wes Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted June 21, 2011 Share Posted June 21, 2011 Also straighten that blade so the edge is all at the same place. Doesn't matter as much if the back is a little wonky but you have to remove the high spots to make the edge straight and that wastes width! So heat it up nice and red and set it edge down on a flat plate of steel and tap the back until all the edge is in contact for the straight part of the edge. Quote Link to comment Share on other sites More sharing options...
CurlyGeorge Posted June 21, 2011 Share Posted June 21, 2011 Hey Dan. Thanks for the response. The reason that I asked is that the man that I know up here also makes blades, although by the stock removal method. I thought that maybe he started forgeing. :) Quote Link to comment Share on other sites More sharing options...
DanCampbell Posted June 22, 2011 Author Share Posted June 22, 2011 Hi, I am using a charcoal forge, am am forging the heavy work at a yellow color and then light taps at just above non-magnetic. As far as the edge not being straight I was going for a bit of recurve (Kukri / Parang) theme but that is open for change. Thank you all for the help, this is my very first one. Dan Quote Link to comment Share on other sites More sharing options...
Altusjg Posted July 1, 2011 Share Posted July 1, 2011 I've found that keeping the steel good and clean while forging will also prevent as much pitting. I wire brush the steel coming out and going in the forge. Just my 2 cents. Quote Link to comment Share on other sites More sharing options...
Steve Sells Posted July 1, 2011 Share Posted July 1, 2011 Hi, I am using a charcoal forge, am am forging the heavy work at a yellow color and then light taps at just above non-magnetic. Way too hot for carbon steels. that is about welding temp. orange to red is plenty for non and low alloy steels Quote Link to comment Share on other sites More sharing options...
MattBower Posted July 1, 2011 Share Posted July 1, 2011 Hi Dan. I live in Prince William County, a bit north of Quantico. I don't get out your way that often, but shoot me a PM and maybe we can get together and forge sometime. I have used a flatter on wide, flat blades, as a final step before going to the grinder. I found it somewhat helpful, but it's no miracle cure. As others have already suggested, eliminating those big pockmarks is mostly a matter of good forging practice -- heating in a reducing atmosphere, keeping the anvil clean (and relatively free of dings and blemishes), and removing scale frequently while forging (whether it's by wire brushing or wet forging). Big dings from the hammer can also make the surface look rough, and the only solution for those is hammer control, which is a matter of practice. I have to disagree somewhat with Steve about high heat being completely inappropriate for carbon steels. It depends on your definition of high heat. If you're seeing sparks you've blown it (at least as far as blade steels go). But if you look at references like the Heat Treater's Guide, the recommended forging range for simple carbon steels is from around 2100 F down to 1500. I don't go quite as high as 2100, at least not intentionally, because I do most of my forging with coal and it's easy to burn steel, so I try to leave myself a bit of a buffer. (Industry is also normally working with heavy hammers and presses, so their steel gets shaped much faster and the total time at high temps is lower than what you get with hand forging.) But for heavy reduction -- drawing out tangs, making integral bolster blades from thick cross-sections, etc. -- I generally start at what I'd call a low yellow heat, with a fairly large hammer. I lower the forging temps and the hammer size as I get closer to final shape and start to develop easily burnt points and thin areas on the blade. Higher heat causes a lot more scaling, so that's another reason to lower the temps as you approach finished shape. I try to stick to the advice not to forge below around 1500 F, although like many smiths I sometimes can't resist a few extra whacks. But there's nothing to be gained by low temperature (sub-1500 or so) forging that you can't do better with proper heat treatment, and with less risk to the blade. Here's some good advice on this subject: http://www.cashenblades.com/forging.html Quote Link to comment Share on other sites More sharing options...
overmodulated Posted July 2, 2011 Share Posted July 2, 2011 Way too hot for carbon steels. that is about welding temp. orange to red is plenty for non and low alloy steels Steve: what is the drawback of being too hot with high-carbon steel? (other than the obvious risk of melting the surface a little, which might be fine before taking it to the grinder?) Thanks Quote Link to comment Share on other sites More sharing options...
MattBower Posted July 2, 2011 Share Posted July 2, 2011 Impurities and potentially oxides segregate along the grain boundaries, which embrittles the steel. It's very difficult or impossible to reverse this. Quote Link to comment Share on other sites More sharing options...
overmodulated Posted July 2, 2011 Share Posted July 2, 2011 Impurities and potentially oxides segregate along the grain boundaries, which embrittles the steel. It's very difficult or impossible to reverse this. potential? what if the oxides don't eat my steel? Quote Link to comment Share on other sites More sharing options...
Steve Sells Posted July 2, 2011 Share Posted July 2, 2011 Steve: what is the drawback of being too hot with high-carbon steel? (other than the obvious risk of melting the surface a little, which might be fine before taking it to the grinder?) Thanks We all have our ways to do things, however I stand behind my statement of welding temps are not good for general forging of higher carbon steels because of increased grain growth, scaling and risk of burning is an issue. All these are things a new smith should not have to worry about with all the other things he needs to learn. About the oxides, if they are their already? how can you prevent it, if the Oxygen has joined with the steel... Quote Link to comment Share on other sites More sharing options...
MattBower Posted July 2, 2011 Share Posted July 2, 2011 Grain growth can be fixed. It's fine to suggest that a new smith not forge at such high temps, but that's not the same as saying that yellow is categorically "way too hot" for forging blade steels. It isn't. Welding temperature of course varies by steel, but I'm talking several hundred degrees below that. With respect to the oxides, I'm not talking about superficial scale, which we all deal with. I'm talking about oxides penetrating the grain boundaries of the steel. This can happen if (1) you get the steel to solidus temperature (so that the grain boundaries start to liquefy), (2) in an oxidizing atmosphere. Unless those two things happen, there won't be any oxides along the grain boundaries. If those two things do happen, you've blown it. Trash that piece and start over. Quote Link to comment Share on other sites More sharing options...
Steve Sells Posted July 2, 2011 Share Posted July 2, 2011 Grain growth can be fixed. It's fine to suggest that a new smith not forge at such high temps, but that's not the same as saying that yellow is categorically "way too hot" for forging blade steels. It isn't. Welding temperature of course varies by steel, but I'm talking several hundred degrees below that. dont forget that once again we have the issue of what you think is yellow vs what I call yellow heat. JPH talks a lot about that problem, an example is his description of how he welds at a cherry red heat, I cant weld at what I call that color. either way, we do seem to agree he was too hot and scrap that blade. Quote Link to comment Share on other sites More sharing options...
MattBower Posted July 2, 2011 Share Posted July 2, 2011 I might go ahead and grind and HT it, and see what happens. I woulfdn't sell it, for sure. A little caution is warranted. Color is definitely subjective. 1500 looks solid orange to me. Some call that a low red. Ambient light makes a huge difference. Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted July 5, 2011 Share Posted July 5, 2011 Note that most information on heat treating is given for items at least 1" in thickness---what works for a chunk of machinery can be pretty bad on something less than 1/8" thick! (I too have the ASM Handbook(s).) General issues are: Scaling, Decarburization and Grain Growth of those only Grain Growth is usually correctable *afterwards* Re Colours: remember that most old smithing books are referring to red-orange *pie* cherries when saying "cherry red" and not the modern Bing Cherry which are a red-black. I've met many a modern smith who has never seen old fashioned pie cherries on the tree---they get dyed red in the can! Quote Link to comment Share on other sites More sharing options...
MattBower Posted July 5, 2011 Share Posted July 5, 2011 Note that most information on heat treating is given for items at least 1" in thickness---what works for a chunk of machinery can be pretty bad on something less than 1/8" thick! (I too have the ASM Handbook(s).) General issues are: Scaling, Decarburization and Grain Growth of those only Grain Growth is usually correctable *afterwards* Re Colours: remember that most old smithing books are referring to red-orange *pie* cherries when saying "cherry red" and not the modern Bing Cherry which are a red-black. I've met many a modern smith who has never seen old fashioned pie cherries on the tree---they get dyed red in the can! All true, although on blades the first two will usually be dealt with by finish stock removal, assuming you follow the old, "forge thick, grind thin" maxim. Unless you're spending a great deal of time at welding temperatures, the decarb layer isn't likely to be very thick at all. But as I said, I forge at lower temperatures as thin areas begin to develop. Quote Link to comment Share on other sites More sharing options...
basher Posted July 11, 2011 Share Posted July 11, 2011 Note that most information on heat treating is given for items at least 1" in thickness---what works for a chunk of machinery can be pretty bad on something less than 1/8" thick! (I too have the ASM Handbook(s).) General issues are: Scaling, Decarburization and Grain Growth of those only Grain Growth is usually correctable *afterwards* Re Colours: remember that most old smithing books are referring to red-orange *pie* cherries when saying "cherry red" and not the modern Bing Cherry which are a red-black. I've met many a modern smith who has never seen old fashioned pie cherries on the tree---they get dyed red in the can! well there you go , I had always wondered about that as a description..... Quote Link to comment Share on other sites More sharing options...
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