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The Newbies Arena Are you new to knife making? Here is all the help you will need.

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  #16  
Old 02-19-2012, 01:11 PM
WBE WBE is offline
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Grain direction is determined and set when the bar is hot rolled longitudinally at the mill. Once set by the mill rollers, direction cannot be changed. The bar of course can be bent to a curve, but the grain will follow the bend, whether simply bent cold or forged. That is when forging becomes superior as the bar can be curved under heat with minimal stress, and increased strength over a casting, but as to the acual improvement of the steel quality in a mill rolled bar there is none what so ever from further forging. NOT my opinion, but hard fact. A cast hook would be risk involved because it was not originaly forged or rolled, and the grain has no specific direction. Forging a casting would not change the direction of the grain in a casting. It would still be haphazardly arranged. However, the grain size in a casting can be reduced with heat cycles.
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  #17  
Old 02-19-2012, 01:39 PM
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Ray Rogers Ray Rogers is offline
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Ed,

All good points but you may be getting more specific than I can handle. Maybe the casting temperatures are low as in a sintered product, maybe the metal isn't as high a quality. There are several kinds of industrial forging though and most of them aren't what we think of as forging. For instance, that hook is probably made with one smack between a set of dies. That would seem to me to point to the heat and the quality of the steel as the reason for using the process rather than any improvement from being massaged by striking since there wasn't any. We can agree that a forged hook is stronger than a cast one because - obviously - industrial engineers must think so because they specify that way - we just don't know the real and exact reasons this is so. It may be that the processes the steel went through prior to the actual forging might give us a clue (UPDATED: as WBE explained at the same time I wrote this). The metal bars are rolled and/or hammered into the proper size and shape prior to the actual forging into a hook but that takes us back to what Doug was saying about the ways steel is processed into bar stock.

We've got a couple of those alchemist you mentioned around here, maybe one will see this and clear this up for us. In any case, we know that forging a blade certainly is a way to produce a top quality knife. We also know that stock removal can do the same to all appearances. I know that some of the cutting competition knives are forged and others are stock removal and they both win from time to time. Thank goodness that we have two methods of producing high quality blades because knife makers are a kind of independent bunch of individualists and one size does not fit all .....


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Last edited by Ray Rogers; 02-19-2012 at 01:42 PM.
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  #18  
Old 02-19-2012, 05:02 PM
WBE WBE is offline
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There is certainly nothing wrong with forging a blade, if that's how one wants to shape it, but structurely, hammering adds nothing to the steel except stresses and uneven grain sizes, and possible carbon loss. The stresses and uneven grain size are easy corrected with heat cycling. Yes. One can reduce grain size by forging, but it will not be even sizing, and as soon as the steel is heated to an austenitization heat, the larger grains eat the smaller ones, and become even larger. To get the best possible even, and small grain size requires heat cycling. The hammer will not do it, but the heat will. The steel is heated to 75? to 100? beyond austentization with a short term soak. This grows the grain and the soak allows time for the grain to become evenly sized as the large absorb the small. After the soak, the steel needs a quick cool down, air cooling, to lock the grain size and carbon solution in place. From there another heat at the austentization temp, with a fast cool down. Then another heat at just non magnetic with a fast cooling, then 2 or 3 heats and cool downs a bit shy of non magnetic, and the grain will be about as small and evenly sized as possible. Then you can do the hardening process, using at least a short term soak at the critical heat. No amount of hammering can match that. Not even close!
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  #19  
Old 02-19-2012, 09:11 PM
Ed Tipton Ed Tipton is offline
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WBE...So, If I am understanding you correctly, then you are agreeing that forging does in fact alter the grain structure, but that the following addition of heat effectively nullifies any of the effects of the forging and takes over the development of the grain structure.
I admit that although I am able to get good consistant grain structure in my blades, I have never tried to give them a thermal cycling such as you have described, and so I have always attributed my success to the overall process which includes forging the blade. However, as I'm going through my forging, I am also subjecting the blade to several cycles of "co-lateral" thermal cycling (to use a military term as in co-lateral damage), so maybe the success that I have been having and giving the credit to forging, should rightfully have been given to the thermal cycling all along.
When you talk about heating the blade to 75-100 degrees above the austinization point and then rapidly cooling it in air, I assume you simply take it to "black heat" or do you take it all the way to ambient? Simply removing the blade from the fire and exposing it to the air for a couple of minutes will get it to a black heat. Is that fast enough....and is that cool enough? I can see where doing that thermal cycling would help with improving the grain size, but honestly, my grain size on my blades is approaching that of a broken porcelain dish right now....so I can't see where there is too much room for improvement....but having said that...I'm certainly willing to give it a try. Like I said, I consider myself to be an open minded person, and I'm not trying, nor have I ever tried to suggest that my way is the only way to do it, or even the best way to do it. It is just the way that has worked for me.

Last edited by Ed Tipton; 02-19-2012 at 09:37 PM.
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  #20  
Old 02-20-2012, 06:21 AM
WBE WBE is offline
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Your understanding is correct Ed. Your heats are resizing the grain after the hammer work. I should have said full austenitization A3, your critical quench heat as to the first step. The idea in this case is to grow the grain, let it soak long enough to become even in size, larger than wanted in the finished blade, then you can start reduceing the grain size with the lower heats and cool downs. You can quench at the just turned non magnetic step, and below that if you wish. I have just let the steel cool until I can handle it when I have done it. From what you are saying, whatever your exact process is, you are already heat cycling enough to work for you. Very well it would seem. If your grain is as fine as you say, I don't know as I would change anything. You might want to experiment with some scrap just to see if a separate extra process is worth the effort, but I am kind of doubting it. Grain in can be taken down so fine that it becomes difficult to get a full solution and hardness.
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  #21  
Old 02-20-2012, 08:44 AM
Ed Tipton Ed Tipton is offline
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WBE...Fair enough. Live and learn. I will give this a try on my next knife and see if there is any difference in the final product. I have to admit that it is embarrassing to think that I could have been mis-interpreting my own results after all this time....but your argument is compelling, and consistant with my own process....just different than how I was thinking about it.
I still enjoy the act of forging, but if this proves out, and I suspect that it will, I will probably put less of a premium on forging in the future, and even more emphasis on the heat treatment....which already gets a lot of attention.
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  #22  
Old 02-20-2012, 01:09 PM
WBE WBE is offline
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No need for embarassment at all. This is sort of an example for the root source of the edge packing myth. Smiths believed that they were acually tightening and refining the grain in the edge by the extra hammer work, but in reality it was the extra heats that they were giving to the edge grain that did the job. Good luck, and let us know what you find, but I am still guessing that your particular method in forging is not going to be over shadowed much, if any. It would seem that your way of working the steel you use is point on as is.
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  #23  
Old 05-09-2013, 03:45 PM
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miketheknife miketheknife is offline
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I know this is an old post but I think I have learned more in this one post than any one singular post to date. Thanks!
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