blackleafforge

The physics of heat retention in worked stock?

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I have notice and heard smith make reference to the fact that working stock hard keeps the heat in. I find this mostly applicable when drawing down very small stock but I was wondering about what was going on. I assume that the impact of the hammer will generate a small about of heat through friction but I don't think that accounts for it. I thought it may have something to do with compression?

I also noticed this video that i assume is working off the same principle.

 

does anyone smarter than me know what exactly is going on? 

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Physics states that energy can not be created nor destroyed. only transferred

As you hit metal, the energy of the falling hammer into the stock that is not used for hammer rebound or moving metal, is converted to heat. simple,  but the formula to show how that gets divided is a bit more complex

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What happens when you compress air? It heats up, and can get hot enough to get a fire going.

Internal friction in the metal from moving produces heat.

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if it wasn't for the fact that he is giving himself lung cancer that would have been awesome.

i'll have to try that......

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I winced at the sight of the hot cut In the hardy hole, and even on the same side of the anvil as his hammer hand. But, he didn't loose a finger, so that's good. Yet.

                                                                                                                                      Littleblacksmith

                                                                                                                                        

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I notice that effect most when working under the power hammer, after all the energy involved is an order of magnitude (give or take) more then when working by hand.  Crush atoms past one another they get excited.  Electrical assist aside, on some smaller stuff for example upsetting rivet heads, if you hit hard enough fast enough you can get another second or two (2 or 3 blows) more out of a heat.  Makes the difference between needing another heat or finishing the part in one cycle.  Worth training up to get to that level.

On a side note, if you can hit the same spot 1 or 2 thousand times before lunch a hot cut in a hole 10 inches away is probably not a big deal.  I agree that it should be strongly cautioned against for beginners but of all the things that could kill or maim you in a blacksmith shop that one is pretty far down my list.  

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1 hour ago, Judson Yaggy said:

I notice that effect most when working under the power hammer,

I don't own a power hammer, but can relate when working on the far edge of the anvil. like when drawing out lets say a rr spike, if I work fast enough and draw it out how you should on the far edge of the anvil, than it will light up from a dull red to a bright yellow, and I can keep it that way so that I can go from 5/8 down to a little less than 3/8.

                                                                                                                                   Littleblacksmith

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6 hours ago, littleblacksmith said:

I don't own a power hammer, but can relate when working on the far edge of the anvil. like when drawing out lets say a rr spike, if I work fast enough and draw it out how you should on the far edge of the anvil, than it will light up from a dull red to a bright yellow, and I can keep it that way so that I can go from 5/8 down to a little less than 3/8.

                                                                                                                                   Littleblacksmith

Man, that's some feat LB! I've drawn out many a rail spike and hit as hard and as fast as I can at times, but I can't match that.

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7 hours ago, littleblacksmith said:

When working on the far edge of the anvil. like when drawing out lets say a rr spike, if I work fast enough and draw it out how you should on the far edge of the anvil, than it will light up from a dull red to a bright yellow, and I can keep it that way so that I can go from 5/8 down to a little less than 3/8.

Little blacksmith, Can you can please post a video of working the rr spike on the far edge of the anvil, than it will light up from a dull red to a bright yellow, and I can keep it that way so that I can go from 5/8 down to a little less than 3/8. 

Please mention IForgeIron in the video so we know it is the read deal.

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Ok, ill be out of town today, but can maybe do it then. funny thing is, is that I was planning on making a pair of flat jaw tongs out of some rr spikes, so this will fit right in. A bit clarification, just in case I wasn't clear enough. When I pull the spike out of the forge, it is a bright yellow, almost a forge welding heat. Then I begin drawing it out, and it obviously begins to cool. So, by then picking up my speed some, I can light it up. Now, I'll be honest, it may have been a bit of an exaggeration when I said from a dull red, to bright yellow. More like a red to a yellow. And when I said I can keep it that way, I meant that I can keep my pace, and in return, keeping the spike hot up to a point. Also, I'm not drawing out the entire spike in one heat down to 3/8", just a part of it.

                                                                                                                             Littleblacksmith

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I've seen a video of aJapanese Swordsmith light his forge by hammering an iron rod to light a piece of paper, traditional I believe.

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New students often comment on how I can work a piece much longer than they can between re-heats; they generally have not noticed that I'm hitting several times faster and much harder than they are---more "WHAM WHAM WHAM WHAM" to their "tap tap, stop and look at it"

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One of my biggest issues, is that after a few hammer blows, I want to look at the piece, ... and think about it some more.  :unsure:

Obviously, that's counterproductive, ... but it makes me happy, ... and that's why I came .....

 

.

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3 hours ago, SmoothBore said:

One of my biggest issues, is that after a few hammer blows, I want to look at the piece, ... and think about it some more.  :unsure:

Obviously, that's counterproductive, ... but it makes me happy, ... and that's why I came .....

 

.

I'm with you, I didn't get into this to make things hot by the sweat of my brow. Beat it for a while, take a look and think a while is my thing too, nor do I swing a very heavy hammer.

Frosty The Lucky.

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