Friday, July 15, 2011

Swarf






As a kid my contacts with metal working were rather skimpy. I flattened tin cans and nailed them to carts and tree houses and we covered a knothole in a chicken house with a tin can lid securely screwed to keep out mice and snakes.



Bent nails were straightened using a claw hammer and a rock anvil. I cut some steel with a hack saw, did some filing and a little chisel work. All my was done cold and it wasn’t much fun. Wood, especially from orange crates, was the preferred material for building something. Any early tool using experience probably eventually pays off even with the price of a few smashed finger nails, blood blisters and water blisters.

It was pretty neat for me to watch someone with a drill press use a twist bit to go through steel cutting out the curly strips and chips. I never dreamed that amusing stuff had an actual specific name - swarf.

From http://www.merriam-webster.com/dictionary/swarf - Definition: material (as metallic particles and abrasive fragments) removed by a cutting or grinding tool. Origin: probably from Middle English swerf, from Old English geswearf, gesweorf; akin to Old English sweorfan to file away. First Known Use: 1565
For more detail see: http://en.wikipedia.org/wiki/Swarf

When I’m cleaning up the swarf today around the drill presses, band saws and cold saw I find a small rare earth magnet on a handle pretty handy. That’s what got me thinking about those childhood experiences with iron.

The brick street in front of our house had concrete curbs. The street sloped to the south where at the end of the next block rain water was captured in a culvert which ran under the Katy Railroad tracks. When we got a good rain sand would wash down and deposit at intervals in little sand bars near the curb. When dry the sand was a good place to mine for some small treasure, perhaps a coin. I found a bullet once. Besides something to dig with the favorite tool was a magnet. It was fascinating to see that quite a bit of the deposited grit was magnetic. It’s not really surprising though remembering that iron is the fourth most abundant element in the earth’s crust.

I don’t recall that we found anything useful to do with the magnetic “dirt” but sometimes it was associated with little pea-size pieces of soft red stone, similar to red chalk. It was the non-magnetic iron oxide hematite, Fe2O3. Those were great for painting indian war paint stripes on our faces and arms. I suppose the black magnetic stuff was magnetite, Fe3O4.

It was a long journey from my early iron-age to today. In a small way that story recapitulates a larger history. Iron ore isn’t worth much without heat. Learning how to use heat to manipulate the element is the key to obtaining useful metal and to eventually forming metal products.

My woodworking abilities improved a lot from the orange crate period, but I sure wish I can been drawn into the iron working sooner. Today most of my work is done hot and it’s a lot of fun.

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