Write Up of the March 29, 2014 CDBA Meeting by Jack ConnellApr 21, 2014
This meeting had another good turnout which included members, guests, and greenhorns.
Gil’s demo on the various aspects and steps towards hardening and tempering high carbon or tool steel (having at least 0.2% of carbon) was clear and informative. Gil initially demonstrated how steel taken up to the point of being non-magnetic (1500 degrees +-, or dark yellow) when quenched too quickly is as brittle as a candy cane and when lightly tapped will snap in two. To move from this brittle state to a useful one, the steel needs to be "Tempered".
Tempering relaxes the steel and changes the interior crystal size from large, brittle crystals to smaller more relaxed and stable ones. As Gil demonstrated, this tempering is done by taking the above heated steel and quenching the first inch or so (pre-taper the edge, assuming that you are making a chisel) into the water quench (or could be oil, depending on the ultimate use and/or steel type), swirl it around a bit and make sure you have sufficiently cooled this tip. Then withdraw the steel from the quench and quickly, while there is still most of the heat remaining in the shaft, with a file or angle grinder, polish one side of the cooled tip. This polished section is where you will see the various colors slowly moving towards the cooled tip edge, the first color to show and move down to the edge is light straw followed by the other colors. Each color will represent a degree of hardening. Once the wanted color/hardness is at or very close to the cutting edge, immediately quench the whole piece of steel again to stop/arrest the color. Gil used a propane torch to get these colors. This is a simpler, cleaner, easier and more predictable way to control the heat transfer and helps insure that you can see and can stop the color where and when you want it. The color chart and scale (the oxidation color spectrum) that Gil showed is a real good tool to use to compare the color of your work piece edge and thus the needed hardness. Generally, the rule of thumb is that “straw” color will cut stone; “Bronze” will cut steel; “peacock” will cut wood; and the color “purple” will give the high carbon steel a “springiness” and finally, “blue” will keep the steel relatively soft. Keep in mind that there are other methods of tempering, but all have the essential ingredients noted by Gil. We again thank Gil for sharing his knowledge and look forward to him demonstrating again at another monthly meeting in the near future.
Speaking of which, here is an updated monthly meeting schedule. However, as you can see, we still have many gaps and need someone to step forward to demonstrate (can be on anything related to steel – this can mean even steel design / architecture demonstrated on paper) for the months noted. Any volunteers please speak up!
April 27: lee Harvey on bells
May 18; Noah Khoury on Dutch hinges
June 29: ??
July 27: Travis Edginton: Forging an axe head.
August 24: Mark Feldman on casting
September 28: Mike McCarthy at Mike Cataldo's forge: Finishing techniques
October 26: Peter Schmidt on forging a very unique wine glass holder which goes on a wine bottle. This is Pete's own design.
November 23 (or 30th): ??
December 28: ??
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