Wednesday, March 14, 2007

This is aimed mainly at Bill's comments on the heat treating posting. I think the general readers may find our experiences of interest. If you have not read his comment to the last post - you certainly should then come back here...


I got a lot of the theory behind heat treating that I know from a lecture by Philip Baldwin of the New England Guild of Bladesmiths - years back. Phil is certainly one of the top layered steel makers in North America, if not the world. He also not only understands the science, he was able to reduce it down to practical advice.
The ideal quenching oil would have an extremely high vapor point. That would allow it to pull heat away without bubbles, which leave voids that result in uneven cooling. The historically preferred medium was actually whale oil. Modern quenching oils are basically synthetic whale oil (!) He said that they had found bacon fat rendered to grease a good subsitute, but also mentioned the stench. he also recommended a fine cooking oil like cannolla or olive oil.
I personally have had good results with new 10 W 30 motor oil. Thats both for 1045 spring steel for swords and long blade tools, inset edges on axes and 1095 on short knives. I usually also use this oil on the layered steels. I personally have not used the 5% salt. I do know that Lloyd Johnson has mentioned using molten lead for certain tasks (never tried that one either).
I would stress that the function of the tool, the metal chosen and the quenching medium have all got to work together in balance to create the desired effect in the final object.

Bill said:
"When I get swords made for me, a professional heat treating company in Montreal will harden them, then dip them in salt to drag them down to Rockwell 50 to 51. They usually come back to me all warped and twisted. One in ten is un-recoverable. I had to learn how to straighten out a hardened and tempered tool."

Geezz - get a new heat treating service! They are obviously doing something very wrong. If you have correctly annealed the blades (or are paying them to do this) there should be NO warps. I'd almost be certain they are quenching the blades by laying them flat down into the liquid. Swords should ALWAYS be quenched point first. This takes a special container to be made up. I use a piece of 6" wide ABS plastic pipe with a sheet metal liner. It holds about 3 gallons of oil, and is a pain to hold and empty. I have never had any problems with warping (and certainly never twisting) on any of my forged blades. (We will leave aside the pattern welded blade that shattered - that was an entirely different problem!)


No comments:


February 15 - May 15, 2012 : Supported by a Crafts Projects - Creation and Development Grant

COPYRIGHT NOTICE - All posted text and images @ Darrell Markewitz.
No duplication, in whole or in part, is permitted without the author's expressed written permission.
For a detailed copyright statement : go HERE