"Serious" Iaidoka nearly always use Zinc-alloy and only use steel variants if they are shinken.
Interesting comment, Mat. I wonder what your definition is of "serious." Of the five iaidoka who had zinc-alloy blades break, all but one are yudansha, & Sensei is kodansha. Like my wife & I - also yudansha - they have all switched to steel iaito.
Are you of high enough rank or possibly heading up your own ryuha that you can make a blanket statement like this for all iaidoka? As you have chosen, by your own words, to "hit a steel joist" with your blade, I rather doubt that this is the case....
Ken
Ken Goldstein
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Judo Kodansha/MJER Iaido Kodansha/Jodo Oku-iri
Fencing Master/NRA Instructor
"A positive attitude may not solve all your problems, but it'll annoy enough people to be worth the effort."