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After careful mic measuring and a TPI gauge, I got the same thing last night but, like you, failed to find the bushing anywhere. I do not have a Lathe, however, I will be using a 3/4” - 16 compression fitting and boring out the center and tapping it to a 9/16” - 18. I paid $9.95 for a brand new NSS and I also refuse to pay the extra $50 - $75 for a ten cent bushing. If we could only find who made these. Thank you for an accurate answer to my question. BTW, I got penalized by doghead for starting different threads for a conversation on the switch and then another conversation about the bushing. Though initially not related questions, he merged them and gave me a point. Thank you!