Well, Teletype is kind of weird in using 5-40 and 6-40 where most folks would use 6-32. 
And using 1/4-32 instead of 1/4-28. 
But who in the world decided on 1/4-27 for lampshade finials? Where did *that* come from?
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Nick England K4NYW
www.navy-radio.com