I am putting two gusset plates to hold truss supports on my homebrew 30m Moxon. I'm using 1/4'' X 20 bolts. It's been 40 yr.s since I worked in a machine shop. Don't have the proper hole size chart for taps anymore. I assume the hole size to be threaded 1/4 x 20 is less than 3/16''. Anyone have a chart showing the proper size.TNX K9IL