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Chapter 6. The Gysin Device > Turntable and Base - Pg. 176

Gysin Device The arcana of thread nomenclature. What is a 5 / 16 -24 bolt anyway? In the case of SAE (Society of Automotive Engineers) bolts and machine screws, for diameters 1 / 4 " and over, the first part ( / 16 ) refers to the diameter of the bolt hole. The second part (24) refers to the number of threads per inch. Adding to the confusion, smaller shaft diameters are defined numerically (as in #4-40, # 10-32, yadda yadda) according to the pleasingly arcane formula: D(iameter)= N(umber) * 0.013" + 0.060. Engineers...waddayagonnado? The once-common numeric drill bit sizing Speaking of metric . . . don't ask me. Fractionally sized bits are fine for my personal purposes; even though I'm Canadian, and supposedly completely 5 Numerical Size 4 6 8 10 12 Diameter 0.11 0.14 0.16 0.19 0.21 Closest fractional drillbit that's actually gonna pass the shaft diameter 1 9 / 8 " / 64 " / 64 " / 64 " 11 13 7 / 32 "