Used on Ariel 1937-58 square sump plate - Ariel part number 0520. Nuts are 1/4" whitworth BSW full nuts, 20tpi, bar turned with a single chamfer. Across flats (AF) = 0.524". Depth = 0.252". Four (4) new 1/4" x 5/8" Whitwroth BSW bolts with 4 x 1/4" BSW nuts and 4 x 1/4" washers.
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