I need to bolt some stuff together, and I found two really good references that (I hope) will save me from looking at every darn bolt and screw and nut at Home Depot, and then cursing when I get home with the wrong size.
First is a collection of printable PDF files showing every type of fastener on the planet, along with actual-size pictures. You probably want the one called "All Printable Tools and Charts".https://www.boltdepot.com/fastener-information/printable-tools/
And here is a table of bolt dimension data. The most valuable thing here is the "Minimum Clearance Hole Diameters" table, which tells you what size hole you need for what size bolt.https://mechanicalc.com/reference/fastener-size-tables