Does the length of a cap screw include the head? How many threads per inch for the fine version of a 1/4″ bolt? Bolt Depot has all of this information neatly collected in one place. I highly recommend bookmarking them. They have tap and drill charts, identification charts, thread tables, and all sorts of information for correctly identifying, specifying, and measuring bolts and screws. Their printable charts are great for fast identification and reference.