Chapter 4 - Bolted Connections
Hole Size and Bolt Spacing
SCM J3.2 (pg 16.1-120) defines hole sizes and types. You need to review this section.
The vast majority of the time you will use standard holes, which are 1/16" larger in diameter than the bolts that they hold. However, in special circumstances you may want to use oversized or slotted holes. SCM Table J3.3 gives the dimensions that should be used for such holes.
Oversized and/or slotted holes are used when you either want to eliminate bearing as an option or do not want the connection to transfer force in one direction. They may also be used when construction tolerances may be an issue.
SCM J3.3 through SCM J3.5 list requirements for bolt spacing. You should review these sections.
Probably the most commonly used bolts fall in the 3/4" to 1" diameter range. The commonly used spacings for these bolts are 3" center-to-center of bolt and 1.1/2" from center of hole to plate/member edges. These spacings satisfy the requirements of the specification. Fabricator's have generally set up their equipment for these spacings and have extra labor associated with changing them to something else unless they have computer controlled drilling machines. It is good practice to maintain these spacings where possible.
If you decided to change to tighter spacings, you will need to show that they meet the requirements of SCM J3.3 through SCM J3.5.