Typical Standards of Heavy Hex Bolts

Heavy hex bolts are treasured for their strength and durability. They are manufactured to certain specifications, making them distinctive from standard hex bolts. Although you may be able to find specific types of heavy hexes, there are certain standards found across the board.
Points and Shanks
Bolts typically have flat tips, although certain applications require a pointed tip. Lag bolts are used with lumber and the point is useful for installation. But heavy hex bolts are available in both blunted and pointed tips.
The shanks of hex bolts (both heavy and standard) are mostly straight. Fasteners can be manufactured within certain limitations – lengths of 12 inches and less can include a camber of no more than 0.006 inches per inch of shank. Bolts up to 24 inches long may have a camber of up to 0.008 inches per inch of shank.
Head Specifications
A heavy hex head is chamfered and the diameter of the round within that chamfer is equal to the maximum width across the flats, with minus 15 percent tolerance. Standards for the maximum and minimum across flats are dependent on the diameter of the bolt (also known as the nominal size).
For example, a 0.5-inch nominal size fastener should have a maximum of 0.875 inches across the flat and a minimum of 0.850 inches across the flat. A fastener with a 2-inch nominal size has a maximum of 3.125 inches across the flat and a minimum of 3.025 across the flat.
Body Diameter
A fin or swell may be included under the bolt head or die seam, within reasonable limits. It should not exceed the bolt diameter by 0.03 inches (for bolts with a 0.5-inch diameter), or 0.06 inches (for bolts from 0.75-inch to 1.25-inch in diameter), or 0.12 inches (for bolts from 2 to 3-inch in diameter).
In some cases a reduced diameter may be specified, although there are also limitations to that reduction. The diameter must not be reduced beyond the thread’s pitch diameter. These fasteners may also include a shoulder under the head in the full diameter, although this is at the discretion of the manufacturer.
Heavy hex bolts are made to certain specifications, making them distinct from standard hex bolts, hex cap screws and heavy hex screws.