E-4. TIGHTENING METAL FASTENERS (continued).
Table E-3. Torque Ranges
MOST EFFECTIVE RANGE
E-5. FASTENER SIZE AND THREAD PATTERN.
Threaded fasteners are categorized according to diameter of the fastener shank. Thread styles are divided into broad
groups, the two most common being coarse (Unified Coarse-UNC) and fine (Unified Fine-UNF). These groups are
defined by the number of threads per inch on the bolt shanks. In addition, threads are categorized by thread class (Table
E-4), which is a measure of the degree between threads of bolt or screw (external threads) and threads of the attaching
nut or tapped hole (internal threads of the attaching nut or tapped hole) (internal threads). The most common thread class
for bolts and screws is Class 2.
Table E-4. Thread Classes and Description
NOTE: Unless followed with -LH (e.g., 314-10 UNC-2A-LH), threads are right-hand.