Size standards for tube and pipe evolved over time across numerous industries. The outside diameter (OD) and inside diameter (ID) of a pipe can vary greatly based on “schedule” or wall thickness. Certain schedules became preeminent based on their widespread use Sometimes pipe dimension variables can be confusing when trying to determine the size of equipment to specify for a particular machining operation. In addition, the size reference for tubing is usually an actual dimension whereas standard pipe sizes may not reflect the measured dimension.
For example, a 4” tube measures 4.0 inches in diameter. A 4” pipe OD measures 4.50 inches. The schedule can greatly affect the bore diameter within a given pipe size. A 4” (Sched 5S) pipe has a 4.334” bore whereas a 4” (Sched XX) pipe has a 3.152” bore.
This is why you must consider the absolute mounting range of a machine as the schedule determines the minimum bore that a mandrel can fit into for ID mounted machines, and actual pipe circumference can affect mounting for OD mounted machines.
Refer to our free Pipe Schedules and Dimensions Wall Chart or handy Pocket Pipe Charts for accurate pipe sizes, or call anytime for help in determining the best tools for your job.