Size Dsignations

The size of rigid tubing is determined by its outside diameter in increments of 1/16 inch.Therefore,a-4 tubing is 4/16 or 1/4 inch in diameter.A tube diameter is typically printed on all rigid tubing.

Another important size designation is the wall thickness,since this determines a tube's strength.Like the outside diameter,wall thickness is generally printed on the tube in thousandths of an inch.

One dimension that is not printed on rigid tubing is the inside diameter.However,since the outside diameter and wall thickness are indicated,the inside diameter is determined by subtracting twice the wall thickness from the outside diameter.For example,if you have a piece of-8 tubing with a wall thickness of 0.072 inches,you know the inside diameter is 0.356 inches.

Inside diameter = Outside diameter - (2 x Thickness)

0.5 Inch - (2 x 0.072 Inch) = (2 x thickness)

Table 1 : Dash number / OD relationship

Fluid Line Size (Dash Number) Outside Diameter (OD) in inch

-4 1/43

-6 3/8

-8 1/2

-10 5/8

-12 3/4

-14 1