Dimensions of SAE Port Pads
FLUID POWER - Design Data Sheet 59
Information on SAE port pads was obtained primarily from SAE
J518 specification. For additional dimensions, that source may be
1. Many hydraulic components, particularly those of
large size and those operating at high pressure, are manufactured
with SAE 4-bolt port pads with rectangular bolt hole mounting
pattern. Advantages of this type of fluid connection are that it
can operate at high pressure with no leakage; it can be
disconnected and re-connected many times without developing a leak;
it forms a union joint for easy disconnection; the mating flange
can be attached with tools much smaller than required for pipe
threads, straight threads, or a swivel fitting; and the sealing
element, an O-ring, can easily be replaced if damaged, or changed
to another seal compound. Originally, the 4-bolt pad was designed
for connections of 1-inch size and larger, although it is available
in smaller sizes.
There are two series of bolt patterns. One (referred to usually
as the 3,000 PSI series) is for lower pressures, in the range of
500 to 5,000 PSI depending on the size. The other (referred to
usually as the high pressure or the 6,000 PSI series) has larger
bolts, longer and more widely spaced. It is rated for up to 6,000
PSI in all sizes. Mounting bolt pattern is different for these two
series. Connecting flanges designed for one series will not fit the
bolt pattern for the other series. There are several types of
connecting flanges which may be used to connect into these port
Figure 1. Many hydraulic components
port pads with standard SAE rectangular bolt spacing.
Pipe Connections to an SAE Port Pad
2. Solid flanges are used for connecting pipe or
tubing into an SAE port pad. These flanges are available either
with dryseal (NPTF) threads for pipe, or with a plain round bore
for welding to pipe or tubing. In all cases, the hole diameter
through the flange and through the pad is the same as the rated
size of the port.
The O-ring seal is located in a circular groove on the inside
surface of the solid flange and is pressed against the flat surface
of the port pad as the bolts are tightened.
A mounting kit for a solid flange consists of four high tensile
cap screws, four lockwashers, and one O-ring.
Figure 2. Typical solid flange with
socket for connecting pipe to an SAE port pad.
Hose Connections to an SAE Port Pad
3. These port pads are especially desirable for
connecting hose to avoid any twist in the hose during assembly.
Hoses should have an SAE flange end either straight-thru or
angle type. The O-ring is contained in a circular groove on the end
surface of the flange. The flange is mounted to the port pad with
two half flanges (called a split flange). Hose flange ends are
available in straight-thru type or with angles of 22½, 30, 45, 60,
67½, or 90 degrees. Since high pressure hose will not bend in a
sharp radius, it is important to carefully plan lengths and angles
when ordering hose.
The mounting kit for each hose end consists of four high tensile
cap screws, four lockwashers, two split flange halves, and one
O-ring. Split flange mounting kits can usually be purchased from
the hose supplier when ordering hose.
Figure 3. Hoses may be ordered with an
SAE flange fitting. They can be bolted to the port pad with a split
Notes on SAE Flanges
a. Solid flanges in the high
pressure series are not usually offered with pipe thread
connections; only with weld sockets.
b. One disadvantage of SAE pads,
especially with split flanges is the possibility of human error in
attachment. When mounting a flange to a port pad, the bolts should
be finger tightened to be sure the flange is going on straight.
Then all four screws should be tightened to the same torque, going
in rotation and tightening each one a little at a time.
c. SAE flange unions for joining two
pieces of pipe or tubing are made to the same bolt spacing as shown
in the tables. They use one standard solid flange with clearance
holes for mounting bolts, and with contained D-ring seal This is
mated to a "companion flange" of similar dimensions which has
threaded bolt holes but without the O-ring seal.
d. Some hydraulic components have
bolt-on port pads with square mounting hole pattern. This is not an
SAE standard; rather, it apparently originated with Vickers many
years ago and was adopted by certain other manufacturers.
Connection flanges for these ports may be purchased from the
SAE 4-Bolt Mounting Pads
|All dimensions are in
They refer to Figure 1 above.
||5/16-18 × 1-1/4
||1 × 3/4
||3/8-16 × 1-1/4
||1-1/4 × 1
||3/8-16 × 1-1/4
||1-9/16 × 1-5/16
||7/16-14 × 1-1/2
||1-3/4 × 1-1/2
||1/2-13 × 1-1/2
||2-1/8 × 1-7/8
||1/2-13 × 1-1/2
||2-1/2 × 2-1/4
||1/2-13 × 1-3/4
||3 × 2-3/4
||5/8-11 × 1-3/4
||3-5/8 × 3-3/8
||5/8-11 × 2
||4-1/8 × 3-7/8
||5/8-11 × 2
||4-5/8 × 4-3/8
||5/8-11 × 2-1/4
||5-5/8 × 5-3/8
*Length shown is
minimum. †All O-rings are
High Pressure SAE 4-Bolt Mounting Pads
Pressure rating all sizes: 6,000 PSI (414 bar). O-ring sizes are
the same as for the low pressure series. Dimensions refer to Figure 1 on
front side of sheet.
||5/16-18 × 1-1/2
||3/8-16 × 1-1/2
||7/16-14 × 1-3/4
||1/2-13 × 2-1/4
||5/8-11 × 2-3/4
||3/4-10 × 3
||7/8-9 × 3-1/2
||1-7/8-7 × 4-1/2
Several types of fittings use an O-ring as the sealing element.
These types include the SAE 4-bolt rectangular flange, the SAE and
the AND straight thread fittings, and certain proprietary types
such as the 4-bolt square flange. The following chart, published by
Aeroquip, gives the compound material considered best for the
listed fluid over the temperature range shown.
||-65 to +275°F
||Air, gasoline, mineral oil, water, JP-4, J-5, MIL-L-7808C,
||-65 to +250°F
||Steam, Pydraul, Skydrol
||-40 to +200°F
||Ammonia, hydrochloric acid, methyl alcohol, sodium hydroxide,
||-65 to 300°F
||Salt water, Freon 12, Freon 22, MIL-L-7808C
||-85 to 550°F
||Gases, hot air, high aniline oils
||-100 to 500°F
||Acids, alkalies, gases, steam, Pydraul, Skydrol
||-40 to +450°F
||Air, exhaust gases, MIL-O-8200, MIL-O-8515, MIL-H-7808C, OS45,
DC200, JP-4, JP-5
Recommended minimum spacing between holes for tool clearance, for
pipe thread or straight thread portholes.
Download a PDF of Fluid
Power Design Data Sheet 59 - Dimensions of SAE Port
© 1990 by Womack Machine Supply Co. This
company assumes no liability for errors in data nor in safe and/or
satisfactory operation of equipment designed from this