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Fittings

SAE J1926-1 · ISO 11926-1

SAE straight thread O-ring boss, ORB (SAE J1926-1 / ISO 11926-1)

A straight Unified inch thread with an O-ring on a shoulder behind it, screwed into a port with a machined flat spotface. The standard port on North American pumps, valves and manifolds.

13 sizes60 degree flanksParallel threadO-ring boss (straight thread port)

Identify a fittingCompare with a lookalike
O-ring boss (straight thread port), on a parallel threadO-ring behind the threadParallel threadOpen end on the left
Schematic cross-section of the male half, upper side only, with the centre line dashed and the open end on the left. Cone angles are drawn at their true angle from the axis; nothing else is to scale and no dimension should be measured off it.

How to recognise it

A straight male thread with a plain unthreaded shoulder behind it carrying an O-ring, screwing into a port with a flat spotface at the top of the threads.

Where it seals: The O-ring squashed between the fitting shoulder and the machined spotface of the port. The thread only holds the load.

The O-ring is the seal, not the thread. Running an O-ring boss fitting into a tapered port, or torquing it down without the O-ring seated against the spotface, damages the port face and the port is then scrap.

How it is sized

Sized by dash number. The thread is identical to the JIC thread of the same dash - only the sealing end differs.

Where you will find it: Pump, motor, valve and manifold ports. Almost always the port end rather than the hose end.

Also searched as: ORB, SAE ORB, straight thread O-ring, SAE J1926, O-ring boss.

All sizes

SAE O-ring boss size table

Thread, pitch, diameters and working pressure for every SAE O-ring boss size in the database.
SizeThreadTPI / pitchBasic major ØMeasured across crestsTube / trade sizeWorking pressure
-02 SAE ORB5/16-24 UNF24 TPI (1.058 mm pitch)7.94 mm / 0.313 in7.87 mm to 7.9 mm0.125 in5,000 psi (345 bar)
-03 SAE ORB3/8-24 UNF24 TPI (1.058 mm pitch)9.53 mm / 0.375 in9.5 mm to 9.65 mm0.1875 in5,000 psi (345 bar)
-04 SAE ORB7/16-20 UNF20 TPI (1.27 mm pitch)11.11 mm / 0.438 in11 mm to 11.18 mm0.25 in4,500 to 5,000 psi (310 to 345 bar)
-05 SAE ORB1/2-20 UNF20 TPI (1.27 mm pitch)12.7 mm / 0.5 in12.5 mm to 12.7 mm0.3125 in4,000 to 5,000 psi (276 to 345 bar)
-06 SAE ORB9/16-18 UNF18 TPI (1.411 mm pitch)14.29 mm / 0.563 in14.1 mm to 14.22 mm0.375 in4,000 to 5,000 psi (276 to 345 bar)
-08 SAE ORB3/4-16 UNF16 TPI (1.587 mm pitch)19.05 mm / 0.75 in18.9 mm to 19.05 mm0.5 in4,000 to 4,500 psi (276 to 310 bar)
-10 SAE ORB7/8-14 UNF14 TPI (1.814 mm pitch)22.23 mm / 0.875 in22.1 mm to 22.35 mm0.625 in3,000 to 3,500 psi (207 to 241 bar)
-12 SAE ORB1 1/16-12 UN12 TPI (2.117 mm pitch)26.99 mm / 1.063 in26.9 mm to 26.92 mm0.75 in3,000 to 3,500 psi (207 to 241 bar)
-14 SAE ORB1 3/16-12 UN12 TPI (2.117 mm pitch)30.16 mm / 1.188 in30 mm to 30.23 mm0.875 in2,500 to 3,000 psi (172 to 207 bar)
-16 SAE ORB1 5/16-12 UN12 TPI (2.117 mm pitch)33.34 mm / 1.313 in33.2 mm to 33.27 mm1 in2,500 to 3,000 psi (172 to 207 bar)
-20 SAE ORB1 5/8-12 UN12 TPI (2.117 mm pitch)41.27 mm / 1.625 in41.2 mm to 41.4 mm1.25 in2,000 to 2,500 psi (138 to 172 bar)
-24 SAE ORB1 7/8-12 UN12 TPI (2.117 mm pitch)47.62 mm / 1.875 in47.6 mm to 47.75 mm1.5 in1,500 to 2,000 psi (103 to 138 bar)
-32 SAE ORB2 1/2-12 UN12 TPI (2.117 mm pitch)63.5 mm / 2.5 inabout 63.5 mm2 in1,125 to 1,500 psi (78 to 103 bar)

13 of the 13 sizes carry a published working pressure. Every one of them prints the exact conditions it applies under on its own page - a figure without its material and safety factor is not a rating.

On paper

Identification sheets covering SAE O-ring boss

SAE inch fittings: JIC 37, ORB, ORFS and SAE 454 sectionsSeat and thread identification: all ten standards1 sectionsPublished working pressures, with the conditions they apply under5 sections

Where these figures come from

Dimensions are as defined by SAE J1926-1, ISO 11926-1. FittingKey is an independent reference and is not affiliated with, endorsed by or approved by any standards body or fitting manufacturer.

Every value on this page was checked against 6 independent published sources:

Which published source supplied each column, and what it gave.
ColumnSourcesWhat they gave
Dash and trade sizetompkins, mcgill-id, chs-orfs, gates-idchartFour publishers, same dash-to-port-size map, and all four give the ORB thread as identical to the JIC thread of the same dash.
Basic major diametertompkins, mcgill-idThe thread designation fixes the basic major diameter: a 3/4-16 UNF thread has a basic major diameter of 0.750 in, which is 19.05 mm at 1 in = 25.4 mm exactly. The inch and millimetre columns are that one figure in two units.
Measured male thread diametergates-idchart, mcgill-idTwo identification charts, within 0.25 mm at every size.
O-ring sizeglobaloring, gates-idchartThe AS568 900-series dash number comes from the O-ring maker's table, indexed by nominal port size. It was cross-checked against the measured O-ring inside diameters printed on the coupling chart: all thirteen agree to within 0.1 mm.
Working pressuretompkins, brennan-pressureTwo catalogues, steel, 4 to 1 against minimum burst per SAE J514, each giving a separate figure for a straight stud and for an adjustable stud. Both pairs match on all thirteen sizes.