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. Thread shown: 3/4-16 UNF.
The same shape as a 37 degree flare but visibly blunter - a wider, shorter cone. Side by side the difference is obvious; alone it is not.
Where it seals: Metal to metal, cone against the flared tube. No O-ring, no sealant.
Dimensions
Thread size, pitch and diameters for 1/2 in SAE 45.
Designation
1/2 in SAE 45
Thread
3/4-16 UNF
Threads per inch / pitch
16 TPI (1.587 mm pitch)
Basic major diameter (male)
19.05 mm / 0.75 in
Measured across the male crests
19.05 mm to 19.1 mm
Basic minor diameter (mating female)
17.33 mm / 0.682 in - computed from the 60 degree thread profile, not measured
Thread form
60 degree flank angle, parallel
Seat
45 degree flare cone
Tube outside diameter
0.5 in (12.7 mm)
How the size is named
Sized by tube outside diameter in inches rather than by dash number.
This size shares its thread with the JIC 37 degree flare of the same dash. The two will screw together and the joint will not seal, because a 45 degree cone meets a 37 degree cone on a line instead of a face.
Working pressure
No working pressure is published for this connection. Ratings for it vary by manufacturer, body material, port form and seal, and no two independent sources in the register give the same figure under conditions they both state. A generic number here would be a decoration, not a rating. Read the pressure from the catalogue of the fitting you are actually installing.
A fitting with two different ends is only ever as strong as the weaker end, and any rating assumes the fitting is undamaged, correctly assembled and within its temperature range. Pressure ratings are safety-relevant: confirm them against the manufacturer specification before the system is charged.
What it mates with
A female 3/4-16 UNF fitting with a 45 degree cone seat, or a 45 degree flared tube of 0.5 in outside diameter held by a flare nut.
Mating two different cone angles is the classic way to make a joint that holds pressure on the bench and weeps in service: the two cones touch on a line instead of a face, and tightening harder cold-flows the softer of the two rather than sealing it.
Do not mix these up
Fittings that measure like a 1/2 in SAE 45
Every size below sits within 0.9 mm of this one across the male thread crests, which is inside what a worn or plated fitting and a hurried measurement produce together. Those marked same thread will screw together with this fitting.
Fittings in other standards whose male thread diameter is close to 1/2 in SAE 45.
Same thread - it will screw together and the seal will be wrong
This list is computed from the published diameters in the database rather than kept as a hand-written list, so a correction to a table can never leave a stale warning behind.
Answers
Common questions about 1/2 in SAE 45
What thread is a 1/2 in SAE 45 fitting?
1/2 in SAE 45 runs a 3/4-16 UNF thread: 16 TPI (1.587 mm pitch), basic major diameter 19.05 mm / 0.75 in. Published identification charts read 19.05 mm to 19.1 mm across the male crests, which is the figure a caliper produces.
How do I tell a 1/2 in SAE 45 apart from a fitting that measures the same?
Look at the sealing surface. The same shape as a 37 degree flare but visibly blunter - a wider, shorter cone. Side by side the difference is obvious; alone it is not. Metal to metal, cone against the flared tube. No O-ring, no sealant. The thread is parallel (straight) and the flank angle is 60 degrees.
What does a 1/2 in SAE 45 screw into?
A female 3/4-16 UNF fitting with a 45 degree cone seat, or a 45 degree flared tube of 0.5 in outside diameter held by a flare nut.
What pressure is a 1/2 in SAE 45 rated for?
No working pressure is published here for this connection. Ratings vary by manufacturer, body material and seal, and no two independent sources in the register give the same figure under stated conditions for it. Read the rating from the catalogue of the fitting you are installing.
Dimensions are as defined by SAE J512, SAE J533. 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 3 independent published sources:
Which published source supplied each column, and what it gave.
Column
Sources
What they gave
Dash and trade size
ryco-sae, mcgill-id, gates-idchart
Three publishers agree on the eight sizes carried here. One extends the series to -14 and -16; those two are recorded as gaps.
Basic major diameter
ryco-sae, mcgill-id
The 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 diameter
gates-idchart, mcgill-id
Two identification charts, for the six sizes both carry.
Working pressure
ryco-sae, mcgill-id
Neither publisher gives a working pressure for this connection, so none is published. Ratings are per part, from the maker's catalogue.