Hydraulics & Fluid Power Reference Library · Technical Reference

Tube Fittings (Flare, Bite-Type, Weld)

Hydraulic tube is joined by flared, bite-type (flareless) or welded and brazed fittings. This sheet explains each method, how to tell them apart and what the tube end needs before assembly.

Ref HY-0022SAE J514ISO 8434-1

Draft, open for review. Check every value against the governing standard and the manufacturer’s data before use.

What it is

Rigid steel or stainless tube is used where hose is not needed. The tube end must be joined to a fitting body in one of three main ways. Flared fittings form the tube end into a cone that seats against the fitting nose. The 37° flare (JIC) in SAE J514 is the common hydraulic flare. The 45° flare (SAE J512) is used in automotive and low-pressure refrigeration and fuel lines. Bite-type (flareless) fittings use a ferrule or cutting ring that bites into the outside of the tube when the nut is tightened. The 24° cone fitting in ISO 8434-1 (DIN style) is the common metric bite-type. Weld and braze fittings join the tube by socket welding, butt welding or brazing a sleeve, as with some O-ring face seal (ORFS) tube ends.

How to identify

Look at the tube end. A flared end shows a cone formed in the tube. A bite-type end has a ring or ferrule on the tube behind the nut. A welded end shows a weld bead at the fitting. Check the fitting nose angle with a seat angle gauge. See the seat angle identification chart and the metric L and S series fitting chart.

Tube joining methods

Method	Seal	Tube preparation	Where common
37° flare (JIC)	Metal cone to cone	Square cut, deburr, flare with 37° tool	North American hydraulics
45° flare	Metal cone to cone	45° flare tool; not for 37°	Automotive, refrigeration, fuel
24° cone bite-type	Cutting ring bites tube	Square cut, deburr, preset ring	Metric hydraulics
ORFS braze sleeve	O-ring on flat face	Braze sleeve to tube	High-pressure, leak-free systems
Socket weld	Weld	Fit-up gap, then weld	High pressure, permanent lines
Butt weld	Weld	Bevel and weld	Large tube, permanent lines

Key points

Cut tube square and remove burrs inside and out. Poor cuts cause leaks with every method.
Never mix 37° and 45° flare parts. They look alike and will leak or split.
Bite-type rings must be preset to the maker's procedure, by hand or with a presetting tool, before final assembly.
Use tube material, wall and hardness that the fitting maker allows for the method. Hard tube may not flare or bite correctly.
Tightening methods (turns from finger tight or flats) and pressure ratings are in the fitting maker's data.

Common mistakes

Using a 45° double flare tool on hydraulic tube.
Reusing a cutting ring on a new tube.
Flaring stainless tube with a tool rated only for soft tube.
Leaving the tube cut at an angle.

Governing standards: SAE J514 (37° flare and flareless tube fittings); SAE J512 (automotive tube fittings); ISO 8434-1 (24° cone fittings); SAE J1453 (O-ring face seal).

Reference only. Verify against the current governing code or standard, the manufacturer's data and the project documents before use. Apps for Distributors disclaims liability arising from reliance on this reference.

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