Tube Flaring Tools: Complete Types, Angles & Selection Guide
A complete map of tube flaring tools by flare geometry (45° SAE, 37° JIC, double, bubble), drive type (concentric/eccentric) and tube size, with a selection framework and the leak-prevention workflow.
Tube Flaring Tools: A Map of the Whole Family
A flare forms a cone on the end of a tube so it seals metal-to-metal against a matching cone in a fitting. The tool must match the flare angle, tube material and wall thickness exactly; a mismatch here is a leak you discover only after pressurisation. This page maps the family by geometry and drive, then gives the selection and leak-prevention workflow. For a purchase decision start with the copper tube flaring tool buying guide; for the supply side see our flaring tool manufacturer page.
The Full Type Map
By flare geometry
- 45° SAE single flare — the standard for HVAC, refrigeration, plumbing and gas copper lines.
- 37° JIC — hydraulics; the cone does not match 45° SAE.
- Double flare — the tube end is folded back first, doubling the wall at the seat for high-pressure, high-vibration and brake lines. See single flare vs double flare.
- Bubble / DIN flare — a rounded seat used on some European brake lines; needs its own die.
By drive / forming method
- Concentric (flat-clamp) yoke — the standard workshop tool, fine for soft copper.
- Eccentric cone — sweeps circumferentially, forming a more uniform cone on thin-wall and aluminium tube; preferred for premium HVAC. See the CT-806A eccentric 45° flaring tool and the FT-806AM-F eccentric kit.
By size coverage
Common line-set dies are 1/4, 3/8, 1/2 and 5/8 in; metric kits mirror these. Imperial vs metric mismatch is a classic source of leaks, covered in inch vs metric flaring tools. Our CT-190A/190M, CT-191A/191M, CT-203A/203M and CT-103A/103M sets cover the size spread, with flaring tool accessories for dies and spares.
Selection Framework
Variable | Check | Direction |
|---|---|---|
Fitting angle | 45° SAE or 37° JIC? | Match the die exactly; never force one into the other. |
Tube material | Soft copper, thin-wall, aluminium? | Thin-wall/aluminium → eccentric tool. |
Pressure & vibration | Stationary low-pressure or pulsing high-pressure? | Pulsing/high-pressure → double flare. |
Size system | Imperial or metric tube? | Match the die to tube OD, not the fitting. |
The Workflow That Prevents Leaks
- Cut square with a wheel cutter such as the copper tubing cutter.
- Ream and deburr both faces — a burr scores the cone and starts a crack.
- Anneal work-hardened copper locally before forming.
- Clamp at the correct protrusion and form to the matched die.
- Tighten the nut firm plus roughly a quarter turn; no sealant on flare threads.
- Pressure-test and evacuate with a micron gauge before charging.
The full walkthrough is in how to make a leak-free HVAC flare. For joints where a flare is not the right answer, see flare fitting vs compression fitting. Cutting, bending and swaging sit alongside flaring in tube working tools, the cutter & bender guide and our tube bender manufacturer page.
From Selection to Purchase
Once the geometry and drive are fixed, the remaining work is specification and approval. Our RFQ specification checklist and sample approval checklist turn the technical choice into a sourcing document. Detailed specifications, certifications, MOQ and capacity are available on request.
Failure Modes: Diagnosing a Bad Flare
Off-centre flare from a worn clamp bar
If the flare cone is visibly thicker on one side, the tube slipped in the clamp bar rather than the cone being wrong. Clamp jaws wear where the tube is gripped; once polished smooth they no longer hold under the axial load of the cone. Check for movement by marking the tube at the jaw face before flaring. Replace or re-grip the bar before blaming the tool, and confirm the tube end is square and deburred.
Split flare from work-hardened or unannealed tube
A crack radiating from the flare lip means the material could not take the deformation. Half-hard copper, an old cut end, or a tube that has already been bent close to the end will split. Anneal the end where the specification allows, cut back to fresh material, and use an eccentric cone that forms by rolling rather than pressing. Single vs double flare explains where the extra fold is required and where it is not.
The 45° / 37° mismatch that never seals
A 45° SAE flare and a 37° JIC flare look similar on a bench. They do not share a seating angle, and no amount of torque will make the pair seal. Likewise, inch and metric dies that are nominal-equivalent but not exact leave an undersized seat. Inch vs metric sizing is worth reading before a mixed-market order is placed. Flare vs compression fittings covers the cases where a flare is the wrong joint altogether.
Specification Checklist Before You Order
Field | What to specify | Why it matters |
|---|---|---|
Flare angle | 45° SAE (refrigeration) or 37° JIC | Not interchangeable; determines fitting compatibility |
Tube OD set | Inch, metric, or both; list every required size | One missing die blocks a job family |
Cone type | Fixed 45°, eccentric rolling, or double-flare adapter | Affects work hardening and finish quality |
Tube condition | Soft / half-hard copper, aluminium, thin-wall steel | Harder material may need annealing |
Clamp & die spares | Replacement jaws, cones, adapters | Wear items dominate long-term cost |
Inspection | Angle gauge, seat-width check, sample approval record | Defines an objective accept/reject standard |
Use the RFQ specification checklist to send these fields together, and the sample approval checklist to lock a golden sample before bulk production. Certificates are available on request.
Setting Up a Repeatable Flare Station
Consistency on flares comes from the bench, not from the operator's wrist. Fix the clamp bar to a rigid surface, align the yoke so the cone axis is exactly perpendicular to the clamp face, and keep a single dedicated light source at a low angle — a low-angle light makes a hairline split visible in a way overhead lighting does not. Keep the dies and cone clean; a single brass chip trapped in a die produces a seat defect that looks like a material problem.
Use one tube protrusion gauge for the whole shift and mark the setting on it. Protrusion height is the variable most often adjusted by feel, and it directly controls flare diameter: too little gives an undersized seat, too much stretches and thins the lip. A light, consistent film of the correct lubricant on the cone reduces pickup; excess lubricant contaminates the joint. Log the die size, tube batch and protrusion setting on the first and last flare of each run.
Keep a rejected sample next to an accepted one. New operators learn the accept/reject boundary far faster from two physical parts than from a written tolerance, and the same pair makes a useful golden-sample reference when a sample approval is agreed with a supplier. For higher-volume work the large-size flare tools and the HVAC distributor buying guide cover the equipment step-up.
Frequently Asked Questions
What are the main types of flaring tool?
By geometry: 45° SAE single flare, 37° JIC, double flare and bubble/DIN flare. By forming method: concentric flat-clamp yokes and eccentric cone tools. Kits are then differentiated by the tube sizes (1/4–5/8 in or metric equivalents) their dies cover.
How do I choose between concentric and eccentric?
Concentric is fine for standard soft copper. Eccentric forms a cleaner, more uniform cone on thin-wall and aluminium tube and is preferred for premium HVAC and variable-refrigerant work. Our flaring tool buying guide compares them in detail.
Can one flaring tool cover 45° and 37° fittings?
Only if it ships both die/cone sets, and you must swap them per fitting. The cones are not interchangeable — a 45° flare in a 37° JIC seat will leak. Confirm the fitting angle before forming.
More Questions Buyers Ask
Can a flare be re-made on the same tube end?
Not reliably. Re-flaring work-hardens the end further and usually leaves the original seat line visible. Cut back to fresh tube, ream, and start again. On a job site the cost of a short offcut is trivial compared with a leaking joint behind a finished wall.
When is a double flare actually required?
Where the application standard calls for it — commonly higher-pressure brake and some fuel lines — because the folded seat adds material at the sealing face and resists cracking. It is not a general upgrade for refrigeration line sets; the fitting itself must be designed for that seat.
Why do two kits with the same die sizes behave differently?
Clamp bar hardness, cone geometry, and the yoke's alignment under load all vary. An eccentric cone rolls the tube and reduces the force needed; a fixed cone presses it. Ask for a sample flare on your own tube before approving a production run.
What documentation should a distributor require?
Dimensional inspection method, angle verification, die material and hardness, spare-part list and packaging proof. Capacity figures, audit reports and certificates are available on request — we specify them per order rather than publishing unverified numbers.
