A flaring tool creates a flared, bell-shaped opening at the end of a tube. This flare lets the tube connect tightly to another fitting, stopping leaks in systems that carry fluids or gases.
The Basics of Creating Tube Flares
Using a flaring tool correctly is key for safe and long-lasting connections in plumbing, HVAC, and automotive work. Poor flares lead to leaks, which can be dangerous or cause system failure. Learning the right tube flaring techniques makes a big difference.
What You Need Before You Start
Before you begin flaring copper tubing or other soft metals, gather your gear. Good preparation stops problems later.
- The Flaring Tool Set: This usually includes a yoke (the main clamp part) and various adapters or dies.
- Tubing Cutter: A clean, square cut is vital.
- Deburring Tool or Reamer: This removes sharp edges inside and outside the tube.
- Soft Cloth: For cleaning.
- Appropriate Fittings: Make sure your fittings match the tubing size.
Preparing Tubing for Flaring
This step is often rushed, but it is critical for success. Preparing tubing for flaring takes time.
- Cut the Tube: Use a tube cutter to make a straight cut. Rotate the cutter slowly. This keeps the tube end square. A crooked cut leads to an uneven flare.
- Remove Burrs: Burrs are small bits of metal left after cutting. Use the internal reamer or an external deburring tool. Clean both the inside and outside edges of the tube end. If you skip this, the flare won’t sit right, causing leaks.
- Clean the Area: Wipe the flared section with a clean cloth. Oil or dirt prevents a tight seal.
- Check Length: Make sure the tubing is long enough to reach the fitting and create a proper flare, but not so long that it kinks when tightened.
Flaring Tool Operation: A Step-by-Step Guide
Flaring tool operation varies slightly between manual and hydraulic types, but the basic goals are the same: shape the tube end smoothly.
Single Flare Setup
The single flare is common for lower-pressure applications. Think of basic water lines or some gas setups.
Steps for a Single Flare Setup
- Set the Yoke: Place the tubing into the flaring block. The block has holes matching the tube size. Tighten the clamp screws firmly. The end of the tube should stick out slightly above the block.
- Measure Exposure: For most single flares, the tube end should stick up about 1/16 inch to 1/8 inch above the block face. Check your tool’s manual for the exact dimension.
- Attach the Flaring Cone: Screw the flaring cone (the adapter) into the center hole of the yoke. Make sure the cone tip is centered over the tube end.
- Apply Pressure: Turn the handle on the yoke clockwise. This pushes the cone down into the tube end. Turn it slowly. You will feel resistance.
- Stop and Back Off: Turn the handle until the cone stops moving down. Then, turn it back a half turn or so. This releases the pressure slightly.
- Check and Repeat: Remove the cone. The tube end should now look like a bell. If it is not fully flared, clean the area and repeat steps 4 and 5. Apply more turns in small increments until the flare takes the right shape. Do not overtighten and crack the metal.
Double Flaring Instructions
Double flaring instructions are necessary for higher-pressure lines, especially in automotive brake systems using steel or soft copper-nickel tubing. A double flare uses two steps to create a stronger, rolled lip.
Steps for Double Flaring
- First Flare (Pilot Flare): Follow the single flare setup steps above, but only tighten the cone about halfway down, or until you see a small pilot flare form. This first step shapes the metal, not the final seal.
- Prepare for the Second Flare: Back the cone all the way out. Remove the tube from the block. You will see a small, rounded lip forming.
- Flip the Tube: Flip the tube over. Put the newly flared end back into the flaring block. The pilot flare should now be sitting inside the block opening.
- Second Pass: Reinstall the cone. This time, tighten the cone much further down than the first time. This action rolls the initial flare back upon itself, creating a tight, double-layered seal edge. This is what makes the connection strong.
- Final Check: Remove the tube. The end should look like two flares stacked together, very smooth and strong. Test it against the matching fitting before installation.
Specialized Flaring Methods
Not all jobs require the standard flare nut style. Professionals often use different tube flaring techniques for specific materials or pressure needs.
Hydraulic Flaring Methods
For very hard metals or when making many flares quickly, a hydraulic flaring tool is often better. Hydraulic flaring methods use a pump to apply massive, consistent force.
- Benefits: Less physical effort. More consistent pressure for harder materials like stainless steel.
- Process: The tubing is set in the hydraulic yoke. Instead of turning a screw handle, you pump a lever until the pressure gauge hits the required PSI, or the stop mechanism engages. This offers superior control over the force applied.
Flaring Tool Adjustments for Different Materials
The hardness of the material changes how you must use the tool. Flaring tool adjustments are crucial for preventing cracks.
| Material Type | Required Flare Type | Key Adjustment / Technique | Risk if Done Wrong |
|---|---|---|---|
| Soft Copper | Single Flare | Gentle, multiple turns. Stop before the tube wall thins too much. | Cracking or splitting the flare. |
| Soft Steel/Brass | Single or Double Flare | Requires more turns than copper. Use lubrication if possible. | Incomplete flare; metal hardening unevenly. |
| Hardened Steel | Double Flare (Often specialized tool) | High, steady pressure. Very slow application of force. | Tool breakage or catastrophic tube failure. |
Best Practices for Flaring Success
To ensure every flare you make is perfect, follow these best practices for flaring. These tips come from years of experience in the field.
Choosing the Right Tool Type
There are several types of flaring tools available:
- Yoke Style (Manual): Good for DIY and occasional use with soft metals. Simple to carry.
- Ratchet Style: Faster for single flares than the basic yoke style. Uses a ratchet mechanism for easier turning.
- Hydraulic Style: Best for high volume or very hard tubing. Provides the most repeatable results.
Lubrication Matters
When flaring copper tubing or brass, a small amount of oil or specialized cutting fluid on the cone greatly helps. Lubrication reduces friction. This allows the metal to flow smoothly into the flare shape instead of tearing or binding against the tool.
Never Overwork the Metal
The most common mistake is trying to force a full flare in one go. Metal has a memory. If you push too hard too fast, the metal heats up unevenly, gets brittle, or thins out too much at the edge. Always work in stages. Apply pressure, back off slightly, and repeat. This lets the stress equalize across the metal.
Inspecting the Finished Flare
A good flare has specific traits you must check:
- Even Lip: The flare edge must be uniform all the way around. If one side is thicker or thinner, the seal will fail.
- No Cracks: Look closely for hairline cracks, especially near the base where the flare meets the straight tube section. Cracks mean the metal was overworked.
- Proper Angle: The flare angle must match the fitting it seals against (usually 45 degrees for standard fittings, 37 degrees for AN fittings). If your tool is set up correctly, this should happen automatically.
Deciphering Flare Angles and Fitting Types
Fittings are designed to mate with specific flare angles. Using the wrong angle is like trying to fit a square peg in a round hole—it won’t seal.
Common Flare Standards
| Standard Name | Angle | Common Use |
|---|---|---|
| SAE 45 Degree Flare | 45° | Standard domestic refrigeration, air conditioning, and many low-pressure fluid lines (e.g., flared copper water lines). |
| Inverted Flare | 45° (Reverse Seating) | Used often in older automotive fuel and transmission lines. The flare seats inside the fitting body. |
| Double Flare | 45° (Rolled) | High-pressure automotive brake lines (steel). |
| JIC (AN) Flare | 37° | Aerospace and high-performance automotive (high pressure, superior sealing capability). Requires a specific 37° tool set. |
If you are working on a brake line, you must use the double flare technique with a 45-degree tool set. If you are setting up an A/C line with standard flare nuts, you will use the 45-degree single flare. Always confirm the required angle based on the mating fitting.
Maintaining Your Flaring Tools
Proper care extends the life of your tools and ensures accurate results for years. Flaring tool adjustments are less frequent if maintenance is consistent.
Cleaning After Use
After using your tool, especially with oily materials, clean off all residue. Metal shavings or old lubricant can interfere with the next setup.
- Wipe down the yoke and block surfaces.
- Check the threading on the cone screw for any debris.
- If you used hydraulic fluid, check the seals periodically for leaks.
Storage Considerations
Store your flaring set in a dry place. Moisture causes rust, which ruins the precise surfaces needed for a good flare. If your set comes in a case, use it. Keep the different sized dies organized so you grab the right one immediately.
Grasping the Physics of Flaring
When you turn the handle, you are not just pushing the cone down. You are causing the metal tube to flow plastically. Plastic flow means the metal changes shape permanently without breaking.
When the cone pushes down, the pressure forces the metal outward against the walls of the block. The tube wall stretches thin, forming the lip. This stretching must be controlled. If the stretching is too fast, the material’s yield strength is exceeded, and it fractures instead of flowing. This is why slow, incremental tightening is the rule.
Flaring copper tubing is easier because copper has a low yield strength, meaning it flows easily. Harder metals require tools capable of overcoming that higher resistance.
FAQ Section
What is the main difference between a single flare and a double flare?
The main difference is the number of steps and the resulting seal strength. A single flare creates one bell-shaped edge. A double flare involves creating a pilot flare, flipping the tube, and then forcing that pilot back onto itself, creating a stronger, rolled seal ideal for high-pressure systems like brakes.
Can I use a standard single flare tool for brake lines?
No, generally you should not. Brake lines require the reliability of a double flare because they hold high, pulsating pressures. Using a single flare on a brake line is unsafe and will almost certainly lead to failure. You need a double flare kit.
How much tubing should stick out of the flaring block?
This depends on the flare type and the tool instruction manual. For a standard 45-degree single flare, typically about 1/16 to 1/8 inch (about 1.5 mm to 3 mm) sticks out above the block surface. Too little, and you won’t make a full flare; too much, and the flare edge might be too thin.
What causes a tube flare to crack during the process?
Cracking usually happens for two reasons: 1) The metal was overworked (too much pressure applied too quickly), or 2) The tubing material was too hard or brittle for the tool being used. Using proper lubrication and working in slow stages usually prevents cracking.
How do I know if my flare is good before I connect it?
A good flare looks uniform all the way around. The lip should be smooth, not jagged or cracked. When you place it against the matching fitting, it should seat perfectly flat against the cone surface of the fitting without gaps on any side.