Cutting, Bending and Flaring Tubing   Article and Photos by Jim Clark

What: Cutting, bending and flaring tubing is a skill that should be mastered by anyone building or modifying a hot rod.  There are three types of tubing used in automotive applications: rigid, semi-rigid and flexible.  Rigid tubing includes JIC steel, stainless steel, titanium, heavy-walled steel, hard drawn copper, or similar types.  Semi-rigid tubing includes soft copper, brass, aluminum, thin-wall steel or special alloy.  Flexible tubing is usually called hose.  In automotive applications the cutting, bending and flaring will usually be restricted to rigid stainless or semi-rigid thin-wall steel used in brake lines.  Aluminum, soft copper or thin-wall steel for fuel, cooler, A/C and power steering plumbing lines.

How:  Rigid tubing is usually supplied in straight lengths, semi-rigid tubing in coils

Uncoiling Tubing:  Care should be taken when uncoiling tubing.  Determine how much tubing is needed, then place the coil on a bench or on the floor and hold the end with one hand.  Unroll the coil straight back without pulling it out sideways from the coil as this will put a twist in it and tend to throw it out of round.

Straightening Tubing:  Careful uncoiling still usually results in some kinking of the tubing requiring straightening.  One method is to place the tubing on a flat bench and place a flat board on top of it.  Then strike the board gently to flatten down the high spots.  Care must be taken not to flatten the tubing out of round or collapse it.

Another method of straightening long lengths is to slap the tubing against the floor, turning the tubing as you progress.  Two people are usually needed to do this, but one can do it if they secure the other end.

Cutting Tubing:  A tubing cutter is usually the safest and best way to cut thin-wall tubing.  Other methods have a number of disadvantages, the primary one being the difficulty in getting a perpendicular cut.  Exceptions to this rule are stainless and titanium tubing.  These are work hardened by a tubing cutter making the flaring process more difficult.  A hacksaw is the preferred tool for cutting this type of tubing.  Getting a perpendicular cut is difficult without the use of a sawing vise.  This is especially true for heavy wall or large diameter tubing.


aFlaring saw1

:  A sawing vise is the preferred way to get a clean perpendicular cut, especially on high strength, heavy wall or large diameter tubing. 

When a tubing cutter is used properly it will provide a clean right-angle cut with very little burr inside the tube.  To accomplish this the cutter should be fed slowly in small increments while revolving the tool around the tube.


Tubing cutters are available in a variety of sizes.  Mini cutter on the right is useful for cutting tubing within confined spaces


Some cutters have interchangeable cutting wheels to allow for the cutting of harder tubing like stainless. 

Reaming Tubing: It is desirable to remove the burr created in the end of the tubing after it is cut.  The softer the tube the more pronounced the burr will be.  Feeding the cutter in very small amounts during each revolution of the cutter will help to minimize the burr but will not eliminate it.  So the use of the reamer usually included on the cutter will usually remove the burr.  Care must be taken not to over-ream the end of the tube because this can create a weak flare due to the thinning of the metal.  Any tool used to ream the tube should be held square to the tube and pointed down to avoid getting chips in the tube.


Most tubing cutters also have a reamer attached to remove the burrs created inside the tube when it is cut


A tapered reamer can be used but care must be taken not to cut into the tubing reducing the wall thickness, which would weaken the flare


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