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Mandrel vs. Rotary Tube Bending: How to Choose the Right Method for Your Project
- PSI Hydraulics
- 3 days ago
- 4 min read
In precision metal fabrication, the way a tube is bent can determine everything from strength and safety to cost and efficiency. Two of the most common methods—mandrel tube bending and rotary (or rotary draw) tube bending—each offer distinct advantages depending on your application. Understanding which is best suited for your project isn’t just helpful—it’s essential.
This guide breaks down how each method works, when and why you’d use one over the other, and how PSI Hydraulics applies these techniques to deliver reliable, high-performance results across industries.
What Is Mandrel Tube Bending?
Mandrel tube bending is a process that uses a mandrel—a metal rod or ball inserted into the tubing during bending—to support the interior walls and prevent collapse or wrinkling. This method is ideal for maintaining the integrity of tubes with thin walls or those requiring tight radius bends.
Key Benefits of Mandrel Bending:
High precision: Maintains a smooth, round cross-section without deformation
Tight radii capability: Ideal for space-constrained environments
Smooth interior flow: Essential for fluid or gas transfer systems
Better structural integrity: Especially in safety-critical applications
Drawbacks:
More complex setup: Tooling and alignment take time
Higher upfront cost: Particularly for low-volume runs
Mandrel bending is commonly used in industries where precision and performance are non-negotiable—like aerospace, oil & gas, and high-pressure hydraulic systems.
What Is Rotary Tube Bending?
Rotary tube bending, often called rotary draw bending, uses a die set to draw the tube around a bend radius. It does not include internal support like a mandrel, which makes it better suited for thicker-walled tubes and larger bend radii.
Key Benefits of Rotary Bending:
Faster production: Especially on medium to high-volume jobs
Lower tooling cost: Simpler setup for general-purpose parts
Effective for sturdy materials: Like carbon steel and stainless
Drawbacks:
Less suitable for tight bends: Deformation risk increases with radius tightness
May cause wrinkling or ovalization: Especially in thinner or softer tubing
Rotary bending works well in construction equipment, general fabrication, and applications where tolerance is important but not as critical as in aerospace or fluid systems.
Comparison Table: Mandrel vs. Rotary Bending
How to Choose the Right Bending Method
Selecting the right bending process depends on a combination of technical and practical factors. Here’s how to evaluate your project:
1. Wall Thickness
Thin-walled tubing (especially under 0.065") almost always benefits from mandrel bending due to its susceptibility to deformation. For thicker walls, rotary bending may be faster and more cost-effective.
2. Bend Radius
Tight bends (less than 2x the tube diameter) usually require a mandrel to maintain structural integrity. Larger, more relaxed bends may not.
3. Material Type
Aluminum and stainless steel: Often require mandrel support
Carbon steel and copper: More tolerant to rotary bending
4. Application Demands
If your tubing carries hydraulic fluid, gas, or is part of a high-pressure or structural system, precision is critical—and mandrel is the clear choice. For general framework or conduit routing, rotary is often sufficient.
5. Production Volume
Low-volume custom projects may justify the higher tooling investment for mandrel bending, especially when precision matters. For repeat runs of more forgiving parts, rotary keeps costs down.
Real-World Use Cases
Oil & Gas
Mandrel bending is essential here due to high-pressure lines and compact installations. PSI Hydraulics regularly supports downstream and offshore operations with precision-formed stainless steel and coated steel tubing.
Construction Equipment
Rotary bending is often the go-to method for fabricating protective frames, hydraulic tube runs, and structural components in heavy machinery. It balances speed with sufficient accuracy.
Rail Systems
Passenger and freight rail systems demand safety, consistency, and tight tolerances—making mandrel bending a key requirement for hydraulic and brake system lines.
Custom Fabrication & Prototyping
When the job calls for unique dimensions, non-standard materials, or compact assemblies, PSI's hybrid capabilities allow us to choose the ideal method based on your specs—not our equipment.
Optimizing Tube Bending for Industrial Projects
At PSI Hydraulics, we don’t take a one-size-fits-all approach. Every project gets an engineering review to match material, dimensions, and application with the right bending process.
We work with steel, aluminum, stainless, copper, and specialty alloys
Bend up to 2" diameter tubes
Offer CNC-controlled precision for repeatability
Provide both in-house and mobile support for urgent or field-based work
This ensures you get a clean, strong, high-performing result—no guesswork involved.
Let’s Get Your Tube Bending Right
Choosing between mandrel and rotary bending isn’t just a technical decision—it’s about performance, reliability, and cost control. At PSI Hydraulics, we guide you through that decision with practical experience and engineering know-how.
Need precision tube bending for your next project? Contact our team to speak with a bending specialist.
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