ProMoly®: Seamless 4130 Steel Tubing

promoly

Industry-Leading Chromoly Tubing

Plymouth® has been a manufacturing leader since 1924. Building on this century of expertise, our team has set the industry standard for chromoly steel tubing since the 1960s. The proprietary controls governing the annealing process of our ProMoly® seamless 4130 steel tubing yield a clean, uniform surface finish, with limited oxidation and decarburization. This significantly reduces welding preparation time and ensures material consistency.

Our ProMoly® 4130 seamless tubing is engineered to the highest standards and manufactured to AMS-T-6736B, MIL-T-6736B, and AMS-6360 specifications.

Angle Grinder being used on metal

Industry-Leading Chromoly Tubing

Plymouth® has been a manufacturing leader since 1924. Building on this century of expertise, our team has set the industry standard for chromoly steel tubing since the 1960s. The proprietary controls governing the annealing process of our ProMoly® seamless 4130 steel tubing yield a clean, uniform surface finish, with limited oxidation and decarburization. This significantly reduces welding preparation time and ensures material consistency.

Our ProMoly® 4130 seamless tubing is engineered to the highest standards and manufactured to AMS-T-6736B, MIL-T-6736B, and AMS-6360 specifications.

Trust the Source, Specify ProMoly®

exceptional qualities are valued for performance racing and aerospace applications. The dimensional consistency and outer diameter (OD) uniformity of ProMoly® seamless tubing help reduce setup time and ensure repeatable construction, providing builders a superior alternative to traditional 4130 tubing. ProMoly® affords the strength, consistency, and performance required for modern engineering and fabrication.

The characteristics of ProMoly® valued throughout various markets entail:

  • Higher Strength-to-Weight Ratio: Chromium and molybdenum deliver higher tensile strength and toughness compared to carbon tubing.
  • Exceeds Industry Standards: Our manufacturing and annealing practices surpass the industry requirements for standard 4130 tubing.
  • Fatigue Resistance: With its excellent durability under repeated impact and vibration, ProMoly® tubing is ideal for high-stress applications.
  • High Elongation Values: ProMoly® 4130’s enhanced ductility supports tight radius bending and shaping without fracturing.
  • Consistent Mechanical Properties: Our precision annealing procedure yields uniform tubing with predictable welding performance and minimal distortion.

ProMoly® is a registered trademark of Plymouth®.

Product Specifications

MeasurementInches/FeetMetric
OD Range0.250” – 2.000”6.35mm – 50.8mm
Minimum OD Tolerance+/- 0.005” (up to 1.500” OD)+/- 0.127mm (up to 38.1mm)
Maximum OD Tolerance+/- 0.10” (above 1.500” OD)+/- 2.54mm (above 38.1mm)
Wall Range0.025” – 0.187”0.635mm – 4.75mm
Minimum Wall Tolerance+/- 10% (For IDs over 0.500”)+/- 10% (For IDs over 12.7mm)
Maximum Wall Tolerance+/- 15% (for IDs under 0.500”)+/- 15% (for IDs under 12.7mm)
Maximum Length26’7.9m

Industry Specifications and Certifications

  • Grade: 4130
  • Industry Specifications: AMS-T-6736A | AMS-6371 | AMS-6360 | MIL-T-6736B
  • Certifications: ISO 9001

Industrial Applications

Aerospace Tubing

ProMoly®’s dimensional consistency and ability to maintain performance in high-stress applications is highly valued for manufacturing seamless aerospace tubing, and its performance specifications surpass AMS standards.

Markets for ProMoly® 4130 Tubing

Performance Racing

Performance Racing

ProMoly® 4130 Cold Drawn Seamless Tubing is one our Plymouth Motorsports Products™ and is the preferred chromoly tubing for builders across the racing spectrum, including sprint car, dragster, motorcycle, formula, stock car, and numerous other racing applications. Prized by manufacturers and racing engineers, ProMoly® is used to construct components including:

  • Chassis
  • Frames
  • Rollbars
  • Steering components
  • Suspension components
Defense

Defense

Chromoly tubing is widely used in the defense market for applications requiring structural integrity and lower weight. This includes a variety of ground systems and defense equipment.

  • Tactical and armored vehicle frames and substructures
  • Roll cages and occupant protection systems
  • Weapon system mounts and support components
  • Platform components for missiles, launchers, and radar
  • Mobility platforms, trailers, and other transport systems
Transportation

Automotive

The strength-to-weight ratio, clean weldability, and high fatigue resistance that render 4130 seamless tubing valuable in performance racing are equally applicable to the transportation market. ProMoly® is used extensively in automotive manufacturing due to its performance, reliability, and consistency. Common automotive applications for chromoly tubing include:

  • Roll cages and safety structures
  • Chassis and space frames
  • Suspension control arms and linkages
  • Structural supports for high-strength tubular builds
Recreational

Recreation

Similarly, ProMoly®’s structural characteristics provide a balance of durability, ride performance, and strength for recreational vehicles, allowing them to better withstand jumps, uneven terrain, and delivering enhanced performance and flexibility for better handling and ride quality. Specifically, ProMoly® is used to construct:

  • Motorcycle frames for off-road, racing, and street applications
  • Frames for BMX, mountain, and touring bikes
  • Vehicle frames and roll structures for ATVs and UTVs
Automation

Automation

The strength of chromoly tubing is frequently applied in precision-engineered systems in continuous operation with dynamic loads. For industrial purposes, ProMoly® is often used to build equipment for automation processes, including:

  • Machine frames and structural bases
  • Material handling systems for conveyance and pick and place
  • Load-bearing assemblies such as equipment guards and supports
  • Robotic cell structures and enclosures
Aerospace tubing

Aerospace

Due to its superior stress resistance, high dimensional control, and repeatable construction capabilities, seamless ProMoly® is used to fabricate 4130 streamline tubing for aerospace components requiring tight tolerances that meet aircraft and military compliance standards. Some of these components include:

  • Airframe and structural parts
  • Vertical stabilizer spars
  • Wing struts
  • Nacelle and engine mounts

Downloads & Resources

FileLanguageSizeDownload
ProMoly® BrochureEN3 MB Download
4130 Streamline TubingEN144 KB Download
Plymouth® Product CatalogEN4 MB Download
VideoWatch
Fabricating, Bending, Welding 4130 Tubing Watch
ProMoly® 4130 Cold Drawn Seamless Tubing Watch
Specifying ProMoly® is a Seamless Decision Watch
Eupora and FTS at Plymouth® | Manufacturing Capabilities & Facility Overview Watch

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