Choosing the correct plastic welding rod size is important because rod diameter affects filler volume, handling, welding speed and nozzle selection. The rod must also be made from a thermoplastic compatible with the material being welded.
Common Plastic Welding Rod Sizes
Smaller diameter for detail work, smaller joints and controlled filler placement.
A common general-purpose diameter for many hot air and speed welding applications.
Larger diameter that supplies more filler material per unit length for suitable larger joints.
Plastic Welding Rod Size Chart
| Rod Size / Profile | Shape | Typical Consideration | Equipment Consideration |
|---|---|---|---|
| 3 mm | Round | Smaller joints, detail work and lower filler volume | Use a nozzle suitable for 3 mm rod when speed welding |
| 4 mm | Round | General thermoplastic fabrication and repair | Use equipment and nozzle designed for 4 mm rod |
| 5 mm | Round | Larger joints and greater filler volume | Requires equipment capable of properly heating the larger rod |
| Triangle | Triangular | Specific joint designs and fabrication procedures | Match the triangle profile to the nozzle or welding method |
| Custom | Application Specific | OEM, production and specialty applications | Equipment may require a custom-compatible profile |
3mm Plastic Welding Rod
3mm plastic welding rod is a smaller round filler profile commonly used where precise filler placement or a smaller weld bead is desired.
Potential uses include:
- Smaller plastic repairs
- Detail fabrication
- Smaller grooves
- Thin thermoplastic components
- Applications requiring lower filler volume
When using a speed welding nozzle, the nozzle should be designed to properly accept and guide 3mm round rod.
4mm Plastic Welding Rod
4mm plastic welding rod is a common round size for thermoplastic fabrication and repair.
It provides more filler material than 3mm rod while remaining manageable with many handheld plastic welding tools.
4mm rod may be used for:
- General plastic fabrication
- Hot air plastic welding
- Speed welding
- Tank fabrication
- Sheet fabrication
- Plastic repair
- Industrial thermoplastic welding
5mm Plastic Welding Rod
5mm plastic welding rod has a larger cross-sectional area than 3mm or 4mm round rod and therefore supplies more filler material for each length of rod.
It can be useful for larger joints when the welding process, material thickness and equipment are appropriate.
3mm vs. 4mm vs. 5mm Welding Rod
The most obvious difference is diameter, but diameter also changes the cross-sectional area and the amount of plastic contained in each inch or foot of rod.
| Diameter | Cross-Sectional Area | Relative Filler Volume |
|---|---|---|
| 3 mm | About 7.07 mm² | 1.00 × |
| 4 mm | About 12.57 mm² | About 1.78 × a 3mm rod |
| 5 mm | About 19.63 mm² | About 2.78 × a 3mm rod |
This means that increasing diameter produces a substantial increase in filler volume. A 5mm round rod contains approximately 2.78 times the cross-sectional material of a 3mm round rod.
Plastic Welding Rod Metric to Inch Conversion
Plastic welding rod is frequently specified in millimeters, while some U.S. fabricators work with inch dimensions.
| Metric Diameter | Exact Inch Conversion | Approximate Inch Size |
|---|---|---|
| 3 mm | 0.1181 in. | Approximately 1/8 in. |
| 4 mm | 0.1575 in. | Approximately 5/32 in. |
| 5 mm | 0.1969 in. | Approximately 3/16 in. |
| 5.7 mm | 0.2244 in. | Approximately 7/32 in. |
Round Plastic Welding Rod
Round plastic welding rod is one of the most common profiles used in thermoplastic welding.
Round rod can be:
- Hand fed
- Used with a speed welding nozzle
- Supplied in straight lengths
- Wound onto coils
- Wound onto spools
- Produced in custom diameters
Common round welding rod sizes include 3mm, 4mm and 5mm.
Triangle Plastic Welding Rod
Triangle plastic welding rod has a triangular cross section rather than a circular cross section.
Triangle rod is used in particular thermoplastic fabrication applications where the joint design, welding technique or equipment is designed around a triangular filler profile.
Triangle welding rod can be produced in different dimensions and materials depending on the application.
When replacing an existing triangle rod, measure or identify the actual profile rather than assuming all triangle welding rods have the same dimensions.
5.7mm Triangle Welding Rod
A 5.7mm triangle welding rod is one example of a specialized triangular profile used in thermoplastic fabrication.
Unlike round rod, a triangle profile cannot be completely described by a single diameter. The actual profile can involve:
- Overall width
- Overall height
- Corner radii
- Angles
- Dimensional tolerances
For OEM replacement or custom manufacturing, an actual sample, drawing or verified profile dimensions are preferred.
Round vs. Triangle Plastic Welding Rod
| Feature | Round Rod | Triangle Rod |
|---|---|---|
| Cross Section | Circular | Triangular |
| Common Identification | Diameter | Profile dimensions |
| Common Sizes | 3mm, 4mm, 5mm and custom | Application-specific dimensions |
| Speed Nozzle | Match nozzle to diameter | Match nozzle to triangle profile |
| Custom Manufacturing | Custom diameters possible | Custom profile tooling possible |
Does Welding Rod Size Affect Welding Speed?
Yes. Rod diameter changes how much thermoplastic filler must be heated and deposited into the joint.
A larger rod:
- Contains more material per unit length
- Requires more heat to properly soften the filler volume
- Can fill a larger joint more quickly when equipment capacity is sufficient
- May require a different nozzle
- May require a different travel speed
The objective is not simply to use the largest possible rod. The welding process should be matched to the joint.
Does Welding Rod Size Affect Welding Temperature?
Rod diameter can affect the amount of heat required to bring the filler material into the proper welding condition, but diameter is only one variable.
Other variables include:
- Polymer type
- Material grade
- Welding tool
- Airflow
- Nozzle geometry
- Material thickness
- Travel speed
- Ambient conditions
See our Plastic Welding Temperature Chart for more information.
Plastic Welding Rod Spools
Plastic welding rod can be wound onto spools to make storage, handling and continuous feeding easier.
Spool packaging can be useful for:
- Production welding
- Industrial fabrication
- Distributor inventory
- OEM manufacturing
- Extrusion welding support applications
- Field repair
New Image Plastics Manufacturing commonly produces welding rod on 1 kilogram / 2.2 pound spools.
Actual footage per spool varies because different polymers have different densities and larger-diameter rod contains more material per foot.
Plastic Welding Rod Coil vs. Spool
Welding rod may be packaged as loose coils, straight lengths or wound onto spools.
Spools can provide several handling advantages:
- Reduced tangling
- Controlled feeding
- Convenient storage
- Easy material identification
- Production-friendly handling
How Much Plastic Welding Rod Is on a Spool?
The length of welding rod on a spool depends on:
- Spool weight
- Rod diameter
- Rod profile
- Polymer density
- Manufacturing tolerance
Because these variables change the weight per foot, there is no single footage number that applies to every 1 kg spool of plastic welding rod.
How to Choose the Correct Welding Rod Size
Consider these factors before selecting a rod diameter:
- Identify the base thermoplastic.
- Select a compatible filler material.
- Determine the joint design.
- Consider the thickness of the parent material.
- Determine the filler volume required.
- Check the welding tool capacity.
- Match the speed nozzle to the rod diameter or profile.
- Establish suitable welding conditions.
- Test the procedure before production when appropriate.
Plastic Welding Rod Size and Nozzle Selection
When using a speed welding nozzle, the welding rod must feed properly through the nozzle.
A nozzle designed for 3mm round rod may not properly accommodate 5mm rod. Likewise, a round speed nozzle should not automatically be used with a triangle profile.
The nozzle, rod and welding procedure should function as a system.
Learn more in our Plastic Welding Tools Guide.
Welding Rod Sizes by Plastic Material
Several thermoplastic families can be manufactured as welding rod in common round sizes and specialty profiles.
| Material | Common Welding Rod Options | Material Guide |
|---|---|---|
| HDPE | Round and custom profiles | HDPE Welding Rod |
| Polyethylene | 3mm, 4mm, 5mm and specialty profiles | Polyethylene Welding Rod |
| Polypropylene | Round, triangle and custom profiles | Polypropylene Welding Rod |
| PVC | Round and specialty profiles | PVC Welding Rod |
| PVDF | Round and specialty profiles | PVDF Welding Rod |
| ABS | Round and custom profiles | ABS Welding Rod |
| PETG | Round and custom profiles | PETG Welding Rod |
| TPU | Round and custom profiles depending on grade | TPU Welding Rod |
HDPE Welding Rod Sizes
HDPE welding rod can be produced in several round diameters for fabrication, repair and extrusion welding support.
Common searches include:
- 3mm HDPE welding rod
- 4mm HDPE welding rod
- 5mm HDPE welding rod
- HDPE welding rod spool
- HDPE plastic welding rod
See the complete HDPE Welding Rod Guide.
Polypropylene Welding Rod Sizes
Polypropylene welding rod is commonly produced in round and triangle profiles.
Common searches include:
- 3mm polypropylene welding rod
- 4mm PP welding rod
- 5mm polypropylene welding rod
- PP triangle welding rod
- polypropylene welding rod spool
See Polypropylene Welding Rod.
PVC Welding Rod Sizes
Rigid and flexible PVC welding rod can be produced in different sizes, but the PVC formulation must also be matched to the parent material.
See PVC Welding Rod.
PVDF Welding Rod Sizes
PVDF welding rod can be produced in round diameters and specialty profiles for chemical-resistant and industrial thermoplastic fabrication.
See PVDF Welding Rod.
Custom Plastic Welding Rod Sizes
Standard 3mm, 4mm and 5mm rod does not cover every fabrication requirement.
Custom extrusion can be used to manufacture:
- Custom round diameters
- Triangle welding rod
- Specialty profiles
- OEM replacement profiles
- Customer-specified dimensions
- Custom colors
- Special resin grades
For custom production see Custom Plastic Welding Rod.
Plastic Welding Rod Manufacturer
HotAirWelder.com is operated by New Image Plastics Manufacturing, a U.S. thermoplastic extrusion manufacturer with decades of plastic extrusion experience.
New Image Plastics manufactures welding rod in materials including:
- LLDPE
- LDPE
- MDPE
- HDPE
- HMWPE
- Polypropylene
- Rigid PVC
- Flexible PVC
- PVDF
- PETG
- ABS
- TPU
- Other thermoplastic materials
Production capabilities include 3mm, 4mm and 5mm round rod, triangle profiles, specialty profiles, custom colors, spool packaging, private labeling and OEM production.
For manufacturer-direct information visit PlasticWeldingRod.com.
Frequently Asked Questions About Plastic Welding Rod Sizes
What is the most common plastic welding rod size?
3mm, 4mm and 5mm are common round plastic welding rod diameters. The best size depends on the joint, material thickness, equipment and welding process.
Is 4mm welding rod approximately 5/32 inch?
Yes. 4mm converts to approximately 0.1575 inch, which is very close to 5/32 inch. However, an exact 4mm specification should not automatically be replaced with a fractional-inch product.
Is 3mm welding rod approximately 1/8 inch?
3mm equals approximately 0.1181 inch, while 1/8 inch equals 0.125 inch. They are close but not dimensionally identical.
Is 5mm welding rod approximately 3/16 inch?
5mm equals approximately 0.1969 inch, while 3/16 inch equals 0.1875 inch. They are similar but not identical dimensions.
Can I use 5mm rod instead of 4mm?
Only if the welding equipment, nozzle, joint and procedure are suitable for 5mm rod. The larger rod contains significantly more filler material and may require different welding conditions.
Does the speed welding nozzle have to match the rod?
Yes. A speed welding nozzle should be designed for the diameter or profile of the welding rod being used.
What is triangle welding rod?
Triangle welding rod is thermoplastic filler material extruded with a triangular rather than circular cross section. It is used for specific joint designs and fabrication processes.
Can plastic welding rod be custom sized?
Yes. Thermoplastic extrusion manufacturers can produce custom diameters and profiles when tooling, material and production requirements are suitable.
Can plastic welding rod be supplied on spools?
Yes. Plastic welding rod is commonly supplied on spools for convenient handling, storage and continuous feeding.
Related Plastic Welding Guides
- Plastic Welding Rod
- Plastic Welding
- HDPE Welding Rod
- Polyethylene Welding Rod
- Polypropylene Welding Rod
- PVC Welding Rod
- PVDF Welding Rod
- ABS Welding Rod
- PETG Welding Rod
- TPU Welding Rod
- Plastic Welding Temperature Chart
- How to Weld Plastic
- Hot Air Plastic Welding
- Extrusion Welding
- Plastic Welding Tools
- Plastic Welding Troubleshooting
- Custom Plastic Welding Rod
- Plastic Welding Rod Manufacturer
Need a Specific Plastic Welding Rod Size?
New Image Plastics Manufacturing produces plastic welding rod for industrial fabricators, distributors, OEMs and repair applications.
Available manufacturing capabilities include 3mm, 4mm and 5mm round welding rod, triangle rod, custom profiles, custom colors and spool packaging in a variety of thermoplastic materials.
Phone: 330-854-3010
Email:
newimageplastics@sbcglobal.net