Introduction
A customer asks for a 5 kN cable tensile tester.
At first, that sounds like enough information to select a machine. In practice, it usually is not.
Are they testing the tensile properties of the cable jacket? Breaking a finished wire? Pulling a crimped terminal from a conductor? Or checking whether a connector remains attached to a cable assembly?
All four tests involve pulling, but they do not necessarily use the same specimen, fixture, calculation method, standard, or even the same result.
Before selecting a tensile tester, the more useful question is:
What exactly needs to be measured—and what is expected to fail?
Quick Selection: What Test Do You Actually Need?
The easiest way to avoid selecting the wrong machine is to begin with the failure you are trying to evaluate.
| If Your Concern Is... | What Should Be Tested? | Main Result | Typical Setup |
|---|---|---|---|
| Insulation or jacket material strength | Prepared insulation/sheath specimen | Tensile strength, elongation | Tensile grips |
| Finished wire breaking under load | Finished wire | Breaking force | Wire or cable grip |
| Overall cable mechanical strength | Finished cable | Maximum force, displacement | Cable grip |
| Crimp quality | Wire + terminal | Pull-out force | Terminal pull fixture |
| Connector retention | Cable + connector | Separation / retention force | Connector fixture |
| Flexible polymer performance | Prepared polymer specimen | Stress, elongation | Tensile grips, strain measurement |
This table also explains why searching only for a “cable tensile testing machine” can be misleading.
A machine may have enough force capacity but still be unsuitable if the required fixture, travel, strain measurement, or test method has not been considered.
Tensile Strength, Breaking Force and Pull-Out Force Are Not the Same
These terms are often mixed together in RFQs, laboratory specifications, and equipment discussions.
They should not be treated as interchangeable.
Tensile Strength
Tensile strength is primarily a material property.
For a prepared specimen, it relates the maximum tensile force to the original cross-sectional area:
Tensile Strength = Maximum Tensile Force / Original Cross-Sectional Area
The result is commonly expressed in MPa.
This is relevant when engineers need to characterize:
- Cable insulation compounds
- Sheath compounds
- Plastics
- Elastomers
- Other non-metallic cable materials
A force value alone does not give tensile strength unless specimen dimensions are also considered.
Breaking Force
Breaking force describes the force at which a specimen or finished component fails.
For example:
A finished wire breaks at 420 N.
For many finished-product tests, this direct force measurement may be more meaningful than converting the result into MPa.
Pull-Out Force
Pull-out force is generally associated with an assembly or connection.
Examples include:
- Wire pulled from a terminal
- Terminal pulled from a connector
- Cable pulled from a molded connector
- Crimped joint separation
Suppose a crimped terminal separates from a wire at 185 N.
The useful result may simply be:
Maximum Pull-Out Force = 185 N
That is different from saying the wire material itself has a tensile strength corresponding to 185 N.
Which Standards Apply to Wire and Cable Tensile Testing?
There is no single standard that covers every wire, cable, terminal, insulation material, and connector tensile test.
The correct standard depends on the test object and product specification.
For cable laboratories, the following standards are particularly relevant.
IEC 60811-501 — Insulating and Sheathing Compounds
IEC 60811-501 is one of the most important references for mechanical property testing of non-metallic materials used in electric and optical fibre cables.
Its scope covers procedures for determining mechanical properties that typically apply to cross-linked and thermoplastic compounds used for insulation and sheathing materials.
This distinction matters.
IEC 60811-501 should not be presented as a universal pull test method for:
- A complete cable assembly
- A crimp terminal
- A USB connector
- A finished wire harness
Its focus is the insulating and sheathing compounds.
The current consolidated publication is:
ASTM D638 — Tensile Properties of Plastics
ASTM D638 covers tensile property testing of unreinforced and reinforced plastics using standardized specimens under defined conditions including pretreatment, temperature, humidity, and testing machine speed.
For wire and cable laboratories, ASTM D638 may be relevant when:
- Plastic cable materials are being characterized independently
- Plastic components require tensile property evaluation
- Material development or incoming-material testing is performed
It should not automatically replace a cable-specific specification.
If the final cable specification requires IEC 60811 or another product-specific method, that requirement takes precedence.
Current official page: ASTM D638-22
Related ITM-LAB article:
ASTM D638 Tensile Test for Plastic Materials | Complete Practical Guide
ASTM D412 — Rubber and Thermoplastic Elastomers
Cable products can contain highly flexible elastomeric materials.
ASTM D412 covers tensile testing procedures for vulcanized thermoset rubbers and thermoplastic elastomers. Its scope includes dumbbell/straight-section specimens and cut-ring specimens.
This standard can be relevant when evaluating elastomeric materials used in:
- Flexible cable components
- Protective jackets
- Seals
- Rubber-related cable assemblies
The current ASTM page lists:
ISO 37 — Vulcanized or Thermoplastic Rubber
ISO 37:2024 specifies a method for determining tensile stress-strain properties of vulcanized and thermoplastic rubbers.
Properties covered include tensile strength, elongation at break, stress at specified elongation, elongation at specified stress, and—in applicable materials—yield behavior.
Related ITM-LAB article:
ASTM D412 / ISO 37: Complete Guide for Tensile and Break Testing of Elastomers
Standards at a Glance
| Standard | Main Test Object | Relevant Result | Do Not Automatically Use It For |
| IEC 60811-501 | Cable insulation/sheathing compounds | Mechanical properties, tensile behavior | Finished connector pull test |
| ASTM D638 | Plastics | Tensile properties | Every finished cable test |
| ASTM D412 | Rubber/TPE | Tensile properties | Metal conductor testing |
| ISO 37 | Vulcanized / thermoplastic rubber | Stress-strain properties | Terminal retention test |
Practical Rule
Do not begin by asking:
“Which standard does this tensile tester comply with?”
A better sequence is:
Product specification → required test → specimen → measurement method → equipment configuration
A universal testing machine does not become “IEC compliant” or “ASTM compliant” simply because it can apply tensile force.
The complete test setup must meet the requirements of the applicable method.
How to Set Up a Wire or Cable Tensile Test
Once the test objective is clear, the equipment setup becomes much easier to define.
Step 1 — Define the Sample and Failure Objective
Start with the physical sample.
For example:
- 2 mm diameter wire
- 8 mm finished cable
- Cable jacket specimen
- Crimp terminal
- USB cable assembly
- Automotive wiring connector
Then ask:
Where should failure occur?
This question is often more useful than simply asking for the expected force.
If you are evaluating crimp quality, the terminal connection is the area of interest.
If you are evaluating conductor strength, a terminal pull-out before conductor failure may prevent you from measuring the property you originally intended to study.
Step 2 — Identify the Required Standard
Confirm whether the test follows:
- IEC
- ASTM
- ISO
- Automotive OEM specification
- Customer specification
- Internal QC procedure
Do this before setting speed, gauge length, specimen geometry, or conditioning.
A laboratory should not copy settings from an unrelated previous test simply because the samples look similar.
Step 3 — Estimate the Working Force Range
Machine capacity and measurement range are related, but they are not the same decision.
Consider a test expected to peak at approximately 80 N.
A 5 kN machine frame may have more than enough mechanical capacity.
That does not mean the laboratory should ignore the load-cell configuration.
If the system supports a lower-capacity load cell suitable for the actual working range, the same frame can still be a practical solution.
For this reason, tell the equipment supplier both:
Expected working force
and
Maximum possible force
rather than simply requesting the highest available machine capacity.
Step 4 — Select the Fixture
The fixture is often where a cable test succeeds or fails.
The machine may have enough force, enough travel, and suitable software—but if the cable slips before reaching the required force, the test setup still does not work.
Typical gripping solutions include:
- Flat tensile grips
- Wedge grips
- Pneumatic grips
- Roller or capstan-type grips
- Wire grips
- Cable grips
- Terminal fixtures
- Connector-specific fixtures
There is no single “best cable grip.”
The correct fixture depends on:
- Diameter
- Surface friction
- Flexibility
- Cross-sectional shape
- Expected force
- Failure mode
- Whether the sample can tolerate direct jaw pressure
Step 5 — Set the Test Parameters
Depending on the applicable method, parameters may include:
- Initial grip separation
- Gauge length
- Crosshead speed
- Preload
- Force limit
- Displacement limit
- Break detection
- Sampling rate
- Conditioning requirements
Particularly for polymeric and elastomeric materials, changing the test speed can affect the measured behavior.
That is why test speed should come from the applicable standard or procedure—not from a convenient machine default.
Why the Grip Can Matter More Than Machine Capacity
A common buying mistake is to focus almost entirely on:
500 N, 1 kN, 5 kN or 10 kN?
Force capacity matters, but it is only one part of the system.
Consider a cable expected to fail around 300 N.
A 1 kN machine has adequate force capacity.
But during the test, the cable begins slipping at 180 N.
The machine never reaches the actual failure point.
Changing the frame from 1 kN to 5 kN will not solve that problem.
The grip has to be reviewed.
Scenario A — Smooth Flexible Cable
A smooth jacket may gradually move between flat jaws.
Possible solutions may include:
- Different jaw surface
- Greater wrap length
- Roller/capstan-style gripping
- Increased gripping area
- Alternative fixture geometry
Simply increasing jaw pressure is not always the best answer because excessive pressure can damage the jacket.
Scenario B — Fine Wire
A small wire can be damaged by aggressive serrated jaws.
The sample may then fail at the jaw edge instead of in the intended test area.
The result looks like a wire strength failure, but the fixture may actually have created the weak point.
Scenario C — Terminal Pull Test
A terminal may have an irregular geometry that cannot be held reliably with ordinary tensile jaws.
A dedicated terminal fixture can hold the terminal while the wire is pulled along the intended axis.
The fixture should restrain the component without creating an unintended bending load.
What Should You Measure?
A useful test report should contain the measurements needed for the actual engineering decision.
Not every cable-related test requires every possible tensile result.
Maximum Force
Commonly useful for:
- Finished wire
- Cable
- Terminal
- Connector retention
Reported directly in:
N or kN
Tensile Strength
Used primarily for material characterization.
Tensile Strength = Maximum Tensile Force / Original Cross-Sectional Area
Commonly reported in:
MPa
Elongation at Break
For extensible materials:
Elongation at Break (%) = [(Final Gauge Length − Initial Gauge Length) / Initial Gauge Length] × 100
It can be particularly important when evaluating:
- Cable insulation
- Sheathing compounds
- Elastomers
- Flexible plastics
Force-Displacement Curve
A single number tells you how much force the sample reached.
The curve can tell you how it reached that point.
A force-displacement curve may reveal:
- Initial seating
- Gradual slip
- Stable deformation
- Yield-like behavior
- Sudden fracture
- Progressive pull-out
- Multiple structural events
For engineering development, this can be more informative than a simple Pass/Fail result.
Do Not Record Only the Peak Force — Record How the Sample Failed
Two specimens can both reach 185 N, but the result may not mean the same thing.
Consider:
Sample A
Wire breaks in the intended test section at 185 N.
Sample B
Terminal slips off the conductor at 185 N.
The peak force is identical.
The failure mode is not.
This matters in both R&D and quality control.
| Failure Mode | What It May Indicate |
| Wire breaks in intended test area | Wire/component strength reached |
| Insulation/sheath specimen ruptures normally | Material failure |
| Cable slips in grip | Fixture/setup problem |
| Terminal pulls out | Crimp or retention failure |
| Wire breaks directly beside terminal | Possible local stress concentration |
| Connector housing fractures | Connector structural failure |
| Sample repeatedly breaks at grip edge | Fixture, alignment, or specimen preparation should be reviewed |
A good test report should therefore include:
Peak value + failure location + failure mode
where relevant.
Common Testing Problems — What Should You Check First?
Problem 1 — Sample Slips Before Reaching Peak Force
Check:
- Grip type
- Jaw surface
- Wrap/contact length
- Sample geometry
- Clamping pressure
Do not immediately conclude that the machine lacks force capacity.
Problem 2 — Every Sample Breaks at the Grip
Check:
- Jaw edge geometry
- Excessive clamping pressure
- Alignment
- Specimen preparation
- Grip selection
If five samples all break at exactly the same jaw edge, that pattern deserves investigation.
Problem 3 — Test Results Vary Too Much
Before questioning the load cell, check basic test consistency:
- Same specimen dimensions?
- Same gauge length?
- Same conditioning?
- Same speed?
- Same operator setup?
- Same grip pressure?
- Same material batch?
- Same alignment?
Variability often comes from several small setup differences rather than one obvious equipment fault.
Problem 4 — The Force Signal Is Very Small Relative to System Capacity
Do not automatically replace the entire machine.
First determine whether a more appropriate lower-capacity load cell can be installed.
For laboratories testing:
- 30 N terminals
- 300 N cables
- 2 kN material specimens
using interchangeable load-cell ranges may be more practical than trying to optimize all measurements around one capacity.
Problem 5 — The “Wrong” Part Fails First
Suppose the goal is to test cable break strength, but the terminal pulls out first.
The test has still revealed something useful:
The terminal connection is currently the weaker point of the assembly.
However, it has not necessarily measured the intrinsic breaking strength of the cable.
That distinction should be documented.
How to Choose the Machine and Load Cell
Equipment selection becomes much easier when six questions are answered.
1. What Is the Sample?
Example:
- Fine electronic wire
- USB cable
- Automotive cable
- Finished power cable
- Cable jacket specimen
- Terminal
- Connector assembly
2. What Is the Expected Force?
If possible, provide both:
Normal test force
and
maximum expected force
A statement such as:
“Most samples fail between 60 and 90 N; maximum expected force is below 150 N.”
is much more useful to an equipment manufacturer than:
“We need a tensile tester.”
3. How Long Is the Sample?
This matters because test space has to accommodate:
fixture + specimen + expected extension
A highly extensible material may require more travel than expected from its original size.
4. What Has to Be Measured?
Choose from:
- Maximum force
- Tensile strength
- Elongation
- Crosshead displacement
- Strain
- Pull-out force
- Force-displacement curve
- Pass/Fail
The measurement requirement may influence whether an extensometer or other accessories are needed.
5. What Fixture Is Required?
If you do not know, send the supplier:
- Sample photograph
- Drawing
- Diameter
- Width
- Thickness
- Terminal geometry
- Connector geometry
For unusual cable assemblies, a fixture recommendation should be based on the real product, not on a generic catalog photo.
6. Laboratory or Production QC?
A laboratory performing five R&D tests per day may value fixture flexibility.
A production line performing hundreds of terminal pull checks may care more about:
- Loading speed
- Operator efficiency
- Quick clamping
- Pass/Fail judgment
- Repeatability
- Data traceability
The test objective can therefore influence more than just machine capacity.Three Practical Equipment Selection Examples
These are not customer case studies. They are example configurations showing how the selection logic works.
Example A — Small Crimp Terminal Pull Test
Sample: Crimped electronic wire terminal
Expected Force: Approximately 80 N
Required Result: Maximum pull-out force
Failure of Interest: Terminal separation
Test Frequency: Regular QC
A practical system may require:
- Low-force tensile tester
- Load cell appropriate for the expected working range
- Dedicated terminal holding fixture
- Wire gripping method
- Automatic peak-force recording
- Pass/Fail limits if used for production QC
For this type of low-force application, an RS-8010A Single Column Tensile Test Machine can be considered.
The key point is not simply that the machine can exceed 80 N.
The more important question is whether the selected load cell and terminal fixture are appropriate for the test.
Example B — Cable Jacket Material
Sample: Specimen prepared from cable sheath material
Objective: Material characterization
Results Required: Tensile strength + elongation at break
Applicable Standard: Determined from cable/material specification
The setup may require:
- Suitable tensile grips
- Correct specimen geometry
- Defined gauge length
- Controlled test speed
- Force measurement
- Appropriate elongation measurement
Here, treating the test as a simple “cable pull test” would be misleading.
The sample is actually being tested as a material specimen.
Example C — Larger Finished Cable
Sample: Finished cable
Expected Force: Several kilonewtons
Result: Maximum force / breaking force
Challenge: Preventing cable slip
A suitable configuration may require:
- Higher-capacity frame
- Correct load cell
- Cable-specific grip
- Sufficient travel
- Strong alignment
- Force-displacement recording
For higher-force applications, an RS-8000 Universal Testing Machine may offer a more suitable capacity range.
Again, the final decision should depend on the actual sample and fixture requirements.
RS-8010A vs RS-8000 for Wire and Cable Testing
For ITM-LAB's wire and cable applications, the two systems serve different force ranges and sample types.
| Selection Factor | RS-8010A | RS-8000 |
| Structure | Single-column | Universal test machine |
| Available capacity | 50 N–5 kN | 100 N–50 kN |
| Fine wire | Very suitable | Depends on configuration |
| Small terminal pull test | Very suitable | Usually unnecessary unless lab needs broader range |
| Small connectors | Very suitable | Application dependent |
| Insulation/sheath specimens | Suitable | Suitable |
| Medium-force cable tests | Capacity dependent | More suitable |
| Broader material testing | Moderate | Stronger flexibility |
| Higher-force applications | Limited to configuration | Up to 50 kN |
Consider RS-8010A When:
- The expected force is relatively low
- Samples are small
- Terminal and connector pull tests are common
- Multiple low-capacity load cell options are useful
- Laboratory space is limited
Consider RS-8000 When:
- Cable forces may reach several kilonewtons
- Larger specimens are tested
- The laboratory also performs compression, peel, shear, or bending tests
- A broader material testing platform is required
Machine suitability should always be confirmed using the actual sample, force range, fixture, test space, and applicable standard.
Before Requesting a Quote: Prepare These 7 Items
A detailed RFQ usually results in a much better equipment recommendation.
Instead of writing:
“Please quote one cable tensile tester.”
prepare the following information.
1. Sample Photograph
Include the complete sample and, if possible, a size reference.
2. Sample Dimensions
Provide relevant:
- Length
- Diameter
- Width
- Thickness
- Terminal size
- Connector dimensions
3. What Should Be Tested or Failed?
For example:
“We want to pull the terminal from the wire.”
or:
“We want to measure the tensile strength and elongation of the cable jacket.”
These two statements immediately lead to very different equipment configurations.
4. Expected Force
If known, provide:
- Normal force range
- Maximum force
- Existing test result
If unknown, provide the product specification.
5. Required Standard
Examples:
- IEC 60811
- ASTM
- ISO
- Customer specification
- Automotive OEM procedure
- Internal test method
If the requirement is an internal standard, sharing the relevant test-method section is often more useful than providing only the document number.
6. Required Results
Tell the supplier whether you need:
- Peak force
- Breaking force
- Tensile strength
- Elongation
- Pull-out force
- Force-displacement curve
- Stress-strain curve
- Pass/Fail
7. How Will the Machine Be Used?
For example:
R&D laboratory: 10 tests/day
or
Production QC: 300 tests/day
This can affect fixture design, operating efficiency, software requirements, and automation needs.
FAQ
What standard is used for cable tensile testing?
There is no single universal standard covering every cable-related tensile test.
For non-metallic cable insulation and sheathing compounds, IEC 60811-501 is an important reference. Finished cables, conductors, terminals, connectors, and wire harnesses may require other product-specific, industry, customer, or OEM procedures.
What does IEC 60811-501 test?
IEC 60811-501 provides procedures for determining mechanical properties of insulating and sheathing compounds used in electric and optical fibre cables. It typically applies to cross-linked and thermoplastic compounds.
Is cable pull force the same as tensile strength?
No.
Tensile strength is generally a material property expressed relative to the original specimen cross-sectional area.
Pull force is usually the direct force required to separate, break, or pull out a component or assembly.
Why does my cable keep breaking near the grip?
Possible causes include excessive clamping pressure, sharp grip edges, unsuitable grip geometry, stress concentration, specimen misalignment, or specimen preparation.
If failures consistently occur at the same grip location, review the setup before assuming the result represents normal sample strength.
What load cell should I use for a wire pull test?
Choose the load-cell configuration based on the expected working force and required measurement performance.
Do not select the load cell only from the maximum frame capacity.
For laboratories testing multiple force ranges, interchangeable load cells can provide greater flexibility.
Which machine is suitable for wire terminal pull testing?
For relatively low-force terminals, fine wire, and small connector assemblies, a single-column system such as the ITM-LAB RS-8010A can be considered.
The exact configuration depends on the expected force, terminal geometry, wire size, fixture, and required result.
Conclusion
The most important question in wire and cable tensile testing is not:
“How many kilonewtons do I need?”
It is:
“What exactly am I trying to make fail, and what result do I need from that failure?”
A cable jacket specimen, finished wire, crimp terminal, and connector assembly may all be tested on a tensile machine, but the useful test configuration can be completely different.
A better equipment-selection process is:
Sample → Failure Objective → Standard → Measurement → Fixture → Force Range → Machine
For low-force wires, terminals, connectors, and cable-material applications, the RS-8010A Single Column Tensile Test Machine offers configurations from 50 N to 5 kN.
For larger cables and broader material-testing requirements, the RS-8000 Universal Testing Machine extends the available capacity up to 50 kN.
Rather than selecting a machine from maximum force alone, send your supplier the sample, expected force, test standard, dimensions, failure objective, required result, and test frequency.
That usually leads to a much more useful testing system.
