Tensile Test Sample Specimen Punch - Punching Press Advantages

Tensile specimens are punched using a slow cutting action. Unlike an eccentric punch, this method limits edge damage and work hardening to just 10% of the sheet thickness per side—provided the sheet thickness range is properly configured. An eccentric punch should not be used for these tasks.

With impact punching, work hardening and damage can reach up to 35% of the sheet thickness, making it impossible for the Specimen Grinding Machine QualiPSM2000-15 to fully correct. However, the newly developed Specimen Grinding Machine QualiPSM2000-15-A, a fully automatic sample grinding machine with active cooling introduced in 2022, now makes this possible. Its advanced design prevents heat buildup, ensuring precise, damage-free grinding even during extended use.

Key Features of Our System

• From coil to tensile test in under 3 minutes
• Easy operation – Can be used by anyone, even while a tensile test is in progress
• Top-tier sample quality – Achieved with the world’s only Specimen Grinding Machine QualiPSM2000-15
  • Essential for R+N value testing
  • Indispensable for hardened sheet metal (press hardening / hot forming)
• Unmatched expertise – Hundreds of punches, tools, and grinding machines worldwide
• Trusted by industry leaders – Customers say: "Your client list is like the 'Who’s Who' of the sheet metal industry."

Tensile Test Sample Specimen Punch - Punching Press

Tensile Test Sample Specimen Punch – Punching Press hydraulic specimen punches have been a top choice in testing technology for years. Since 1970, we have been designing and supplying punches, punching tools, and the exclusive Specimen Grinding Machine QualiPSM2000-15. As the original inventor, we remain the world's sole provider of this specialized grinding machine, essential for eliminating the punching edge and work-hardened zone in the gauge length—ensuring precision from radius to radius.

• Compatible with a single punching tool
• Supports interchangeable molds with one or two parking tables
• Multi-zone punching for robotic systems:
  TWIN / TRIPLE / QUAD configurations with 2, 3, or 4 cylinders/work areas

Our punches are specifically designed to meet the demands of testing technology in the sheet metal industry. While they are standard products, they can be tailored to your exact requirements. Their straightforward design makes them single-purpose tools, ensuring they are used exclusively for testing, not other tasks. This streamlined approach allows for a cost-effective machine design, often making our presses more affordable than even second-hand punches from the machine tool trade. Additionally, they are not suited for production tasks, keeping them dedicated to your test lab.

Tensile specimens are punched using a slow cutting process. Unlike an eccentric punch, this method limits edge damage and work hardening to just 10% of the sheet thickness per side—provided the sheet thickness range is properly designed.

Avoid using an eccentric punch for these tasks. Abrupt punching can cause work hardening and damage up to 35% of the sheet thickness.

New: The fully automatic Specimen Grinding Machine QualiPSM2000-15-A, developed in 2022 with active cooling, now allows thick samples (up to 12 mm) to be ground without excessive heating (<50°C). However, this requires the samples to remain straight during punching, which is ensured when using our specialized punching tools.

The punching tool is mounted on the punching table. In the upper section, the T-slot insert and holder are visible, allowing for a standard tool change in under 10 seconds.

General Information on Preparing Tensile Specimens from Sheet Metal

Punching is the most cost-effective method for producing tensile specimens from sheet metal. However, performing a tensile test on a specimen that has only been punched is generally ineffective and does not meet industry standards. Even with the best tensile testing machine, results will be inaccurate if the damaged punched edge—hardened due to edge compression—is not properly removed through grinding or milling.

According to ISO 6892 (ASTM, JIS):
"The production of these specimens by punching can lead to significant changes in material properties, especially yield and strain limits. Materials that undergo substantial hardening should always be finished by milling or grinding."

Soft metals are particularly prone to deformation (edge rounding), which can increase the Rp0.2 value by up to 20%. Additionally, elongation measurements for punched-only samples are typically 25% to 50% lower, as work hardening causes microcracks that lead to premature failure—especially in high-strength sheets over 700 MPa.

Press Hardening / Mold Hardening

Customers frequently report that certain steels, such as 22MnB5 Manganese-Boron steel, are nearly impossible to mill. Due to their extreme toughness, milling cutters become blunt almost immediately, further compressing and hardening the material instead of removing it. The only effective solution for finishing these ultra-tough sheets is with the Specimen Grinding Machine QualiPSM2000-15 or the Specimen Grinding Machine QualiPSM2000-15-A, an advanced automatic version with cooling.

Punching Hardened Sheet Metal with Extreme Tensile Strength

Punching relies on the principle that the punch must be significantly harder than the material being cut. Our punches and cutting plates (dies) have a hardness of 60–62 HRC (~2,260–2,335 MPa).

However, as sheet metal hardness increases, the sharpness of the punch and die wears down exponentially faster. For materials above 1,800 MPa, we generally do not recommend punching—except for extremely thin sheets (up to 0.3 mm).

Maximum Punchable Strength

• Up to 1,200 MPa → Standard tools
• >1,200–1,800 MPa → Special tools made of high-alloy punching steel with PVD coating
• Stainless steels & soft deep-drawing sheets → Require twice the number of punching tools to minimize burr formation and edge deformation (grinding is mandatory) due to their high toughness and elongation.

Formula for Punching Force Calculation

Circumference x sheet thickness x tensile strength Rm x shear value 0.8 x factor shear angle 0.6 - 0.8 (tool shear angle slope)
Unit Conversions:

• Newton (N) → Kilonewton (kN) → Divisor by 1,000
• Newton (N) → Tonnes of Punching Force → Divisor by 9,810

Punching Tool Grading

For optimal testing accuracy and extended tool life (cutting sharpness until next regrinding), it is not advisable to use a single punching tool for all sheet thicknesses.

Large cutting gaps lead to excessive burr formation as the punching edge is pulled into the gap.

While burrs are less of a concern, soft sheet metal (<500 MPa) experiences extreme compaction at the edge due to punching force, creating a work-hardened zone.

This hardened edge must be removed through grinding, which also eliminates any burrs.

If the hardened zone is too deep, excessive grinding is required, increasing processing time and potentially causing excessive heat buildup in the sample.

Solution: The Specimen Grinding Machine QualiPSM2000-15-A sample grinding machine, with integrated active cooling, ensures efficient material removal without overheating, making it the only viable option for such cases.

Please note: 

All national and international standards require the removal of edge compaction caused by punching. This is essential because:

• Edge compression leads to work hardening, especially in soft materials rather than hard materials.
• Yield strength (Rp0.2) results can be off by up to 20%, significantly affecting accuracy.
• Elongation can decrease by up to 1/3, impacting material performance analysis.

To meet standards and ensure reliable results, specimens must be processed using a specimen grinding machine or, alternatively, milled.

Sample Mould for Punching Tools & Sample Grinding Machine

To effectively remove work hardening with a sample grinding machine (or by milling), the punching process must include an oversize allowance (b+).

• The required oversize depends on sheet thickness.
• Even if testing only punched specimens, it is essential to ensure the punching tool includes an oversize (e.g., max. 20.9 mm).
• This provides enough material for milling or grinding, ensuring compliance with testing standards.

TWIN - Double punching machine two working areas

Dismantled punching tool for tensile tests on lateral roller table Option: Parking space for interchangeable tools)

Subject to technical changes - in the interest of improvement Other models and capacities available, please contact us

Special press for hard cutting hardened sheet metal: mould hardening / press hardening / hot forming
This press with automatic mode for simulating mould hardening / press hardening / hot forming

New: ZS5000 TITAN pressing force 500 tonnes for 500 mm long samples

New design and new paintwork ZS650CN with only 1 tool table