Working Hours: 08:00AM – 06:00PM


Designed and Manufactured by CATRA The World’s Cutting Technology Organisation.

  • Quickly and accurately produces sharpness data
  • Uses standardised test procedures
  • Simple semi-automatic operation
  • Can be used for Quality Control, Research and Development and competitor product evaluation
  • Designed to evaluate a wide range of types and sizes of blades and pointed instruments
  • Self contained bench mounted unit
  • Does not damage the blade or knife edge

The sharpness testing of plain edges such as kitchen knives, professional knives, folding and sporting knives, razors, scalpel blades, utility blades, machine knives, industrial blades and even hand tools such as chisels can now be achieved with a small bench top instrument that uses a simpler system than that specified in ISO 8442.5. CATRA developed this machine to use cutting force measurement as a determination of edge sharpness. The test media is a specially calibrated silicon rubber produced exclusively for CATRA.

Accurate sharpness measurement of a blade edge is an essential part of knife quality control; this instrument gives you that knowledge

The ISO 8442.5 system for determining cutting performance and durability is not ideally suited to small blades and where a shear cut is required. The size of equipment and complexity of the ISO system makes simple sharpness only measurements time consuming and destructive. As result CATRA’s latest development follows on from the RAZOR EDGE DURABILITY and SHARPNESS (REDS) tester but without the blade wear system but with the ability to test larger blades.

The test utilises the constant cut depth method in which the blade is pushed normally, without longitudinal travel, into the test media. The cutting force is recorded as a measure of the sharpness, which means the lower the force the sharper the blade. The test media is either 8 mm square or with a 3 mm wide side bead silicon rubber which is bent around a 20 mm former and the cut is made into the outer periphery of this bend. This causes the rubber to open up the cut as the blade penetrates, thereby reducing the point of contact of rubber and blade to the tip of the edge only.

As the blade contacts the rubber the force increases to a maximum at which cutting starts to take place after which this cutting force falls to lower level. It is this maximum force that is used as the sharpness related figure. Although the above curve is not visually produced by the standard instrument the maximum cutting force is numerically recorded, however it is visible with the computer interface option.

For needles and other sharp pointed blades an optional alternative feed unit can be fitted using a polyurethane membrane as the test media, which is pulled taught, the point of the needle then penetrating through it. A similar force curve is generated and the instrument again displays this peak force as a measurement of sharpness. This test system has been proved by extensive trials to be able to accurately evaluate blade sharpening techniques and edge coatings, providing an essential tool for blade quality control and research and development such as heat treatments, sharpening and coating technology.

Machine description of CATRA Razor Edge Sharpness Tester (REST)

  • The equipment is suitable for bench mounting being built in its own stainless steel frame and is generally as shown in the photograph. The test media holder unit is static and manually loaded. The blade holder and slide are mounted on top of the frame with the motor drive system and controller underneath. The digital cutting force display and the motor controls are mounted on top of the frame.
  • The rubber test media is manually loaded around a self gripping former with quick action index mechanism, allowing the operator to accurately and repeatedly present a fresh surface towards the blade. Alternative test medias and holders are available for certain unusual blades or needle formats
  • The blade mounting unit consists of a flat plate which by a novel tilting mechanism can quickly align the blades, thereby enabling both flat and taper ground blades to be tested. On this plate are fitted moveable clamps to accommodate various blade cross sections or blade shapes, thereby giving accurate and repeatable blade positioning.
  • The blade unit is mounted to a linear low friction bearing slide, which is coupled to a high accuracy and resolution force measuring cell. The linear slide has have a stroke length of 1.5 mm and is be driven by a servo drive system, which is capable of speed adjustment, enabling speed calibration.
  • Within the control panel surface a digital display provides immediate readout of the peak cutting force in Newtons .
  • Optional computer interface for data logging within an Access database complete with graphical display. The access database allows report generation and test comparisons.
  • Optional blade holders for unusual blades/ instruments are available at additional cost.
  • Optional media carrier is available for membranes for needle and other sharp point testing.
  • Typically a sharpness measurement takes under 1 minute to perform and requires no special training of the operator.
  • The unit will carryout 200 sharpness test /metre of test rubber making consumable costs very low. CATRA carries large quantities of calibrated test media in stock.
  • Available in Voltages to suit all countries, Size 500mm x 590mm x 320mm weight 9.0 kg, allowing it to be relatively portable. A special carrying case can be provided as an option extra.
  • Typical sharpness levels :- Razor blade 0.3 to 0.4N, Scalpel blade 0.4 to 0.6N, Utility razor blade 1.0 to 1.4N, kitchen knife ( new) 1.8 to 3 N, Hunting knife 1.9 to 3.5, Well worn blade 6.0 to 11.0
  • Maximum blade width 100mm, maximum blade length 200mm.  Longer and wider blades can be accommodated with a special adaptor.

Note: This system is different to the ISO 8442.5 testing technique for sharpness measurement.  Hence, the results from this system are not directly comparable as the cutting performance of any specific blade or knife is dependant on the material being cut. For example a razor blade is great for shaving, but is useless at cutting down trees!

Machines available for rent for short term projects Or CATRA offers full independent and confidential testing services based on these machines.