Round Cutter

29 mm is the most commonly ordered diameter. It matches ASTM D395 Type 1 and ISO 815 Type A for compression set testing — the most widely performed round-specimen test in rubber QC labs. It is also suitable for hardness and density specimens.

ASTM D395 recommends using the die in a drill press or similar rotary device, rotating the cutting edge while pressing down with light force and soap lubrication. This minimises cupping of the cut edges. However, many labs use a hydraulic or pneumatic press for faster throughput — this works well for most rubber compounds. For very soft or tacky materials, the rotary drill press method gives cleaner edges.

After cutting, the specimen sits tightly inside the cylindrical die cavity. Without an ejector pin, operators may pry the specimen out with a tool, damaging the edges. For compression set testing, edge quality directly affects thickness measurement accuracy. The spring-loaded ejector pin pushes the disc out cleanly with no edge distortion.

If the diameter matches, the same cutter can be used for both materials. For example, a 29 mm cutter works for rubber compression set (ASTM D395) and can also cut paper discs for certain tests. However, paper is more abrasive on cutting edges than rubber, so dedicated cutters for each material type will maintain sharpness longer.

Yes. Finetech Engineering provides NABL-traceable dimensional certification for round cutters, verifying the internal diameter and cutting edge perpendicularity.

Yes. We manufacture round cutters to any diameter. Common custom sizes include 25 mm, 38 mm, 40 mm, and 50 mm. Contact us with your required diameter and standard.

Check the cut edges of your specimens under magnification. If you see cupping (specimen edges curling upward), burrs, or rough edges, the cutter needs re-sharpening. For compression set specimens, also check if your thickness measurements show increasing variability — this can indicate edge damage from a dull cutter. Finetech offers re-sharpening services.