Your supplier of high pressure laboratory instruments

Your supplier of high pressure laboratory instruments

OCAI-70 Original Cerchar abrasivity index tester

ASTM D7625-10


The OCAI-70 is a precise tool used to determine the rock abrasivity index (CAI), which plays a vital role in classifying rock materials based on their abrasiveness. This CAI is a dimensionless measurement derived from assessing the wear on a HRC55 Rockwell Hardness steel stylus tip after it has been used to abrade a specimen subjected to a 70N normal force. The instrument follows the ASTM D7625 method for assessing rock abrasiveness. The apparatus includes a mobile stylus and a deadweight (70N) positioned above the stylus. An articulated axis allows the user to place the stylus on the fixed specimen, and then, by moving the axis, creates a consistent 10mm-long stripe. The operator manually moves the stylus at a speed of 1mm/second during the test. Optional features encompass an indenter visualization system, spare indenters, and a sharpening tool. The indenter visualization system consists of a digital camera with support for the indenter and specialized inspection software. This system reveals the extent of wear on the stylus, which is then correlated to determine the abrasiveness index (CAI). The sharpening tool is utilized to quickly restore a worn stylus for subsequent scratch tests.



ASTM D7625-10.


70 N

Maximum specimen height           

150 mm (6 inches)

Maximum specimen diameter

76 mm (3.0 inches)

Scratch distance precision

0.01 mm

Steel Stylus

Rockwell Hardness HRC 54/56


25 kg

Dimensions (WxLxH)

260 x 460 x 375 mm


ASTM-compliant, original version

Easy manual handling

Features precision slide for smooth movement of the rock specimen over the required scratch distance

Easy adjustment of the daylight for different specimen heights

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