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Your supplier of high pressure laboratory instruments

CAI-70 West Cerchar abrasivity index tester

ASTM D7625-10


The CAI-70 accurately determines the rock abrasivity index (CAI) employed for the classification of rock materials in terms of abrasivity. The CAI is a dimensionless unit obtained from measuring the wear on a HRC55 Rockwell Hardness steel stylus tip after it has been used to abrade a specimen with a 70N normal force. The apparatus comprises a stationary stylus, a deadweight (70N) placed on top of the stylus, a stiff load frame, a rigid vice to firmly clamp the rock sample and a cross table with 2 adjustable axes for specimen alignment along the two horizontal axes. The device comes with a graduated knob for 0.01 mm accurate scratch distance control. Options include an indenter visualization system, spare indenters and a sharpening tool. The former encompasses a digital camera with indenter support and inspection software to reveal the wear amount which is then correlated to the abrasiveness index (CAI). The sharpening tool rapidly sharpens 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)

330 x 500 x 500 mm


ASTM-compliant, West model

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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