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For Accurate Notched Specimens

The test specimen is the most important component of testing, for it determines the actual physical properties of the material being tested. The specimen must conform to exacting physical dimensions and must be free of induced heat distortion. Qualified laboratory personnel and accurately calibrated testing machines are important, but the ultimate test results are based on the quality and accuracy of the test specimen.

Developed in response to a growing need for Iosipescu Shear Test specimens, the V-Mill I, powered by 26,000 RPM motor, was developed specifically for the rapid and accurate machining of v notch shear specimens from composites and other non-metallic materials. Precision test specimens can be finished rapidly, with excellent results, by operators without previous machining experience. Specimen configurations are in accordance with ASTM standards for V notch shear testing.

The test strip must be pre-cut to the correct length and width, using the Tensilsaw or Tensilkut machine, and is then clamped in a precision template which is manually moved across the V-Mill table during the machining of the notches into the test specimen. The template rides along the guide plate, which is manually adjusted by a micrometer control knob, similar to those found on Tensilkut machines. A series of passes ensures that both notches are cut evenly and symmetrically; the micrometer control will reach a stop when the notches are the correct depth. Due to the high cutting speed of the motor, only light hand force is required to accurately notch the specimen.

Optional V-Mill Subsystems

The Motor Speed Control is an electronic control designed specifically for use with the Tensilkut high speed motors. It permits infinite variations of motor speed from 10% to full speed with minimal loss of power. The motor speed control is ideal for use with materials having a low melting point, for the reduction of motor speed correspondingly reduces the heat generated by the cutter. It is suggested that the motor speed control be ordered with the V-Mill, although it can be retrofitted at a later date.

The Tensilmist system is used to reduce the amount of dust generated during the preparation of notched specimens from certain materials such as fiberglass and Kevlar. This is achieved by spraying a fine mist of water on the cutter and sample during the cutting operation. A one quart reservoir can be filled with water, which is sprayed through the neoprene and brass hose and nozzle built into the V-Mill, if it is ordered. A minimum of 50PSI air line is required for the Tensilmist, and it must be ordered with the machine.

The Tensilvac is ideal for removal of much of the dust generated during the notching process. The Tensilvac system includes a wet/dry vacuum canister and the necessary slots machined in the control head and table of the V-Mill machine to enable dust and chip removal during the cutting process. Tensilvac must be ordered with the V-Mill when it is built.

V-Mill Templates

The Master Templates for the V-Mill are available for both of the current Shear Test methods. These moderately priced templates are designed to hold one or more samples for fast and easy notching of the prepared blanks.

To prepare a Shear Test specimen, a strip must be precut to its overall dimensions using the Tensilsaw or Tensilkut. One or more strips are inserted into the template between the stationary bar and the clamping bar, which is then tightened using the allen wrench supplied to hold the specimen in position, and not removed from the template until both sides of the specimen are completely machined. This reduces errors caused by reversing samples, ensuring that the notches on both side are perfectly aligned.

V-Mill Cutters

The 80-11 Cutter for the V-Mill is a custom designed, diamond coated cutter made specifically for preparing accurate notches in Shear Test specimens. These cutters are designed for maximum surface finish and notch configuration on the test specimens prepared with the high speed V-Mill. Replacements are available from Tensilkut Engineering.