Tests to Determine Machinability Index

Tests to Determine Machinability Index

Tests to Determine Machinability Index - They are:

1. Long-Time tests

2. Short-Time tests

(1) Long-Time wear test determines machinability based on cutting speed. The test finds out the tool life cutting speed relationships for the test material and for a reference material under identical conditions of testing. Though this test is very reliable, it consumes considerable time and material.

(2) Short-Time tests are not so reliable but take much less time and material. They can be advantageously used for comparing different materials as regards their machinability.

Short time tests may be classified as follows:

(a) Tests at elevated cutting speed, when conducted effect rapid tool wear.

They are used for the rapid comparison of different materials for their machinability rating.

(b) Facing tests are carried out from the centre of the workpiece towards its periphery. The diameter at which the tool fails is the measure of its machinability.

(c) Workpiece is machined using radio activated cutting tool. The chips thus produced carry some amount of radioactivity from the cutting tool proportional to the wear developed on the tool. Radioactivity of a known quantity of chips is measured with a suitable counter to assess the machinability of the workpiece material

(d) Tests with low wear criterion have the same basic procedure as those of longtime tests, except that low values of wear are taken as the criterion for machinability assessment, in order to reduce the time and material requirements for the tests.