ASNT Level III- Visual & Optical Testing
My Level III Self Study Notes Reading 4 Section 4B
My Level III Self Study Notes Reading 4 Section 4B
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7.2.3 Grinding and Polishing<br />
Fine grinding and polishing are needed for visual tests of<br />
small structural details, welds and the effects of heat treatment.<br />
Finer grinding usually is done with 80 to 150 abrasive<br />
grit followed by 150 to 180 grit and finally 400 grit (an American<br />
indication of grit size, 400 being the finest). At each<br />
stage, marks from previous grinding must be completely removed. Changing<br />
the grinding direction between successive<br />
stages of the process aids the visibility of previous<br />
coarser grinding marks. Coolant is required for grinding and<br />
typical abrasives include emery, silicon carbide, aluminum<br />
oxide and diamond.<br />
Charlie Chong/ Fion Zhang