Evaluating the sizes of Lightspeed instruments

The diameters of six different sized Lightspeed cutting heads were measured using a modified optical micrometer. Six specimens of instrument sizes 20, 22.5, 27.7, 30, 32.5 and 45 were examined. Except for one cutting head of size 30, all the recorded diameters were oversized compared to the expected diameter and the permitted tolerance (+/- 0.005 mm). Perfectly machined instruments would increase by 12.5%, 9.09% and 8.3% from instrument sizes 20-22.5, 27.5-30 and 30-32.5, respectively. Under the conditions of this study, the corresponding increases were 7.1%, 6.75% and 8.54%. Instrument size 20 had the widest range and is the smallest instrument in the Lightspeed set. The largest differences between the recorded and expected means were registered for the size 45 group. An earlier study using a different measuring method reported that Lightspeed instruments were mostly undersized.