At Quality Bar the finish of a TGP bar is measured in RMS. It can be detected by both the naked eye and by touch. An experience grinder operators, can visually estimate the RMS finish. RMS or Root Mean Square, is a form of measuring the difference between the peaks and valleys on the surface of the TGP bar. A bar with a lower RMS reading has a better finish than one with a higher RMS reading. The less the distance between the peaks and the valleys, the smoother and more "mirror like" the finish and/or the lower the RMS reading. Quality Bar uses a hand held digital tester called a profilometer to measure RMS.
A TG&P bar receives its final finish in the grinder. The straighter the bar is going in the grinder, the better the finish coming out. We have discussed how the straightness of the bar entering the grinder is a function of the work performed at the # 2 straightener. The turning machine also affects the finish. The smoother the barber poles, the more likely the bar will have a better finish.
The grit on the grinding wheel surface is a major factor in the finish of a TGP bar. If one uses a lower grit wheel, one grinds less per pass and gets a better finish. If one uses a larger grit wheel, one gets a greater reduction but a rougher finish. Lower grit wheels require more passes at a higher cost.
To produce a commodity bar companies tend to use lower grit to increase their capacity and reduce their cost. At Quality Bar we prefer a higher grit wheel which gives a better finish, but at a higher production cost.