through such precision instruments as these our standards of accuracy are being changed science has opened the gateway to new conquests in accuracy of measurement the yardstick has expanded until hundreds of an inch thousands of an inch even millions have become measurable quantities and the power of man's senses has been extended to reach into a new world that he cannot comparison have grown infinitely small chemists and engineers the scientists of industry are becoming more and more familiar with the fantastic land beyond the microscope through lenses which magnify hundreds and thousands of times metal experts count and even measure the crystal structures which make up iron and steel a measuring stick smaller than a pinhe lines of thousands of an inch apart under the searching lens of the microscope small blocks of metal in the laboratory tell the secrets of the millions of tons of iron and steel that go into the huge manufacturing plants and in these plants microscopic precision controls the form and size and surface of every part through the development for factory use of all these precision devices for the measurement of things infinitely small within limits of tolerance that are almost absolute we are now able to meet the precision demands of quantity production of find parts on the basis of standardization and complete interchange ability is dropped on the surface being tested the amount of bounce measured the hardness of the surface hard metals are also tested in a large master gave the metal is placed on a support and a diamond point is forced into the surface the distance the point penetrates is measured accurately on a dial to determine the exact degree of hardness a similar type of master gauge is used for checking the toughness of metals in this method a steel ball under great pressure is forced into the surface of the metal the dent or hollow formed in the test specimen is measured under the microscope master instruments check the accuracy of measurements within half a hundred thousandth of an inch master gauges check the accuracy of tools and parts used in the factories and on the assembly lines the size of the parts is so accurately controlled that if the piston is chilled for a moment on ice it will contract and the pins when warmed will expand so that the two will no longer fit under all ordinary conditions the two parts will fit perfectly but if we reverse the operation and warm the piston it will expand again and the pin chilled on ice will contract and now it's too loosely in the hole limits of accuracy and inspection of piston pins are so small that they are almost beyond comparison finished pins fit smoothly into the pistons with no difference in size over one tenth of a thousandth of an inch surfaces of moving parts are checked with in extremis  measurements that are invisible to the human eye sensitive electric meters and delicate feeler points check piston diameters in terms of a single inch divided into ten thousand part cylinders are checked for equal perfection in diameter roundness and smoothness precision cutting machine shape and round the cylinders there's asian polishing machines politian grind the walls to smoothness and precision gauges guide the inspection of the finished work the pistons move up and down in the cylinders of the automobile engine with just enough room to spare for a film of oil thinner than the walls of a soap bubble in the careful assembly and fitting together of the parts many different types of gauges are needed in the factory a gauge known as an amplifying indicator is used as a precision check on the fit of the main bearings a delicate feel or arm which travels over the surface of the bearing is connected so that it slightest movement show it on a  thousandth of an inch the tools called go and no go gauges automatically guard the perfection of every part the upmost precision is carried directly into every step of manufacture the openings between the two prongs of this gauge have been set according to exact measurements of valve stem that will not go through the top opening is rejected because it is too large a valve stem that will go through both openings is also rejected because it is too small a perfect valve the stem will go through the top opening and will not go through the bottom opening yet the difference is less than the thickness of a hair inspection of automobile parts in the factory requires the use of many different sizes and shapes of gauges special gauges are used to measure the of transmission gears slight imperfections are magnified so that only perfect gears may find their way into the finished product the dials detect the factories to make sure that gears  throughout the great manufacturing plants tools instruments gauges work with almost uncanny intelligence sorting and selecting jackie passing all rejecting ever on guard for the slightest research can provide in the way of measurements that are precisely so