The Surprising Problem With Measuring Anything

This video traces the evolution of probe-based metrology, from the granite cubit masters of ancient Egypt to touch trigger probes and the atomic force microscope. THE EMERGING NEED · Craftsmen filed each part to fit its neighbor, making every product a one-off. · Honoré Blanc's musket locks had to assemble from parts drawn at random. · Go and no-go gauges could fail a part, but never say by how much it missed. THE PLANE AND THE SCREW · Maudslay's "Lord Chancellor" bench micrometer resolved a ten-thousandth of an inch. · Whitworth's three-plate method produced true flatness with no existing reference. · His 1851 machine used a falling "feeling piece" to sense a millionth of an inch. THE MICROMETER · Palmer's 1848 handheld screw gauge read directly to five hundredths of a millimeter. · Brown & Sharpe's caliper amplified spindle travel roughly sixty to one. · Abbe's principle demanded the scale sit in line with the dimension being measured. GAUGE BLOCKS · Johansson's 1896 set of 102 blocks could build around 20,000 distinct sizes. · Lapped on a converted sewing machine, the blocks "wrung" together into a single solid bar. · Steel's thermal growth forced a reference temperature, fixed at 20C in 1931. THE COMPARATOR · Logan's 1883 dial indicator turned a few thousandths of plunger travel into a full sweep. · Zeroed on gauge blocks, it took accuracy from the blocks and sensitivity from the gears. · The frictionless LVDT turned displacement into a voltage, resolving hundredths of a micron. SURFACE TEXTURE · Identical bearing journals could run for years or seize within hours. · Abbott's stylus and the Talysurf magnified vertical motion up to 40,000 times. · Stylus roundness testing separated diameter from roundness, exposing three-lobed pins. THE COORDINATE MEASURING MACHINE · Ferranti's 1959 machine read probe position from moiré fringes on optical gratings. · DEA's three-axis bridge design set the layout still used today. · One arcsecond of carriage pitch shifts a probe tip 500mm away by 2.4 microns. TOUCH TRIGGER · Flexible Concorde fuel pipes deflected away from hand-pushed hard probes. · McMurtry's kinematic mount reseats on six contact points to a fraction of a micron. · Tripping at a tenth of a newton, it put measuring machines under full computer control. SCANNING AND ERROR MAPPING · Zeiss's flexure-suspended scanning probe collected thousands of points per second. · Every three-axis machine carries twenty-one geometric sources of error. · Hocken's error mapping meant a machine only had to be repeatable, not perfect. PROBING THE MATERIAL · Brinell measured hardness from the dent a steel ball left under a known load. · Sub-micron coatings needed dents too small to see with an optical microscope. · Instrumented indenters feel force and depth directly, refined by Oliver and Pharr in 1992. THE ATOMIC PROBE · Binnig and Rohrer's tunneling microscope was effectively one atom sharp. · The atomic force microscope touched with billionths of a newton, working on almost anything. · In 2019, the spacing of silicon's atomic planes became a way to realize the metre. ------ 19th CENTURY MEASURING TOOL PHOTOS BY The Science Museum Group https://www.sciencemuseumgroup.org.uk/ SUPPORT NEW MIND ON PATREON   / newmind   SOCIAL MEDIA Instagram - @newmindchannel #metrology #engineering #precisionengineering #measurement #manufacturing #machining #micrometer #gaugeblocks #CMM #coordinatemeasuringmachine #touchprobe #Renishaw #Zeiss #dialindicator #LVDT #surfacefinish #surfaceroughness #Abbeprinciple #Whitworth #Maudslay #interchangeableparts #qualitycontrol #inspection #nanoindentation #hardnesstesting #atomicforcemicroscope #AFM #scanningtunnelingmicroscope #STM #nanotechnology #engineeringhistory #industrialhistory #historyoftechnology #mechanicalengineering