Internal micrometers _ measurements are read in a similar way. They usually come with one measuring head and interchangeable ends so that a range of sizes can be measured. flexible steel tapes _ are read in a similar fashion as OD mics. Precision outside diameter These _ have a Vernier scale allowing measurements to within 0.001" accuracy. spindle _ measuring tapes are convenient substitutes for micrometers especially when measuring large diameters. For the 0"-1" mic shown here, a reading of 0.346" is arrived at by adding 0.300" plus the first. Sleeve markings are in 0.025" increments and thimble markings are in 0.001" increments. At that point, the size can be read from the markings on the sleeve and thimble. Micrometers A part to be measured is placed between the _ and anvil and the thimble is rotated until they all touch. ![]() Larger sizes are usually of interchangeable-anvil type with one frame (for a 6" to 12" set, for example). For inch sizes, they are available usually as individual micrometers (or "mikes") for each one-inch range up to 6" (0"-1", 1"-2" and so forth). A micrometer for external measuring is shown here. Some scales have graduated marks along the end for measuring short distances in locations otherwise inaccessible coiled scales, or tape measures, _ are measuring instruments constructed with screw threads of extreme accuracy. ![]() Common scale lengths are, 6", 12", 18", and 24" scales Of course, _ are also available but are not as precise as steel rules. A typical inch scale will have graduation increments of 1/64" and of 1/32" on each of the two edges of one side and 1/16" and 1/8" graduations on the edges of the other side. Rules, or scales, For use in manufacturing environments, _ are usually made of steel and can be either rigid or flexible. Often, sets of different graduations are placed along other edges of the same scale. They have marks accurately engraved at graduated intervals along the length of the scale. Both manual and electronic versions are available, and the electronic versions often have the capability to switch back and forth between inch and metric units Measuring instruments _ are the most basic tools for linear measurements. They are designed to measure either inch or metric units. ![]() Shown here is a tolerance for perpendicularity between two surface Geometric tolerances _- are precision tools available from many sources worldwide. Standard symbols are used to denote geometric tolerances on drawings. Tolerance limit _ are used when certain geometric conditions must be closely maintained on a feature or between features, like flatness, concentricity, parallelism, etc. of a cylinder, it should be shown as Ø2.749"/2.751". If the dimension in this example were applied to the I.D. When using this method, the first value should be the limit first arrived at when machining. In this case, only the maximum and minimum values allowed for the dimension are shown, stacked vertically, instead of including any separate tolerance values. The target size is 0.500" and a part measuring anywhere between 0.499" and 0.500" would pass inspection, but notice that the tolerance is unilateral since deviation is allowed only in the negative direction in this cas Unilateral tolerances _ notation is an alternative method of showing the tolerance range of a dimension.
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