Using the Vernier Calipers & Micrometer Screw Gauge | Department of Physics
A micrometer sometimes known as a micrometer screw gauge, is a device incorporating a .. to affix a label to each gauge that gives it an ID number and a calibration expiration date, to keep Loo Kang, Wee; Hwee Tiang, Ning (), " Vernier caliper and micrometer computer models using Easy Java Simulation and its. AboutAn open source physics at Singapore simulation based on codes written by Fu-Kwun Hwang, of a screw to amplify small distances that are too small to measure directly into large rotations of the Screw (not seen) The heart of the micrometer It is inside the barrel. . Release Date, October 06, Virtual micrometer in millimeter hundredths - simulator of use, reading and click in the eye to hide the result of the measure in mm; to reduce the number of.
This references the fact that the usual name for the device in German is Messschraube, literally "measuring screw". Spindle The shiny cylindrical component that the thimble causes to move toward the anvil. Thimble The component that one's thumb turns. Ratchet stop not shown in illustration Device on end of handle that limits applied pressure by slipping at a calibrated torque. The spindle of a micrometer graduated for the Imperial and US customary measurement systems has 40 threads per inch, so that one turn moves the spindle axially 0.
The 25 graduations on the thimble allow the 0. Thus, the reading is given by the number of whole divisions that are visible on the scale of the sleeve, multiplied by 25 the number of thousandths of an inch that each division representsplus the number of that division on the thimble which coincides with the axial zero line on the sleeve. The result will be the diameter expressed in thousandths of an inch. As the numbers 1, 2, 3, etc.
Suppose the thimble were screwed out so that graduation 2, and three additional sub-divisions, were visible on the sleeve as shown in the imageand that graduation 1 on the thimble coincided with the axial line on the sleeve.
The reading would then be 0. Metric system[ edit ] Micrometer thimble with a reading of 5.
The spindle of an ordinary metric micrometer has 2 threads per millimetre, and thus one complete revolution moves the spindle through a distance of 0. The longitudinal line on the sleeve is graduated with 1 millimetre divisions and 0. The thimble has 50 graduations, each being 0.
Using the Vernier Calipers & Micrometer Screw Gauge
Thus, the reading is given by the number of millimetre divisions visible on the scale of the sleeve plus the particular division on the thimble which coincides with the axial line on the sleeve. Suppose that the thimble were screwed out so that graduation 5, and one additional 0. The reading then would be 5. Vernier micrometers[ edit ] Vernier micrometer reading 5.
Some micrometers are provided with a vernier scale on the sleeve in addition to the regular graduations. These permit measurements within 0.
The additional digit of these micrometers is obtained by finding the line on the sleeve vernier scale which exactly coincides with one on the thimble.
The number of this coinciding vernier line represents the additional digit. Thus, the reading for metric micrometers of this type is the number of whole millimeters if any and the number of hundredths of a millimeter, as with an ordinary micrometer, and the number of thousandths of a millimeter given by the coinciding vernier line on the sleeve vernier scale.
For example, a measurement of 5. The vernier would then be used to read the 0. Inch micrometers are read in a similar fashion. Therefore, metric micrometers provide smaller measuring increments than comparable inch unit micrometers—the smallest graduation of an ordinary inch reading micrometer is 0.
When using either a metric or inch micrometer, without a vernier, smaller readings than those graduated may of course be obtained by visual interpolation between graduations.
Torque repeatability via torque-limiting ratchets or sleeves[ edit ] This section possibly contains original research. Please improve it by verifying the claims made and adding inline citations. Statements consisting only of original research should be removed. September Learn how and when to remove this template message A micrometer reading is not accurate if the thimble is over- or under- torqued.
A useful feature of many micrometers is the inclusion of a torque-limiting device on the thimble—either a spring-loaded ratchet or a friction sleeve. Without this device, workers may overtighten the micrometer on the work, causing the mechanical advantage of the screw to tighten the screw threads or squeeze the material, giving an inaccurate measurement. However, with a thimble that will ratchet or friction slip at a certain torque, the micrometer will not continue to advance once sufficient resistance is encountered.
This results in greater accuracy and repeatability of measurements—most especially for low-skilled or semi-skilled workers, who may not have developed the light, consistent touch of a skilled user. It might seem that there would be no such thing as too little torque on the thimble, because if zero tightening of the threads is the goal, then the less torque, the better. However, there is a practical limit on this ideal.
Some tiny amount of torque, although very slight, is involved in the normal hand movements of well-practiced micrometer use. It is light but not truly zero, because zero is impractical for a skillful feel of how the contact is being made. And the calibration reflects this amount, as tiny as it is.
If one then changes to an "afraid to even touch it" sort of gingerlinessone is being inconsistent with the norm that the calibration reflects, resulting in a reading that is 1 to 3 tenths too big on a typical metal part.
Related to this torque topic is interuser variation in what is normal. It is important to try not to have an idiosyncratic touch, because although it works perfectly well for intrauser consistency, it interferes with interuser consistency.
Some people use a rather heavy touch as a matter of habit, and this is fine in that they can get highly accurate readings as long as they calibrate their micrometer accordingly. The problem arises when they use someone else's micrometer, or when someone uses theirs. The heavy-touch user gets false-small readings, and the normal-touch user gets false-big readings. This may not arise in one-person shops, but teams of workers sharing company-owned instruments must be capable of interpersonal consistency to do close-tolerance work successfully.
There is a good and easy way to synchronize on this topic: This is proper training for the machining trade, although it is not uncommon to encounter coworkers who were not well trained on this point.
In many cases it seems that in drilling the "don't overtorque" idea into trainees' heads, an opposite extreme is mistakenly taught, where the user thinks the goal is to compete with everyone else on who can generate the lightest touch. Individuals naturally differ in their touch, so such a competition is not as effective at generating interuser consistency as is "imagining that every thimble has a sleeve to slip.
Virtual Micrometer in Hundredths Millimeter - Simulator | Prof. Eduardo J. Stefanelli
There is usually a small hole in the sleeve to accept the spanner's pin. This calibration procedure will cancel a zero error: Testing[ edit ] A standard one-inch micrometer has readout divisions of. Both the measuring instrument and the object being measured should be at room temperature for an accurate measurement; dirt, abuse, and low operator skill are the main sources of error.
If the gauge block is known to be 0. If the micrometer measures 0. Cleanliness and low but consistent torque are especially important when calibrating—each tenth that is, ten-thousandth of an inchor hundredth of a millimeter, "counts"; each is important. A mere spec of dirt, or a mere bit too much squeeze, obscure the truth of whether the instrument is able to read correctly.
Calibration typically checks the error at 3 to 5 points along the range. Only one can be adjusted to zero. If the micrometer is in good condition, then they are all so near to zero that the instrument seems to read essentially "-on" all along its range; no noticeable error is seen at any locale. In contrast, on a worn-out micrometer or one that was poorly made to begin withone can "chase the error up and down the range", that is, move it up or down to any of various locales along the range, by adjusting the sleeve, but one cannot eliminate it from all locales at once.
Calibration can also include the condition of the tips flat and parallelany ratchet, and linearity of the scale. The reading here is This Java applet will help you to understand how to read a vernier scale.
The vernier calipers The vernier calipers found in the laboratory incorporates a main scale and a sliding vernier scale which allows readings to the nearest 0. This instrument may be used to measure outer dimensions of objects using the main jawsinside dimensions using the smaller jaws at the topand depths using the stem. The vernier calipers To measure outer dimensions of an object, the object is placed between the jaws, which are then moved together until they secure the object. The screw clamp may then be tightened to ensure that the reading does not change while the scale is being read.Video 4: How to use Micrometer Screw Gauge?
Watch this short movie to see how to do this. The first significant figures are read immediately to the left of the zero of the vernier scale and the remaining digits are taken as the vernier scale division that lines up with any main scale division.
Note that the important region of the vernier scale is enlarged in the upper right hand corner of each figure. The reading is In figure 4 above, the first significant figures are taken as the main scale reading to the left of the vernier zero, i. The remaining two digits are taken from the vernier scale reading that lines up with any main scale reading, i.