Linguistic glob

Is the Actual Mating Envelope and Datum mean the same thing for this Feature of Size (10 mm Pin) ? No. they are different concepts. The datum is a theoretical surface (perfect points, lines, and planes). Measurements cannot be made from theoretical surfaces. It is the perfect cylinder of the pin, theoretical. The purpose of datumes is for the location and orientation of features, it is the origin from which the location or geometric characteristics of features of a part are established The mating envelope of the 10 mm pin, that happened to be also a datum, is not a theoretical surface. The diameter of this perfect cylinder can get bigger or smaller as required, and more ever is not the size of the pin but the size of the smallest hole in which the actual pin size goes in. So, it is an actual size, not a theoretical one. The actual mating envelope of a pin is the smallest similar hole counterpart that fits over the pin and contacts the pin at the highest points.  The...

What’s the “CMM runout error”? When you measure the runout on CMM, the CMM induces a lot of error into the measurements. If you have 2 axes in your CMM program for the runout, for example, the axis of a feature, a circle, and the axis of the datum -A-, a cylinder, each axis of movement during the measurement is going to add an element of error. The axis of the features and datum -A- always are off to the axes of CMM. That “off” is a very little angle, A1/A2 angles, but that “little angle” end up magnifying error substantially when , for example, it is about a .0005 tolerance. You can simply see it if you examine the difference in the A1/A2 angles between the features. You cannot change the A1/A2 angles on CMM. On a Roundness tester you make A1/A2= zero before measuring the runout. A roundness tester allow us to correct the A1/A2 angles, to center the part axis on the spindle so that the runout will be in the part in which the axis feature-datum have 0° angles to the axes of the mac...

The mosaic represents  the twins Romulus and Remus , identified by their names, being suckled by the she-wolf. The Mosaic was found in Apamea in Syria, dated 511 AD . Apameia was a colony founded by Alexander's general Seleucos Nicator. Now the mosaic is in the Caravanserai Museum, Syria. Our books say that Romulus and Remus found Rome. Their story is recorded also by many "ancient" authors who claim their birth and adventures were fated in order for Rome to be founded. There is something very strange in this mosaic.  Our books say it is a Roman mosaic.  If he/she was a Roman, the question is why he/she did not write it in Latin but used an alphabet that we call it today ancient Greek alphabet?  If he/she was a Greek, why would he/she lay a Roman theme mosaic? What is written there?  What language is it?  What are these people that are Roman but write in ancient Greek? There are written these words; "piho" , "gsis" , "dve", " gon...

Does CMM correct a bad fixturing of a workpiece? Does CMM correct the impact that a bad fixturing has  on GD&T's, lengths, diameters and angles ? I think, the part fixturing and part alignment into the fixture is the main factor in CMM incorrect measurements. If we define the part fixturing and alignment incorrectly as a concept the CMM will be used incorrectly.  If the CMM result of a trueposition of a feature to datum -A- is out of the tolerance can the CMM correct the true position if it the datum A is measured as a cylinder and the part is 3 degrees skewed from being parallel to the CMM axis. I never have assumed that the CMM corrects the errors of fixturing, and the part can be measured without a precise fixturing/alignment. First question I will ask is what’s our benefit if the CMM does that? We do not need a precise fixturing-alignment of the part into a fixture and consequently we save some time/cost on this. Practically, how it is going to work when w...

It’s all about the measurement variations and correcting the factors that contribute on it. Measurement variations can come from three main sources: the person using the gage, person to person and part to part. It is also the gage itself a factor. MSA studies exist to discover and quantify the amount of variation coming from these different sources, so that corrective action may be taken if necessary. There are too many formulas of Gr&R studies. It depends from our intention: 1) To discover the amount of variation coming from three main sources. We need the data of one dimension-measurements(a) of three persons(b) for 10 parts(c), taken from Measurement Systems Analysis Reference Manual, 3rd edition (Chrysler, Ford, General Motors Supplier Quality Requirements Task Force). Ten parts were selected that represent the expected range of the process variation. Three operators measure the ten parts, three times per part, in a random order. 2) To examine the accuracy of a gauge, how a...

Is it possible to use the minor diameter of a spline as  a  datum  when the print requires to check the GD&T’s of other features to a spline datum? In this days, it is known that the Spline Gauges are the best inspection tools to check the splines. Spline gauges have an advantage over old methods of checking spline dimensions because the use of spline gauges not only ensure the quickest process for acceptance, which means also less timing cost, but also eliminates the need to inspect the profiles with old ways such as three pins method, pin+dial indicator methods,etc.   By using ‘GO’ and ‘NO GO’ spline gauges and plain ‘GO’ and ‘NO GO’  we ensure: 1    1)    ‘GO’ spline plug gauge checks the profile flank , the equally spiced angles  for all teeth, the extension of the root radius to the pitch circle diameter, pitch circle diameter and the runout of pitch circle diameter to major diameter of spline.     ...

The rules for determining Pre-Plate pitch diameters, major diameters, and minor diameters of thread rings, thread plugs, and plug  gauges are as follows: To determine  Pre-Plating  dimensions for external threaded parts:  For external threads subtract the max plating thickness from the high limit Pitch Diameter, and then subtract the minimum plating from the low limit Pitch Diameter   For the minor and major diameters reduce the maximum diameters by half the maximum plating and reduce minimum diameter by half the minimum plating.    To determine  Pre-Plating  dimensions for internal threaded parts:  For internal threads add the max plating thickness to the low limit of the Pitch Diameter, and then add the minimum plating thickness to the high limit of the Pitch Diameter.  For minor and major diameters incr...