0
Datum dimensioning is where a single reference point is used for all dimensions in a single direction. E.g. If Point A is declared the reference point, then Points B, C, D, etc, will all be measured relative to Point A, not to each other.
Chain dimensioning is where each point is measured to the next. E.g. Point B is measured from Point A, Point C is measured from Point B, Point C is measured from Point B, and so on.
The problem with chain dimensioning is that each measurement relies on the accuracy of the previous measurement. If there is a tolerance associated with each measurement (+/- X), then the tolerance for each subsequent dimension accumulates and becomes the number of measurements times the tolerance of each measurement (+/- n*X).
Since datum dimensioning uses only one reference point, the tolerances cannot accumulate as each measurement is isolated, rather than relying on the accuracy of the previous measurement.
Common practice is to only use datum dimensioning in design drawings to ensure greater accuracy over the entire design without requiring tighter tolerances.
Add your answer:
Earn +20 pts
What is the difference between the hydraulic grade line and the energy line?
Hydraulic grade line is sum of Datum + Pressure Head Energy grade line is sum of Datum + Pressure Head + Velocity Head
What is the difference between hydraulic grade line and energy grade lines?
Energy gradient line refers to total energy excluding the losses due to flow. ie) Datum Head + Pressure Head + Velocity Head Hydraulic gradient line refers to the line joining upper and lower water surface levels excluding losses and velocity head. ie) Datum Head + Pressure Head
What is the origin for the word datum?
Datum is latin for "That which is a given, that which is taken for granted." Its plural is the more common "Data."
Would you use the word datum in sentence?
The datum supporting my argument comes from my experiment outlined in my report.
What is plural noun of datum?
Data
What is chain dimensioning?
It show dimension of given dig. Ex. length meter etc. > chain dimensioning as opposed to datum dimensioning. chain dimensioning: 4 holes in line on a drawing, first hole position dimensioned from the edge, remainder dimensioned from the centre of the previous hole. datum dimensioning: all holes dimensioned from the edge. the cumulative tolerance build up on the chain dimensioning allows for greater overall tolerance build up.
What is a datum point in drawing?
We have to make some choices when we dimension a block with a notch or cutout. It is usually best to dimension from a common line or surface. This can be called the datum line of surface. This eliminates the addition of measurement or machining inaccuracies that would come from "chain" or "series" dimensioning.
A primary datum requires how many points of contact?
According to ASME Y14.5, a primary dimensioning datum requires at least 3 points of contact to establish the datum plane. Two points of contact are required for the secondary datum and 1 point of contact is required for the tertiary datum.
What is a datum surface?
A datum surface is a reference surface used for dimensioning and tolerance purposes in engineering and manufacturing. It establishes the starting point for measurements and helps ensure consistency in the production and assembly of parts. Datum surfaces are key elements in geometric dimensioning and tolerancing (GD&T) standards.
Fixed common reference point for dimensioning?
A common reference point for dimensioning is typically established by defining a datum feature on the part. This datum serves as the starting point for all other dimensions and measurements on the part, ensuring consistent and accurate referencing throughout the design and manufacturing process. Establishing a fixed reference point helps to maintain precision and consistency in measurements and alignments.
How will you measure the height of a dam?
difference between the high flood level and stream bed datum.
What is the difference between a clue and a theory?
A clue is a datum - a fact. A "theory" tries to tell you what the fact means.
Difference between admiralty chart datum and mean sea level?
The chart datum is about 825 mm below the mean sea level. This is usually a showing of the average of the lowest tides.
What is the difference between the hydraulic grade line and the energy line?
Hydraulic grade line is sum of Datum + Pressure Head Energy grade line is sum of Datum + Pressure Head + Velocity Head
What id difference between data and datum?
Data is the plural, roughly meaning information. Datum is singular and is used someti es to mean a Landmark or starting point, a geodetic Datum point, like in the Grabd Canyon or the Promontory Point in Utah, both recognized landmarks.
what is dimensioning?
It show dimension of given dig. Ex. length meter etc. > chain dimensioning as opposed to datum dimensioning. chain dimensioning: 4 holes in line on a drawing, first hole position dimensioned from the edge, remainder dimensioned from the centre of the previous hole. datum dimensioning: all holes dimensioned from the edge. the cumulative tolerance build up on the chain dimensioning allows for greater overall tolerance build up.
What the vertical distance between lines in a paragraph?
Paragraph spacing.
