What does it mean to dimension a drawing?
Definition Dimensioning is the process of specifying part’ s information by using of lines, number, symbols and notes . Lines to be used are always thin continuous line. 2. Symbol or abbreviation commonly found in a drawing are – “ diameter ” is represented by a symbol “ ”.
Why is the placement of your dimensions important?
The placement of dimensions is important for the fact that legibility is important when placing dimensions for your sketches. Designers need to fully dimension a part to provide the width, height, and depth so the person that is manufacturing the sketch doesn’t dimension it wrong.
Why are dimensions important in drawing?
The purpose of dimensioning is to provide a clear and complete description of an object. A complete set of dimensions will permit only one interpretation needed to construct the part. An extension line extends a line on the object to the dimension line.
What are the rules of dimensioning drawing?
Dimension lines should be spaced uniformly throughout the drawing. They should be spaced at least 3/8” from the object, and 1/4″ apart. 16. No line of the drawing should be used as a dimension line or coincide with a dimension line.
What are the rules for dimensioning?
1. Each dimension should be given clearly so it can be interpreted in only one way. 2. Dimensions should not be duplicated or the same information given in two different ways (dual dimensioning excluded).
What is double dimensioning?
Dual dimensioning is the drafting practice of using multiple units of measure in a dimension in the same direction of a feature.
What is limit dimensioning?
[′lim·ət də‚men·chən·iŋ ‚meth·əd] (design engineering) Method of dimensioning and tolerancing wherein the maximum and minimum permissible values for a dimension are stated specifically to indicate the size or location of the element in question.
What is basic tolerance?
A numerical value used to describe the theoretically exact size, profile, orientation or location of a feature or datum target… It is the basis from which permissible variations are established by tolerances on other dimensions, in notes, or in feature control frames.
What are the types of tolerance?
Types of Geometric Tolerances
- Form Tolerance (Form Deviation)
- Form Tolerance and Location Tolerance (Profile Tolerance of Line / Profile Tolerance of Plane)
- Orientation Tolerance.
- Location Tolerance (Location Deviation)
- Run-out Tolerance (Run-out Deviation)
- Maximum Material Condition (MMC) and Least Material Condition (LMC)
How is tolerance calculated?
Tolerance equals the difference between lower and upper limit dimensions. Example; for 0.500-0.506 inch the tolerance would be 0.006 inch. BILATERAL TOLERANCE : It is a way to express tolerance by using both minus and plus variations from a given size.
What is a H7 tolerance?
International Tolerance grades For example: H7 (hole, tapped hole, or nut) and h7 (shaft or bolt). H7/h6 is a very common standard tolerance which gives a tight fit. For a shaft of the same size, h6 would mean 10+0−0.009, which means the shaft may be as small as 0.009 mm smaller than the base dimension and 0 mm larger.
What is the value of H7 tolerance in ø 50?
ISO Tolerances
| Nominal Dimension | Tolerance Zone in mm (Internal Measurements) | |
|---|---|---|
| over | to | H7 |
| 18 | 30 | +0.021 0 |
| 30 | 50 | |
| 50 | 80 | |
What is tolerance answer?
1 : capacity to endure pain or hardship : endurance, fortitude, stamina. 2a : sympathy or indulgence for beliefs or practices differing from or conflicting with one’s own. b : the act of allowing something : toleration.
What is H7 g6?
Close running fit for running on accurate machines and for accurate location at moderate speeds and journal pressures. H7/g6. G7/h6. Sliding fit not intended to run freely, but to move and turn freely and locate accurately.
What does H7 p6 indicate?
Interference fits For example, using an H7/p6 press fit on a 50mm diameter: H7 (hole) tolerance range = +0.000 mm to +0.025 mm. p6 (shaft) tolerance range = +0.042 mm to +0.026 mm. Potential interference will be between −0.001 mm and −0.042 mm.
When would you use a shaft basis?
This system is generally used in industries where the shaft is important. e.g. propeller shafts. stepped shafts….Differentiate between hole basis system and shaft basis system.
| HOLE BASIS SYSTEM | SHAFT BASIS SYSTEM |
|---|---|
| 1. The size of the hole whose lower deviation is zero is assumed as the basic size. | 1. The size of the shaft whose upper deviation is zero is assumed as basic size. |
Is H7 a press fit?
H8/r7, H7/p6, H7/r 6, P7/h6, R7/h6 Pressed fits with guaranteed interference. Assembly of the parts can be carried out using cold pressing. Hubs of clutch disks, bearing bushings. H8/s7, H8/t7, H7/s6, H7/t6, S7/h6, T7/h6 Pressed fits with medium interference.
How tight should a press fit be?
A good rule of thumb is about . 001 per inch press fit.
What is a good press fit tolerance?
You can go even a bit tighter on smaller diameters, like up to . 003 for a really tight fit. For larger diameters the. 001 per inch over about 3″ is about right.
Which of the following is incorrect about tolerance?
6. Which of the following is incorrect about tolerances? Explanation: Loose tolerance results in increase in cost, assembly problems and poor performance of the product. Tight tolerance results in unnecessary machining and inspection time.
What is the actual deviation *?
What is the actual deviation? Explanation: Algebraic difference between a size and a corresponding basic size is called deviation. Limit deviations are upper and lower deviations. Algebraic difference of actual size with basic size is called actual deviation.
Which of the following is correct for TQM?
Which of the following is correct for TQM? Explanation: Quality strategies and values in TQM emanates from top.
Which of the following is incorrect about interchangeability?
Which of the following option is incorrect about interchangeability? Explanation: An interchangeable part is one that can be replaced with a similar part manufactured to the same drawing. It can be used in mass production with an economic oriented approach. Assembly time decreases as mating parts are interchangeable.
What is advantage of interchangeability?
Interchangeable parts are parts that are, for practical purposes, identical. They are made to specifications that ensure that they are so nearly identical that they will fit into any assembly of the same type. One such part can freely replace another, without any custom fitting, such as filing.
Which of the following is incorrect regarding sine bars?
5. Which of the following is incorrect regarding sine bars? Explanation: The sine bar is itself not a complete instrument or complete measuring instrument. Another datum like surface plates are needed.
What is meant by roughness?
Engineering Metrology Questions and Answers – Surface Roughness. Explanation: Imperfections are bound to be on surface and they take the form of succession of hills and valleys which vary in height and spacing which result in irregularity of the surface. Roughness is the form of these minute imperfections.
What is unit of roughness?
Average roughness is typically measured in either microns (µm) or micro-inches (µ-in, µ”). One micron equals roughly 40 micro-inches (µ”). Also note that “micron” and “micrometer” are equivalent, and both terms are commonly used. Key fact: Ra has units.
What is RA and RZ value?
Ra measures the average length between the peaks and valleys and the deviation from the mean line on the entire surface within the sampling length. Rz measures the vertical distance from the highest peak to the lowest valley within five sampling lengths and averages the distances.
How is Ra value calculated?
Ra is calculated as the Roughness Average of a surfaces measured microscopic peaks and valleys….That means you:
- Measure height across the microscopic peaks and valleys.
- Calculate the SQUARE of each measurement value.
- Calculate the MEAN (or average) of those numbers (squared).
- Find the square ROOT of that number.