In my opinion any axis ( being a line) can ask for straighteners. A plane surface can at the most ask flatness since it carries some length width combination.
Good video, thank you. Question: In a machine shop, what Flatness tolerance would be easy for the machinist to achieve? Also, what flatness tolerance would be deemed difficult to achieve with typical machining processes?
i dont have complete grasp on concepts of GD n T but i can tell that use of modifier of maximum material condition or any modifier is illegal on flatness geometric tolerance....we dont use modifier on flatness
@@PalaniKailash sir, you said , straight line is 2 D entity and flatness is 3 D dimensional entity. Please clarify how to choose those features (line , plane, circle, etc)which one is 2D and 3d. Any video refer or upload/suggest sir.
Sir then what about the flatness on bottom surface? Is it possible to control the flatness on both the surface (top and bottom)? Looking forward for your reply. TIA
The Derived Median Plane Flatness that the instructor is discussing here is for when it is important to control how bent a part is allowed to be. But, yes, you should always control the Size, Form, Orientation, and Location of every Feature of a part you design. So, yes, you would also specify the Form of the top and bottom surfaces with one of the Form controls, e.g. Flatness. You could also use Flatness for say, the bottom surface, declare that as Datum Feature "A" and then use a surface profile feature control frame for the top surface and make that profile dependent on Datum Feature "A". There are many ways to control the Form of a feature.
Derived Median Line Straightness and Derived Median Plane Flatness are different. Median Line is typically applied to cylindrical parts. Median Plane to rectangular parts. The Median Line is the set of points that you get inside of a cylindrical component when you take half the local diameter distance, for example, when measured with a caliper, for every cross section along the cylinder. For example, you could have a Median Line that is curved, as would be the case for a bent pin. Any Derived Median Line Straightness call out is an exception to Rule 1. That is, you don't have perfect form at MMC for the pin. That is, the envelope for perfect form for the pin would be the virtual condition for the pin. i.e. MMC + the Derived Median Line Straightness tolerance. Derived Median Plan Flatness is similar, but here you're dealing with a the Median Plane when dealing with for example a rectangular piece of material. Any Derived Median Plane Flatness call out is an exception to Rule 1. In the video, at time 3:51, the instructor is showing a Derived Median Plan Flatness of 0.1 mm. The MMC for that part, is 50.1. The Virtual Condition for that part, the perfect envelope for form, at its largest size, would be MMC + Median Flatness = 50.2. But, note the following: the Median Flatness tolerance here is specified at RFS (regardless of feature size). Therefore, the curvature of that rectangular piece of material would stay the same, at 0.1, no matter what the actual size of the part is between 49.9 and 50.1 At 4:05 in the video, the instructor added the MMC material condition modifier. What that means is that at MMC for the part, 50.1, it could be bent as much as 0.1. But, as the actual size of the part gets smaller, it can be bent more, i.e. Bonus Tolerance. For the case of the tolerance specified with the MMC modifier, the virtual condition of perfect envelope for that part is always the same at 50.2, no matter what the size of the rectangular chunk of material. In this case, you could build a jig with a perfect slot sized 50.2 to check every part built to see that it is not bent more than specified. But, obviously, you would still have to check the local size to make sure it meets the +- 0.1. Note that you would not be able to build a similar jig to make it easier to quickly check the part when it is specified with a tolerance for the Derived Flatness of 0.1 RFS.
No. The total variation of 0.2 is not divided between the top and bottom surfaces. When you take the Caliper and place it across the part, that size has to be between 49.9 and 50.1. For example, you could have the bottom surface come out of manufacturing such that it is perfectly flat, as unlikely as that could be. In that case, you could have all of the 0.2 variation on the top surface and still have a good part.
Form controls, "Flatness, Straightness, Circularity and Cylindricity, are describing a property of a feature WITHOUT any relationship to any other feature on the part. For example, a surface of a metal plate has a certain flatness to it. It doesn't matter how that surface is oriented or positioned with respect to any other feature. As a matter of fact, the Y14.5 standard makes it illegal to specify a datum reference in the DRF (Datum Reference Frame) of a feature control frame when using a Form control.
In my opinion any axis ( being a line) can ask for straighteners. A plane surface can at the most ask flatness since it carries some length width combination.
Good video, thank you.
Question: In a machine shop, what Flatness tolerance would be easy for the machinist to achieve? Also, what flatness tolerance would be deemed difficult to achieve with typical machining processes?
i dont have complete grasp on concepts of GD n T but i can tell that use of modifier of maximum material condition or any modifier is illegal on flatness geometric tolerance....we dont use modifier on flatness
Sir what is the difference between straightness and flatness tolerance when both are controlling peak and valley limits of a surface?
straightness is at one plane and it is 2D entity
Flatness is for entire surface, and it is 3D entity
@@PalaniKailash sir, you said , straight line is 2 D entity and flatness is 3 D dimensional entity. Please clarify how to choose those features (line , plane, circle, etc)which one is 2D and 3d. Any video refer or upload/suggest sir.
Sir then what about the flatness on bottom surface? Is it possible to control the flatness on both the surface (top and bottom)? Looking forward for your reply. TIA
The Derived Median Plane Flatness that the instructor is discussing here is for when it is important to control how bent a part is allowed to be. But, yes, you should always control the Size, Form, Orientation, and Location of every Feature of a part you design. So, yes, you would also specify the Form of the top and bottom surfaces with one of the Form controls, e.g. Flatness. You could also use Flatness for say, the bottom surface, declare that as Datum Feature "A" and then use a surface profile feature control frame for the top surface and make that profile dependent on Datum Feature "A". There are many ways to control the Form of a feature.
is Flatness tolerance is always less than the dimensional tolerance?
yes, when flatness is applied to surface
Sir, some of the videos in playlist are not playing. Getting some error..please have a look
will check
When applied to an axis (Feature of Size), Straightness and Flatness plays the same role? Please elaborate
Derived Median Line Straightness and Derived Median Plane Flatness are different. Median Line is typically applied to cylindrical parts. Median Plane to rectangular parts.
The Median Line is the set of points that you get inside of a cylindrical component when you take half the local diameter distance, for example, when measured with a caliper, for every cross section along the cylinder. For example, you could have a Median Line that is curved, as would be the case for a bent pin. Any Derived Median Line Straightness call out is an exception to Rule 1. That is, you don't have perfect form at MMC for the pin. That is, the envelope for perfect form for the pin would be the virtual condition for the pin. i.e. MMC + the Derived Median Line Straightness tolerance.
Derived Median Plan Flatness is similar, but here you're dealing with a the Median Plane when dealing with for example a rectangular piece of material. Any Derived Median Plane Flatness call out is an exception to Rule 1. In the video, at time 3:51, the instructor is showing a Derived Median Plan Flatness of 0.1 mm. The MMC for that part, is 50.1. The Virtual Condition for that part, the perfect envelope for form, at its largest size, would be MMC + Median Flatness = 50.2. But, note the following: the Median Flatness tolerance here is specified at RFS (regardless of feature size). Therefore, the curvature of that rectangular piece of material would stay the same, at 0.1, no matter what the actual size of the part is between 49.9 and 50.1
At 4:05 in the video, the instructor added the MMC material condition modifier. What that means is that at MMC for the part, 50.1, it could be bent as much as 0.1. But, as the actual size of the part gets smaller, it can be bent more, i.e. Bonus Tolerance. For the case of the tolerance specified with the MMC modifier, the virtual condition of perfect envelope for that part is always the same at 50.2, no matter what the size of the rectangular chunk of material. In this case, you could build a jig with a perfect slot sized 50.2 to check every part built to see that it is not bent more than specified. But, obviously, you would still have to check the local size to make sure it meets the +- 0.1.
Note that you would not be able to build a similar jig to make it easier to quickly check the part when it is specified with a tolerance for the Derived Flatness of 0.1 RFS.
What will be the total dimension in virtual condition of the part?
when flatness is applied to surface it will be MMC Boundary
When flatness is applied to FOS it will be OB or IB depending on the type of FOS
Sir, straightness and flatness looks to be same. What is the difference?
straightness is 2D applicable one particular plane
flatness is 3D applicable for entire surface
How we can get bounce tolerance .3 .2
when MMC is applied and the part departs from MMC condition of the part to LMC we get bonus tolerance
@@PalaniKailash thank you
here, the total allowed variation for both the sides are 0.2.and each side carries 0.1. how did you get 0.2 for one side?
correct me if I'm wrong..
No. The total variation of 0.2 is not divided between the top and bottom surfaces. When you take the Caliper and place it across the part, that size has to be between 49.9 and 50.1. For example, you could have the bottom surface come out of manufacturing such that it is perfectly flat, as unlikely as that could be. In that case, you could have all of the 0.2 variation on the top surface and still have a good part.
Sir why we dont use datum to form tolerances ?
@@GoodFoodGoodMood481 Thanks
Form controls, "Flatness, Straightness, Circularity and Cylindricity, are describing a property of a feature WITHOUT any relationship to any other feature on the part. For example, a surface of a metal plate has a certain flatness to it. It doesn't matter how that surface is oriented or positioned with respect to any other feature. As a matter of fact, the Y14.5 standard makes it illegal to specify a datum reference in the DRF (Datum Reference Frame) of a feature control frame when using a Form control.
Sir, VC =MMC+GT is not applicable for flatness?
when Flatness is applied to FOS, we get VC
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