Amber was right. Per ASME Y14.5M (1994, unless the new versions have updated this), in Figure 6-8, it mentions that circularity is in terms of radius, not diameter. In the example of the video, we're analyzing a dimensional tolerance (and this video excels on how to interpret the diameter tolerance), but it does not address geometrical tolerance for circularity, as there is no circularity symbol in this example. As explained in the video, in terms of dimensional tolerance, the diameter can either be 19.5 or 20.5. If we add a circularity tolerance on top of that, let's say, of 0.25, and assuming our two measurements at 180 deg apart were 19.5 and 20.5, the dimensions are within tolerance, but the circularity would be (20.5-19.5)/2 = 0.5 mm. We would meet the dimension per its tolerance, but the part would be out of round.
@PlatonicVoyeur
Жыл бұрын
I think what's difficult to understand about this is that the large green circle represents MMC, but the smaller green circle does NOT represent LMC. It's actually 18.5mm. So if the part was perfectly circular at the small green circle, it would violate the size tolerance by 1mm. So the check for circularity is not "all points fall within the space between the circles," it's "all diametrically opposite points measure within the tolerance amount." What adds confusion is that the axis of the part is irrelevant. Right? It has to be - as you rotate the part to take 2-point measurements the axis of rotation is going to shift. But on your website: "Two concentric circles, one inner and one outer, in which all the points within the circular surface must fall into. The tolerance zone lies on a plane that is perpendicular to the central axis of the circular feature." "Circularity is measured by constraining a part, rotating it around the central axis while a height gauge records the variation of the surface. The height gauge must have total variation less than the tolerance amount." Can you please explain? I am not understanding how these descriptions match what's in the video.
@Gdandtbasics
Жыл бұрын
Thanks for the questions! For the first quote you mentioned, this describes exactly the tolerance zone for circularity. What's important to understand is that the diametric size of the circularity tolerance can change, so if we imagine two concentric circles that grow and shrink in size, the only requirement is that they stay radially spaced from each other by the tolerance value. Circularity will NOT control size, but size WILL control circularity. For the second quote you have, this measurement process is technically measuring runout to itself, which gets us very close to measuring for circularity. By measuring it this way we are being conservative.
@harikumar4757
23 күн бұрын
Sir, regarding article by GD&T basics on December 21,2014 I have doubt about circularity tolerance,in example (1) regarding dimensional tolerance mentioned the diameter is ∅10.0 with dimensional limit of ±0.08 FOR shaft If it's MMC, ∅ =10.0+0.08=10.08 If it's LMC, ∅. =10.0 -0.08=9.92 The difference between MMC and LMC is 10.08-9.92=0.16 My doubt is ,is this value 0.16 belongs to diametrically or radially. In first example it is shown radially (that is per side) . while calculating Radi of MMC is 10.08/2=5.04( Max Radi) Same way Radi of LMC is 9.92/2=4.96(Min Radi) According to first example limit tolerance is 0.16 So if this limit difference is adding to Radi LMC that is 4.96 +0.16=5.12 That is beyond the Radi MMC(5.04) If adding 4.96+0.08=5.04 My doubt is this 0.16 value ,total limit or perside limit .
@ashutoshsingh1137
Жыл бұрын
Distinguish between circularity vs cylindricity
@Gdandtbasics
9 ай бұрын
Circularity is the roundness of any given cross section, and cylindricity is the roundness of the entire cylinder as well as the "bow" or form of the cylinder.
@ian8084
10 ай бұрын
Your image is showing that the radial separation is 1 but it’s only .5. Circularity refers to the difference in Diameters not radii.
@Gdandtbasics
9 ай бұрын
Thanks for the comment! We get this confusion alot. The ASME Y14.5 states that circularity is the condition where all points of the surface are equidistant from the axis of that feature. The distance from the axis to the surface is the radius. Thus the value in the circularity tolerance zone is truly the radial distance between two concentric circles as we show. Hopefully this helps clarify things for you!
@rascalgirl8667
2 жыл бұрын
I WAS SEARCHING IT FROM 6 MONTH I FOUND TODAY
@jaxonrholden
2 жыл бұрын
I'm afraid you're incorrect my friends. In your illustration you show an outer boundary of 20.5, and an inner boundary of 19.5, yet show a RADIAL SEPARATION of 1.0. That's incorrect. The difference in diameters is 1.0, yes, but that means the radial separation is not 1.0, but half that amount- 0.5. And form controls are always called out with radial separation. Circularity of 0.5 means the radial separation must be, at most, 0.5. So the person asking the question about dividing by 2, I believe is correct. They're accounting for the fact the form control is radial, while the size tolerance is diametral. As you correctly stated, diameter must fall between LMC and MMC to meet size spec. If Circularity of 0.5 is violated, then the size is necessarily out of spec. It cannot but be out of spec.
@Gdandtbasics
2 жыл бұрын
Thanks for your comment! We get this misunderstanding quite often in our courses. Picture the black outlined part in our animation. If we were to check this part in accordance with the size dimension (ignoring the circularity control for now). Rule #1 as applied to a cylindrical feature will state that the cylinder cannot exceed an envelope of perfect form at MMC, thus requiring the outer boundary to be 20.5mm in this case. On the flip side, a size tolerance for external features states that the smallest 2-point measurement cant be any less than the lowest limit as dictated by the tolerances, which would be 19.5mm in this case. This 2-point measurement is not "centered" on the part thus allowing one of the points to potentially shift to the outer boundary limit as you see here. This part still passes the size check. Now bring in the green circles representing circularity, we see this is indeed a radial separation of 1mm which equals circularity of 1mm. Also, please note that form tolerances don't control the "size" of features. The tolerance zone only requires the radial deviation be held within 1mm. So a part could pass 1mm circularity, but fail the size tolerance.
@AugustoGrazioli
Жыл бұрын
Roundness tolerance is the difference between the radii of the concentric circles, not between the diameters.
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