CR Usage question
CR Usage question
(OP)
We are designing a part for a client. This is a cylindrical body with a threaded counter bored hole. Originally I had the outside edge of the part designed with a chamfer (the client had this on their preliminary drawings). Now they wish for some freedom to make this corner either a chamfer or a radius. To allow this freedom while still constraining the feature they asked for a CR callout.
I am not familiar with this callout and actually had to look it up on the internet, where I got the following definition:
Controlled Radius - creates a tolerance zone defined by two arcs (the minimum and maximum radii) that are tangent to the adjacent surfaces. Where a controlled radius is specified, the part contour within the crescent-shaped tolerance zone must be a fair curve without flats or reversals. Additionally, radii taken at all points on the part contour shall neither be smaller than the specified minimum limit nor larger than the maximum limit.
This does not sound as if it will work the way the customer thinks, but I have never used it.
Is there an accepted way to define a corner feature as either a chamfer or a radius but limiting it to a specific size?
Thanks,
I am not familiar with this callout and actually had to look it up on the internet, where I got the following definition:
Controlled Radius - creates a tolerance zone defined by two arcs (the minimum and maximum radii) that are tangent to the adjacent surfaces. Where a controlled radius is specified, the part contour within the crescent-shaped tolerance zone must be a fair curve without flats or reversals. Additionally, radii taken at all points on the part contour shall neither be smaller than the specified minimum limit nor larger than the maximum limit.
This does not sound as if it will work the way the customer thinks, but I have never used it.
Is there an accepted way to define a corner feature as either a chamfer or a radius but limiting it to a specific size?
Thanks,





RE: CR Usage question
“Know the rules well, so you can break them effectively.”
-Dalai Lama XIV
RE: CR Usage question
Your requirement is exotic enough that even if there was something in the standard, no one would understand it.
How about a detail view showing the alternate corner? You can implement this in 3D CAD by having two configurations of the part.
--
JHG
RE: CR Usage question
RE: CR Usage question
As for "chamfer or radius" drawing specification, this is quite common practice used in different specifications throughout industry. A letter is used instead of a numerical value and a leader associated with that letter points to the edge. Then additional chart says that this letter is for chamfer or radius and a certain value is given.
The thing is this approach works for 45° chamfers. If chamfer is other than 45°, other ways must be figured out.
BTW, per Y14.5 standard it is not allowed to specify chamfer by a note, like 0.5 X 30°, for angles other than 45°.
RE: CR Usage question
RE: CR Usage question
RE: CR Usage question
Also becareful with .05*45° type call outs. Depending on how critical the chamfer size is and what tolerance you have on angles you may not get what you want. These days I more often use .05 *.05 type call-outs or dimensions schemes due to this.
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: CR Usage question
I claim a brain fart.
“Know the rules well, so you can break them effectively.”
-Dalai Lama XIV
RE: CR Usage question
If the chamfer (or radius) is really critical, I do not think any of the methods is good option.
Here is the snapshot from ISO 14405-2:2011:
http://files.engineering.com/getfile.aspx?folder=2...
If we additionally notice that the vertical and horizontal edges on figures b) and d) are perfectly straight and perpendicular to each other, while in reality this is quite unlikely to happen, the situation with "traditional dimensioning of chamfers and radii" becomes even more complicated.
RE: CR Usage question
Here is an example of "radius or chamfer" interpretation. It is not explicitly endorsed by any standard, more of a common sense (if such exists)rule.