Controlled Radius

[dgallup]

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.

My question is can a controlled radius ever be produced by single point turning? No matter how fine an increment the tool moves in it always leaves a small spiral tool mark. I think this constitutes a reversal in the surface. You may have to examine the part under a microscope but if I see single point turning marks I don't think it meets the definition of a controlled radius.

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The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.

 

[CheckerHater]

From the same paragraph (2009): “It is recommended that the CR be further defined with an engineering control specification”.
So define further.
Although it may not be easy. How good are adjacent surfaces? Should the arcs then be tangent to theoretical, derived, or actual surfaces? The definition of “fair”? How “fair” is “fair enough”?
The only bright side is that ISO isn’t that good defining “radius” either.
I guess if the radius really is “critical” profile should help. Otherwise just use regular radius, or resort to text note explaining the requirements.
Disclaimer: never used CR or similar control for the last 30 years

 

[powerhound]

I think the CR concept was incorporated to prevent gouging in radii rather than add an unachievable control.

John Acosta, GDTP S-0731
Engineering Technician
Inventor 2013
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