Verification of “R” type radii callouts

[TFig]

Our engineers often use the R symbol to designate a continuous smooth radius on a part. My problem comes from how this is to be interpreted during the First Article inspection? Do you just visually verify that there is a smooth continuous radius or do you actually measure and report an actual result?
Thanks!

 

[3DDave]

The question is ambiguous - what are they applying the symbol to control? Is it an undimensioned radius?

 

[Garland23]

The radius still has a number of some sort. Even if the R is not followed by a number, it's intended to be a smooth curve that blends with some adjacent dimensions. So I'd say that it's a real dim that should (ideally) be measured. But I suspect it's usually overlooked.
I'll await other input from QC folks here.

 

[Brian Malone]

If the specification is from your company's engineers and you are performing the FAI for your company, then this appears to be a question that should first be asked with your company team and not on a web forum. Your inspection should be to confirm the part meets the design intent and specifications of your engineering team, and they should be ensuring their intent and specification is clear for inspection. I suspect a simple conversation will get you an answer or it will point out an issue that your team can improve.

 

[TFig]

To clarify, the R callout is typically deployed by our engineers at the end of what might be a milled slot. Say a .500+/-.005 slot with R at the end. Before I retired we required our suppliers to use the slot width to determine the appropriate radius (.250 in this example) and report actual. The new QAEs interpret it as “just verify that I has some kind of radius”. There’s no verification of completeness of radius as to overall width or even that’s a radius and not some kind of manually created blend. It’s just a Visual verification.
What I am looking for is a specification rather than an interpretation which can change over time. Since I’m retired I can’t talk to our engineers and drafts people like I used to.

 

[3DDave]

There seems to be no explicit treatment in ASME Y14.5 of this situation. The assumptions are that there will be a single radius and that the radius surface is exactly tangent to the neighboring surfaces.

For a feature carefully made with a single linear cut by a good quality end mill that isn't too bad an assumption.

But if it is by using a profiling pass with a cutter that is smaller than the width of the nominal slot or if the radius ends are drilled in advance of the rest of the slot or if the feature is waterjet or EDM cut, there isn't a similar guarantee of the shape.

Even in examples of position tolerance combined with rounded end slots, the standard has no clarification.

One is stuck unless a profile tolerance is used, but that isn't friendly to the assumed variations in plus-minus control of slot length.

 

[ctopher]

A radius is implied tangent by default, therefor should be a continuous smooth radius.

Chris, CSWP
SolidWorks
ctophers home

 

[3DDave]

Even the standard does not require it to be a continuous smooth radius, except for a CR designation, and it doesn't specify how to determine tangency limits.

 

[drawoh]

TFig,

ASME Y14.5 allows you to apply an "R" to a radius to confirm that it is round. This works fine at the end of a slot. Such a radius is half the slot width. If you apply a profile tolerance all around the slot, the radius is inspectable.

Another any other circumstances I can think of, you need a number and a tolerance for the thing to be inspectable. Profiles get the job done.

--
JHG