How would you control the long channels on this part?

[[Je...]]

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Hello. The customer has asked for advice on how to modify/improve the characteristics on this print. The features needing control are the seven .0255-.0260 long, .0255-.0260 deep channels. The profile controls are completely up for modification and in fact need to be changed.

This print invokes ASME Y14.5.

Here is the crux of the issue: The channel size at any 2-point section is critical. However, the overall length of the channels, which is 14 inches, can allow generous straightness deviation because the mating parts that move through these channels are more like "al dente spaghetti." The same is true for the depth of these channels (any 2-point depth must be .0255-.0260).

How would you tolerance this print to maintain the 2-point .0255-.0260 channel width and depth requirements while allowing these same channels deviation in form, size and orientation over their entire 14 inch length?

• 1. Can the independency symbol be utilized here somehow?

• 2. Is it sufficient to only include the size tolerance and no geometric control since ASME Y14.5 is invoked, so rule #1 applies?

• 3. Can/should profile of a line be used, and if so, how do I set this up since the channels are probed parallel to the 14 inch length and not as individual curve section?

Any other thoughts?

Much appreciated.

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Much appreciated.

[[Ri...]]

You have 9 Sections along the X axis.
Create Alignments for each Section.
Apply the Profile per Section per Slot Feature.

[[Je...]]

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Thanks, Rick. The problem is not how to measure these features but rather how to tolerance them on the print. We are changing the print to better reflect the fit and function.

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[[Ke...]]

Probably too simplistic, but... if you are controlling the widths & depths wit +/- tolerancing, then couldn't you just change the profile callout, to a straightness requirement?

[[Je...]]

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Simple is often best. I think that's a good idea, Keith. I'll mull it over.
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[[Ro...]]

Hi Jeff,
What if you treated one side of the slot as an individual datum feature 7x, and the opposing side a profile to that individual datum feature 7x? Similar to using an irregular shape as a datum. You could more loosely control the datum side of the slot for it's position/orientation/form to the rest of the part, and tighten up the controls for the width.

[[Ri...]]

5.8.2 Form Control Does Not Apply (Exceptions to
Rule #1)
The control of geometric form prescribed by limits of
size does not apply to the following:

(a) items identified as stock, such as bars, sheets,
tubing, structural shapes, and other items produced to
established industry or government standards that
prescribe limits for straightness, flatness, and other
geometric characteristics. Unless geometric tolerances
are specified on the drawing of a part made from
these items, standards for these items govern the surfaces
that remain in the as-furnished condition on the finished
part.
(b) tolerances applied with the free state modifier.
(c) when form tolerances of straightness or flatness are
applied to a feature of size. See paras. 8.4.1.3 and 8.4.2.1.
(d) when the “independency” symbol is used. See
Figure 5-10 and para. 6.3.24.
CAUTION: Without a supplementary form control, the
feature form is uncontrolled where the “independency”
symbol is applied.
(e) when average diameter is specified. See subsection
8.5.

[[Ri...]]

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I didn't mean for that to be how to measure, but also how to tolerance. 😉
One profile per each of the 9 sections called individually.

[[Ke...]]

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...I suppose you would also need positions defined at the front & back of the features,