GD&T Tutorial 13A : Rule #1

GD&T Tutorial : Rule #1 : Part 1 - In this Video, You will get the explanation of Rule #1 in Geometric Dimensioning and Tolerancing Tutorial

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Rule #1 Statement
Where only a tolerance of size is specified, the limits of size of an individual regular feature prescribe the extent to which variations in its geometric form as well as in its size are allowed

Rule #1 is also called as
1. Perfect Form at MMC Rule
2. Envelope Principle
3. Individual FOS Rule

Rule #1 Requirements
1. The Actual Local Size of the regular FOS at each cross section shall be within the specified size tolerance
2. Where a regular FOS is produced at MMC. It must have perfect form
3. When the actual local size of a regular FOS departs from MMC towards LMC, a variation in form is all0wed equal to the amount of departure.
4. There is no requirement for a perfect form boundary at LMC. A part produced at its LMC limit of size, is permitted to have maximum form variation up to MMC Boundary
5. Rule #1 applies to regular Feature if size only.

Rule #1 Does not control the location, or orientation of feature of size, hence it is called Individual Feature of Size Rule.

[akhilchristapher]

Rule one is not applicable to the indicated dimension because the part produced at MMC should be in perfect form.
If I'm wrong please correct me

[yogeshshinde]

You are doing great Job sir. I become your fan sir. 😊😁

[prakashdeshpande]

Imagine a Dia 60 H7 ( 60.000 /60.045 ) hole is to be controlled for cylindricity. As per the rule 1, if the hole is at MMC, its form must be perfect. Further, if the hole departs from MMC, some deviation at cylindricity can be allowed depending upon the actual size of the hole, but not beyond 60.045. All this will mean that the second chamber of the feature control frame has to indicate 0.00 permissible tolerance with M modifier. But the M modifier is not allowed for cylindricity. This characteristic allows only RFS modifier. How to resolve this controversy ?

[David_HX]

To answer the question at the end of this video: I think not - Simply because the Diameter of 69/59 is stated as a "Basic Dimension" and is not associated with a FCF denoting which tolerance type, I.E. Cylindricity, Circularity with any modifiers (or lack of) such as MMC or LMC - Assuming it is RFS is a bad assumption when the entire format is outside of a Feature Control Frame as a GD&T associated dimension should be -

[prakashdeshpande]

Any reply to my earlier query raised six months ago?

[kshitizsinha]

Sir in the question the said feature of size can be measured by an vernier callipers. So how it is an irregular feature of size. we dont need an actual mating envelope to measure the diameter

[Pavankumar-beir]

Since it is an Irregular FOS rule #1 can't applicable

[simrannagi]

No rule 1 does not apply on this as there is no control of inner profile dia 59/61 with respect to outer diameter. So inner profile should be controlled concentrically from outer profile. Otherwise during its mating with mating part there may be problem and if it is not concentrically controlled then teeth size can vary because of shifting of centres.

[Kallem]

Rule#1 doesn't apply to the figure shown in the question as it is an irregular FOS and rule#1 is applicable to regular FOS

[nayeemrahiman]

What if the part is completely straight with LMC. will this obey rule 1

[DreamDynamicz]

hi palani sir, as we know the feature (regular) can have maximum form deviation when it is at LMC, is it possible to have all the form deviations at maximum level in LMC, like max straightness error + max cylindricity error

[venkatshivareddy]

Hello sir,
Limit dimensions are given, it means rule no 1 is applicable. we can apply.

[nabarajgairhe]

Rule no 1 dose not apply in this because, this is not regular feature of size. Diameter can be measured at the tooth, but its not regularu.

[srotadas]

Hi Sir, I think it is not applicable for Rule-1, as the feature is an irregular FOS type A and the Rule 1 is applicable for regular size.

[surenthramm]

the final ques- ans is no, rule #1 wont applied to that shape. because it is irregular feature of size and rule 1 applies to regular FOS

[akshaynimkar]

The arrow show only feature not the feature of size. Rule 1 applied only to regular fos.

[shivambahalaskar]

Because given geometry is not a regular feature of size

[vinayaknilajkar]

Dose the Rule #1 applies to internal dimensions like holes, slots etc? If then things are opposite when it comes to FOS, MMC & LMC?

[urielhernandez]

HI Palani, I think the answer is no, because the indicated diameter is an irregular FOS and the rule # 1 only applied in regular FOS. I will appreciate your opinion or correction.

[akshayk]

Answer is no, since it is not a regular feature of size.. Correct me if I'm wrong