Profile Controls

What are Profile Controls?

There are two profile controls:

Profile of a Line (⌓)

FCF: ┌───┬──────┐
     │ ⌓ │ 0.2  │
     └───┴──────┘

           ╭──────────╮
          ╱    0.2     ╲  Tolerance zone follows
         │   ~~~~~~~~   │  theoretical profile
          ╲            ╱
           ╰──────────╯

Profile of a Surface (⌔)

FCF: ┌───┬──────┬────────┐
     │ ⌔ │ 0.5  │ A      │
     └───┴──────┴────────┘

    The entire surface must lie between
    two surfaces offset from the true profile

Profile Zone Types

Bilateral Equal (Default)

The tolerance zone is split equally on both sides of the true profile:

Tolerance: 0.4

         ═══════ +0.2 (outside true profile)
    ─────────── True Profile
         ═══════ -0.2 (inside true profile)

Bilateral Unequal

The zone is split unequally, specified by a note:

Tolerance: 0.4 (0.1 outside, 0.3 inside)

         ═══════ +0.1
    ─────────── True Profile
         ═══════ -0.3

Notation: 0.4 ⌔ A with note "0.3 INSIDE"

Unilateral

The entire tolerance is on one side of true profile:

Tolerance: 0.4 (all outside)

         ═══════ +0.4
    ─────────── True Profile
         (no zone inside)

Notation: Uses the ⓤ (unilateral) symbol or arrow indicator

Profile With and Without Datums

Without Datums (Form Only)

Controls only the shape of the surface:

┌───┬──────┐
│ ⌔ │ 0.5  │
└───┴──────┘

The profile can float and rotate—only shape matters.

With Datums (Form + Orientation + Location)

Controls shape AND position relative to datums:

┌───┬──────┬────────┬────────┬────────┐
│ ⌔ │ 0.5  │ A      │ B      │ C      │
└───┴──────┴────────┴────────┴────────┘

The profile must be located where shown relative to the datum reference frame.

Composite Profile Tolerance

Similar to composite position, controls both overall location and local shape:

┌───┬──────┬────────┬────────┬────────┐
│ ⌔ │ 1.0  │ A      │ B      │ C      │  ← Location to datums
├───┼──────┼────────┴────────┴────────┤
│ ⌔ │ 0.2  │                          │  ← Local refinement
└───┴──────┴──────────────────────────┘

• Upper segment: Profile located within 1.0 of datums
• Lower segment: Local form refined to 0.2

Profile Applications

Complex Curves

Profile is ideal for curves defined by equations, splines, or CAD models:

    ╭─────────╮
   ╱           ╲
  │  Airfoil   │  Profile tolerance follows
   ╲           ╱  the theoretical curve
    ╰─────────╯

Coplanar Surfaces

Multiple surfaces that must be flush:

Profile connects multiple surfaces
into one controlled zone:

    ┌─────┐     ┌─────┐
════╧═════╧═════╧═════╧════
     All surfaces in profile

All-Around Profile

The circle symbol indicates profile applies all around:

     ○
     │
┌───┬──────┬────────┐
│ ⌔ │ 0.5  │ A      │
└───┴──────┴────────┘

Applied all around the part outline

Profile vs. Other Controls

Key Takeaways

• Profile of a Line: controls 2D cross-sections
• Profile of a Surface: controls entire 3D surface
• Default is bilateral equal (split 50/50)
• Unequal or unilateral distribution specified by notes
• Without datums: form only
• With datums: form + orientation + location
• Profile is the most versatile GD&T control

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