Video summary

Ep: 3.6 | Engranajes normalizados: Conceptos básicos | Elementos de máquinas | Sin Ingedudas

Main summary

Key takeaways

Educational

Main ideas / lessons

  • Why gear standardization exists: To ensure interchangeability and compatibility between machine components made by different manufacturers, as long as they follow the same standard.
  • Standardization has limits: Even within standards, components must be compatible in size and fit (e.g., you can’t match a “very large” gear to a “very small” one; similarly, a screw and nut must match dimensions to work together).

Benefits of using standards (general to machine elements)

  • Design simplicity & cross-company compatibility: Components (e.g., screws, keys, shafts, gears) can be combined in systems without custom redesign.
  • Lower cost and faster manufacturing: Standard forms and dimensions let manufacturers optimize production.
  • Improved quality: Direct competition among companies producing the same standardized items encourages quality improvements.
  • Better availability: Factories can stock standardized parts because demand is predictable.

Standards are not laws

Companies may design non-standard components for internal needs, but they won’t automatically be compatible with other manufacturers’ standardized parts.

Goal of gear standards

Ensure gears can be:

  • Interchanged
  • Common/consistent in design
  • Able to mesh correctly within defined limits

How gear standards define compatibility (key conditions)

To allow three gears to mesh in pairs (any gear can mesh with any other), standards enforce conditions such as:

  • Same pitch

    • If gears have the same pitch, they have the same module (as previously introduced in the course).

  • Tooth geometry equivalence (same teeth throughout)

    • All teeth on a gear must be identical so engagement works regardless of tooth-to-tooth mounting position.

  • Root clearance (backlash avoidance concept)

    • Root clearance is tied to the relationship between addendum and the opposing gear’s addendum, limited so that:
      • Tooth heads and tooth roots do not collide
      • The gears mesh with no backlash (gap equals the mating thickness relationship)

  • Tooth thickness vs space (pitch circle rolling condition)

    • The standard aims for tooth thickness = tooth space (each equals half the pitch).
    • This ensures that when pitch circles roll relative to each other, there is no backlash.

  • Common tooth inclination/normal

    • Standards aim so that at the point of contact, teeth have the same normal (same inclination angle).

Types of gear standards and scope in this course

  • Many standards exist, but:
    • Most standardized cylindrical (and some bevel) gears use an involute tooth profile.
    • The video/course primarily focuses on cylindrical gears with involute profiles.

International standards used: ISO

  • Example: ISO 53 (cylindrical gear concepts).
  • In Spain: equivalent is UNE 18016 (same content, Spanish).

Other national standards

  • United States: AGMA standards are used instead.
    • Main difference: AGMA uses inches; ISO uses SI units.

Other standards beyond ISO/UNE/AGMA

  • Standards also exist for other gear types (e.g., hyperbolic gears) and in other countries.

Non-standard (non-covered) gears exist

  • Some gears are proprietary or patented and not covered by a standard, but these are less common.

Specific ISO gear standard parameters mentioned

  • Generation angle

    • For ISO: 20°
    • Older standards used about 14.5°–15°, mainly for compatibility with older gears.

  • Modules (SI, in mm)

    • ISO provides a discrete set of acceptable modules in three series.
    • Series priority rule:
      1. Prefer Series 1
      2. If not possible, use Series 2
      3. If still not possible, use Series 3
      4. If no module exists in those series: cannot use a standardized gear “according to these standards.”
    • Since the number of teeth must be an integer, radii become constrained by the allowed module values.

ISO tooth geometry rules (addendum/dedendum)

General (normal teeth)

  • Addendum = module
  • Dedendum = 1/4 × module

These values ensure correct clearance and prevent collisions.

Short teeth (when normal teeth are unsuitable)

  • Addendum = 0.75 × module
  • Dedendum = 1 × module

Must be explicitly specified when ordering:

  • If you only specify width, module, and number of teeth → manufacturer defaults to normal teeth
  • To get short teeth → specify short teeth in the order.

Bottom clearance

  • For the mentioned relationships, bottom clearance is typically:
    • 0.25 × module
  • If gears are set further apart (not at the correct center distance), bottom clearance increases, which is generally undesirable.

Functional purpose of the small bottom clearance

  • Prevents collision between tooth heads/roots
  • Helps retain oil for lubrication between teeth

Instructions / procedure-like points (implicit ordering/design workflow)

When designing or ordering gears under ISO standards, ensure:

  • Select gears with the same generation angle = 20°
  • Choose a compatible module from ISO’s allowed module tables:
    • Series 1 preferred, then Series 2, then Series 3
  • Use standard involute tooth profiles (as covered in the course focus)
  • Ensure tooth geometry compatibility:
    • Tooth thickness and space set so thickness = space (half pitch relationship)
    • Addendum/dedendum matching the required ISO relationships
    • Verify bottom clearance behavior via correct center distance
  • If using short teeth, explicitly specify “short teeth” in the order; otherwise default is normal teeth.

Speakers / sources featured

  • Primary speaker: The course instructor (no name provided in the subtitles)
  • Referenced organizations/standards bodies/sources:
    • ISO (e.g., ISO 53)
    • UNE (e.g., UNE 18016)
    • AGMA (American Gear Manufacturers Association)
  • Referenced technical concept(s):
    • Involute gear tooth profile
    • Mentioned gear types: cylindrical gears, bevel gears, hyperbolic gears

Original video