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Grinding wheel specification and selection

Short answer

The designation A 60 K 5 V indicates aluminium oxide abrasive, grit 60 (medium), grade K (medium hardness), structure 5 (medium spacing), and vitrified bond. Glazing is a smooth shiny surface from blunt grains (grade too hard); loading is pores clogged with chips (soft ductile metals). Truing restores shape and runout; dressing exposes sharp grains.

Explain the standard marking system of a grinding wheel with an example, such as A 60 K 5 V. What are glazing and loading of a grinding wheel? How are truing and dressing done?

A grinding wheel is a bonded mass of abrasive grains. Each grain acts as a tiny cutting tool, and the wheel renews itself as the dull grains break out and fall away.

Standard marking, example A 60 K 5 V

  A     60     K      5      V
  |     |      |      |      |
abrasive grit  grade structure bond
Letter or numberMeaningHere
AbrasiveA = aluminium oxide, C = silicon carbide, B = CBN, D = diamondAluminium oxide: steels
Grain sizeGrit number (coarse 10-24, medium 30-60, fine 70-180, very fine 220+)60 = medium
GradeHardness, A (soft) to Z (hard); the strength of the bondK = medium
StructureSpacing of grains, 1 (dense) to 15 (open)5 = medium
BondV = vitrified, S = silicate, R = rubber, B = resinoid, E = shellacVitrified

Selection guide

  • Steel and soft metals use aluminium oxide; cast iron, carbide and non-ferrous use silicon carbide.
  • Hard materials need a soft grade so that dull grains drop out; soft materials need hard grades.
  • Fine grit for good finish; coarse grit for fast removal.
  • Wide contact area or soft material needs open structure.

Glazing and loading

  • Glazing: the abrasive grains become blunt and the wheel surface turns smooth and shiny because the grade is too hard. Cutting efficiency falls, heat and burning appear.
  • Loading: the spaces between the grains fill with chips of the work material (soft ductile metals such as aluminium or copper). The wheel cuts poorly.

Truing and dressing

  • Truing restores the wheel shape and makes it run concentric, using a single-point diamond or a diamond roll.
  • Dressing restores sharpness and exposes new grains by removing the glazed or loaded layer, using a dressing stick, star dresser (Huntington) or diamond. Often both are done together.

✓ Answer checked by Claude Opus 5.5 (high effort)

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