Grinding Basics (Surface, Cylindrical, Internal) and When to Use It

Grinding is a finishing process that removes tiny amounts with a rotating grinding wheel, achieving high dimensional accuracy and a fine surface. A major strength is that it works even on hard materials after quenching. This article covers the types, wheels, when to use it, and cautions.

Types of grinding

Type	Target
Surface grinding	Finishing flat faces
Cylindrical grinding	Finishing the OD of round parts
Internal grinding	Finishing the ID of holes
Centerless grinding	Continuous OD grinding without centers (for volume)

How a wheel works and how to choose

A wheel's countless abrasive grains act as cutting edges. Selection points:

• Abrasive: alumina (general steel) / CBN, diamond (hard materials, carbide)
• Grit size: coarse = productivity, fine = better finish
• Bond hardness: too hard clogs (glazing), too soft wears fast

Choose the wheel by workpiece and required finish.

Advantages of grinding

• High accuracy: aims for micron-level accuracy
• Fine finish: smooth surfaces around Ra 0.2–0.8
• Handles hard materials: works even after quenching (high HRC)

When to use it

• As the final step in "rough machining → heat treatment → grind to finish"
• For dimension- and surface-critical areas: fits, shafts, sliding faces
• When you need accuracy or finish that turning/milling can't achieve

Cautions (grinding burn)

• Keep the allowance small (don't remove too much)
• Watch for burn, alteration, micro-cracks from grinding heat
• Prevent by: reducing feed, the right wheel, ample coolant

FAQ

Q. Why grind after quenching? A. Quenching hardens the material, making normal cutting difficult. Grinding can finish hard materials with high accuracy and a good surface.

Q. How smooth can grinding get? A. Generally around Ra 0.2–0.8. For smoother, use lapping/superfinishing.

Q. What is grinding burn? A. A defect where grinding heat alters/softens the surface or creates micro-cracks. Prevent it with feed, wheel choice, and coolant.

Conclusion

Grinding "finishes hard materials with high accuracy and a fine surface." Understanding its division of roles with cutting (turning, milling) makes process design smoother.

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