🪨 Abrasives Reference Guide

Grinding wheel markings, abrasive types, grit sizes, and selection guide for common shop grinding applications.

Reading a Grinding Wheel Marking

A typical wheel marking like A 60 K 5 V breaks down as:

Position	Example	Meaning
1 — Abrasive Type	A	Aluminum Oxide
2 — Grit Size	60	Medium (60 grit)
3 — Grade (Hardness)	K	Medium (bond strength)
4 — Structure	5	Medium spacing
5 — Bond Type	V	Vitrified

Abrasive Types

Code	Abrasive	Best For
A	Aluminum Oxide (Al₂O₃)	Carbon steel, alloy steel, HSS — most common general-purpose abrasive
WA	White Aluminum Oxide	Tool & cutter grinding, HSS tools. Cooler cutting, more friable
PA	Pink Aluminum Oxide	Precision grinding of steels. Tougher than white, cooler than brown
C	Silicon Carbide (SiC)	Cast iron, non-ferrous metals, stone, glass, carbide (green SiC)
GC	Green Silicon Carbide	Carbide tool grinding, ceramics. Sharper than black SiC
CBN	Cubic Boron Nitride	Hardened steels (55+ HRC), superalloys. Second hardest material
D	Diamond	Carbide, ceramics, glass, PCD. Not for steel (carbon diffusion)

Grit Size Guide

Grit Range	Classification	Typical Use	Approx. Ra (μin)
8–24	Coarse	Heavy stock removal, snagging, rough grinding	100–250
30–60	Medium	General-purpose grinding, most shop work	32–100
70–120	Fine	Finish grinding, tool sharpening	16–32
150–240	Very Fine	Precision finish, honing, lapping	8–16
280–600	Superfine	Superfinishing, mirror finish	2–8

Grade (Bond Hardness) Scale

Letters A through Z, where A is the softest grade and Z is the hardest:

Range	Grade	Use
A–G	Soft	Hard materials (hardened steel, carbide). Grains release quickly to stay sharp.
H–P	Medium	General-purpose. Most common for shop grinding.
Q–Z	Hard	Soft materials (aluminum, brass). Grains held longer before releasing.

Rule of thumb: Hard material → soft wheel. Soft material → hard wheel. This ensures grains shed before they become dull and burn the work.

Bond Types

Code	Bond	Notes
V	Vitrified	Most common. Glass-like ceramic bond. Good for precision grinding. Brittle but excellent form holding.
B	Resinoid	Resin bond. More flexible, used for cutoff wheels and heavy stock removal. Higher speed capability.
R	Rubber	Used for regulating wheels in centerless grinding and thin cutoff wheels.
M	Metal	Used for diamond and CBN wheels. Strong grain retention for heavy-duty work.
E	Shellac	Produces excellent finish. Used for cam and roll grinding.

Quick Selection Guide

Application	Recommended Wheel
Surface grind mild steel	A 46 K 5 V (aluminum oxide, medium grit, medium grade, vitrified)
Surface grind hardened steel	WA 60 H 5 V (white alox, fine, soft grade) or CBN
Sharpen HSS tools	WA 60 J 5 V (white alox, medium-fine, medium-soft)
Grind carbide tools	GC 60 J 5 V (green SiC) or D (diamond wheel)
Cylindrical grind steel	A 60 K 5 V (standard alox, medium)
Cut-off steel bar	A 36 R BF (coarse, hard, resinoid reinforced)
Grind cast iron	C 36 K 5 V (SiC, medium, vitrified)
Polish/finish stainless	A 120 J 5 V (fine grit, medium-soft)

Sandpaper & Coated Abrasives

For hand deburring and finishing:

Grit	Use
60–80	Heavy material removal, weld grinding
120–150	General deburring, blend scratches
220–320	Pre-finish, preparation for paint/coating
400–600	Fine finish, between coats
800–1500	Polishing, mirror prep
2000+	Wet sanding, mirror finish

Scotch-Brite/non-woven pads: Coarse (maroon) for deburring → Medium (green) for blending → Fine (gray) for finishing → Ultra Fine (white) for polishing.