Grinding Wheels Technical Information
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Basics of... Grinding Wheels
Toolroom Wheel Types (Used for Surface, Cylindrical and Tool & Cutter Grinders)
White: Light Grinding Applications - Produced with friable white aluminum oxide abrasive grain used for grinding heat sensitive steels and for easy to medium grind high speed steels.
Pink: Light to Medium Grinding Applications - Produced with fused aluminum oxide alloyed with chromium and titanium oxide. Excellent shape retention. Ideal applications include the working of alloyed and heat-sensitive steels.
Ruby: Medium to Heavy Grinding Applications - Produced by fusing high purity calcined alumina together with chromium oxide. Wheel is very versatile for grinding a wide variety of tool steels, with excellent form holding capabilities.
Blue/Gray: Medium to Heavy Grinding Applications - Produced with sharp, monocrystaline, friable aluminum oxide. Aggressive, and known to keep well defined cutting edges and shape retention. Off/white to blue/gray in appearance.
Ceramic: Light to Heavy Grinding Applications - Produced with ceramic alumina mix, this wheel is the best choice for grinding various tool steels. It has the highest productivity, fastest stock removal rate with the longest life.
Grade Selection Assistance
- Use coarser grits when finish is not important, rapid stock removal is necessary and there's a large contact area
- Use finer grits when finish is important, form needs to be held and there's a small contact area
| Grit Size | Particle Size | Finish RMS | Finish |
|---|---|---|---|
| 46 | .020 | Over 32 | Industrial |
| 60 | .016 | 15-20 | Smooth |
| 80 | .0105 | 12-18 | Fine |
| 100 | .0085 | 10-15 | Finer |
| 120 | .0056 | 8-12 | Very Fine |
| 150 | .0048 | 6-10 | Mirror Finish |
| 220 | .0026 | 5-6 | Mirror Finish |
Choosing the Hardness of a Wheel
Hardness: The hardness of a wheel is dependent on the holding power of the bond, which is what holds the abrasive grains in the wheel. The amount of bond in a wheel is the most important factor in determining the hardness of a wheel.
| Very Soft | Soft | Medium | Hard | Very Hard |
|---|---|---|---|---|
| D, E, F, G | H, I, J, K | L, M, N, O | P, Q, R, S | T, U, V, W, X, Y, Z |
The information in this chart follows industry standards
The following guide will help determine the hardness grade to use, but the type of stock, RPM and finish required all play a part in the determination:
| Softer Grades | Medium Grades | Harder Grades |
|---|---|---|
| Hard metals, such as hard tool steels, carbide | Hard and soft metals | Soft metals |
| Rapid stock removal is most important | Balance between rapid stock removal and longer life | Longer wheel life is most important |
| Large surface contact | Medium surface contact | Small, narrow surface contact |
Tips:
- Wheel has short life: change to a harder grade
- Need freer cutting action: change to a softer grade
- Need cooler cutting: change to a harder grade or a porous grade
- Wet grinding allows for harder grades to be used without burning the work
Bench & Pedestal Grinding Wheel Types (Wheels Used for Off-hand Grinding)
Gray: Produced with semi-friable aluminum oxide grain. Used for steel applications.
Green: Produced with friable silicon carbide abrasive grain. Used for non-ferrous applications and sharpening carbide.
Safety Tip: Grinding wheels should be used properly following all manufacturer′s safety instructions.
Grade Selection Assistance
Grit Selection for Aluminum Oxide
| 36 Grit | Coarse grinding |
| 46 Grit | Coarse to Medium grinding |
| 60 Grit | Medium grinding |
| 80 Grit | Medium grinding |
| 120 Grit | Fine grinding |
Grit Selection for Silicon Carbide
| 60 Grit | General Purpose/Rough grinding |
| 80 Grit | General Purpose grinding |
| 120 Grit | Fine Finish grinding |
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