Introduction
In tool rooms and die shops around the world, punch grinders (punch former machines) are essential for producing precision round components.
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Punches and ejector pins
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Core pins and guide pins
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Carbide round bars and blanks
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Precision cylindrical components
These parts are typically made from tungsten carbide – one of the hardest materials used in manufacturing.
Grinding carbide on a punch grinder requires a specialized wheel. The wrong wheel burns the carbide, wears out quickly, or produces poor surface finishes.
The industry standard? Resin bond diamond grinding wheels.
In this article, we'll explain why resin bond diamond is the preferred choice for punch grinder operations on tungsten carbide – and how to get the best performance from your wheel.
Part 1: The Punch Grinder – What It Does
A punch grinder (also called a punch former or profile grinder) is a specialized grinding machine used for processing round bars and cylindrical components.
Typical Operations:
| Operation | Description |
|---|---|
| OD cylindrical grinding | Reducing diameter to precise size |
| Step grinding | Creating stepped diameters |
| Radius grinding | Grinding radii on punch tips |
| Taper grinding | Creating tapered profiles |
| Shoulder grinding | Grinding shoulders and flanges |
Typical Workpieces:
| Workpiece | Material | Hardness |
|---|---|---|
| Punches | Tungsten carbide | HRC 55-65 |
| Ejector pins | Tungsten carbide | HRC 55-62 |
| Core pins | Tungsten carbide | HRC 58-62 |
| Guide pins | Tungsten carbide | HRC 60-64 |
| Carbide round bars | Cemented carbide | HRC 50-65 |
Common Machine Brands:
| Brand | Models |
|---|---|
| Wasino | G-Series |
| Amada | Punch grinders |
| Proth | Punch formers |
| Chevalier | Punch grinders |
| Kent | Punch grinders |
| Okamoto | Punch grinders |
Part 2: Why Diamond for Tungsten Carbide?
Tungsten carbide is extremely hard (HRC 55-65 / HV 1,300-1,800). Only diamond abrasive can grind it efficiently.
Abrasive Comparison:
| Abrasive | Suitability for Carbide | Reason |
|---|---|---|
| Diamond | ⭐⭐⭐⭐⭐ Excellent | Hardest – cuts carbide efficiently |
| CBN | ⭐⭐ Poor | Not hard enough for carbide |
| Silicon Carbide | ❌ | Not suitable |
| Alumina | ❌ | Not suitable |
Diamond Advantages:
| Feature | Benefit |
|---|---|
| Extreme hardness | Cuts carbide efficiently |
| Sharp cutting edges | Produces smooth surfaces |
| Low friction | Less heat – prevents burning |
| Long life | Consistent performance |
Part 3: Why Resin Bond for Punch Grinding?
Resin bond diamond wheels are the preferred choice for punch grinder operations.
Bond Type Comparison:
| Bond Type | Characteristics | Suitability for Punch Grinding |
|---|---|---|
| Resin bond | Sharp, cool grinding, good finish, self-sharpening | ⭐⭐⭐⭐⭐ Excellent |
| Metal bond | Long life, runs hotter | ⭐⭐⭐ Good |
| Ceramic bond | Hard, good form-holding |