Hard Vs Soft Grinding Wheels

The distinction between "hard" and "soft" grinding wheels refers to the bond structure, which is responsible for retaining the abrasive particles that cut. Softer bonds, regardless of label, are known to produce a more aggressive cut than harder bonds. With this in mind, let us investigate how the bond structure affects the grinding process.

1. The distinction between a hard and a soft grinding wheel

The abrasive renewal rate is the primary distinction between softer bonds (such as resin) and harder bonds (such as metal). This is the time required for the bond to wear down, releasing the dulled abrasive particle on the surface and revealing new, sharp grit for cutting.

Softer bonds wear faster, exposing new grit more frequently. This enables more aggressive cutting, whereas harder bonds retain the same surface particles for longer, making it difficult to remove large amounts of material quickly.

The resin is the softest bond, followed by polyimide, in order of softness to hardness. Abrasive concentration, on the other hand, can influence the hardness of the wheel. A C50 abrasive concentration wheel, for example, would be softer than a C100 with the same bond. The relative hardness of the wheel can also be affected by the run speed. A higher RPM can cause a soft bond to behave as if it were a harder bond, and vice versa. Finally, coolant (or lack thereof) has a significant impact on the performance of a grinding wheel. Harder bonds perform best in water-based coolant applications, while softer bonds perform best in oil-based coolant applications.

Softer bonds are best suited for dry grinding and oil-based coolant applications, but they can also be used in centerless grinding and CNC tool fabrication. Metal and hybrid bonds are frequently used in ceramic and glass working for grinding single-edged tools and fluting processes.

Finally, the wheel must be designed based on the grinding application, the material to be ground, the machine type and power, and the coolant type. Speaking with an application engineer ensures that the proper wheel bond and concentration are used for consistent grinding results.

2. Resin Bond Grinding Wheels: Formulations and Applications

The resin bond is one of the most commonly used grinding wheel bonds in the superabrasive market. There are virtually limitless options in terms of ingredient concentration when using phenolic or polyimide resin. But what makes the resin bond one of the most widely used bonds in the industry? Let's delve deeper into each type of resin, its applications, and its benefits to better understand why resin is so popular in so many different applications. Click here for Resin Wheel.

2.1 The Phenolic Resin

Phenolic resin is a synthetic polymer formed by the chemical reaction that occurs when phenol and formaldehyde are combined. This reaction promotes the formation of a thermosetting network polymer, in which the polymer chains interlink to form insoluble, hardened connections. The structure of the polymer chains has a direct impact on the resin's properties. Producing a more delicate, less heat-resistant heat resistant structure is ideal for grinding softer materials in this case. Phenolic resin bonds are commonly found in woodworking and mining wheels, but they are also a popular choice for general-purpose grinding. Phenolic resin wheels are suitable for wet and dry grinding and are also suitable for centerless grinding.

2.2 Resin Polyimide

A high-performance plastic polymer is a polyimide resin. This material is praised for its heat resistance as a soluble thermoplastic capable of withstanding temperatures ranging from below zero to 400 degrees Celsius under dry grinding conditions and 625 degrees Celsius under wet grinding conditions. Polyimide resin is ideal for high-tolerance grinding because it is a harder resin option with high thermal capacity. When compared to other bond types, these wheels have higher stock removal rates, better form holding, and excellent wear resistance. It's no surprise that they're favored by manufacturers in the round tool, aerospace, and automotive industries.

2.3 Resin Selection

Resin bond wheels are used in a wide range of manufacturing applications, including automotive component fabrication, semiconductors, and paper-converting wheels. The most important distinction to make when selecting a resin bond is the type of machinery. If the application is correct and you're working with a CNC machine, a poly bond may be the best option. If you are sharpening carbide-tipped tools with a low-power machine, phenolic resin is the best choice. Could a resin bond wheel be the right choice for you because of its versatility, dependability, and low cost?

Nobler Glass' application engineers have years of experience in creating the ideal bond option for your specific grinding operation. We provide ongoing support even after you have purchased your wheel. Our engineers believe in continuous improvement, so they design your grinding wheels to be as efficient as possible throughout the life of your grinding operation.

3. 101 Stellite Grinding

The satellite is a cobalt-chromium alloy that has recently become a popular substitute for carbide in woodworking tools due to its wear resistance. As stellite becomes more prevalent, many manufacturers discover that it is a particularly difficult material to grind. When using a general-purpose CBN wheel to grind stellite, the material is pushed along the surface rather than cut away. Large burrs form during the grinding process, revealing an uneven surface finish.

Many wheel buyers will already have a CBN wheel, but as previously stated, not all CBN wheels are designed to cut satellites. If you're a regular reader, you'll recall how we stressed the importance of considering the material to be cut when selecting the grit size, shape, and bond structure of your grinding wheel. CBN wheels with a blockier grit are intended for grinding hardened carbon steel. Stellite is a much more ductile material than carbon steel. Blockier CBN particles shear off bits of hardened steel easily but fail to completely remove the satellite from the grinding surface, pushing it along and creating large burrs.

Nobler Glass addresses this by incorporating a specially formulated CBN particle designed to cut satellites and minimize burrs generated during the grinding process. These sharper CBN particles, when combined with the more aggressive resin bond structure, can cut through satellites while maintaining a clean cutting surface ready for use on other viable materials. One of Nobler Glass' application engineers, John Coleman, provides the perfect analogy:

"It's like saying that squares are rectangles, but rectangles are not squares." Nobler Glass' CBN wheels are designed to grind satellites while also being able to be used on steel. General-purpose CBN wheels can only grind ferrous materials."

Do you require any additional information? If you require additional satellite grinding advice, the engineers at Nobler Glass are ready to help. Nobler Glass provides free consultations with no pressure!