Grinding Wheel for the Welding Job
Abrasive—Grits and Grains
The most common abrasive in grinding wheels is aluminum oxide. Typically, it is the abrasive you use for grinding the following:
- carbon steel
- alloy steel
- high speed steel
- annealed malleable iron
- wrought iron
- bronzes and similar metals
Another family of abrasives is zirconia alumina. This aluminum oxide and zirconium oxide combination results in a tough, durable abrasive that works well in rough grinding applications.
Silicon carbide is another common abrasive for grinding the following:
- gray iron
- chilled iron
- soft bronze
- other non-ferrous materials
Once you know the grain, the next question relates to grit size. All grinding wheels contain a number designating this characteristic. It corresponds to the number of openings per linear inch in the final screen size utilized to size the grain.
Allowing the abrasive in the wheel to cut efficiently requires that the wheel to contain the proper bond. It must also wear away as the abrasive grains wear and expell so there’s exposure to new sharp grains.
There are three principle bond types in conventional grinding wheels. Each of which, is capable of giving distinct characteristics to the grinding action on the wheel. The type of bond chosen depends on such factors as the following:
- wheel operating speed
- the type of grinding operation
- the precision required
- the material you’re grinding
The majority of grinding wheels have vitrified bonds, consisting of a mixture of carefully selected clays. The clays and the abrasive grains fuse into a molten glass condition at the high temperatures produced in the kilns where grinding wheels are made. The glass forms a span that attaches each grain to its neighbor and supports the grains while they grind during cooling.
Some bonds consist of organic substances. They soften under the heat of grinding. Resinoid bond is the most common organic bond type. It consists of synthetic resin. Grinding wheels with resinoid bonds are ideal choices for applications that require rapid stock removal, as well as those where better finishes are necessary.
Rubber is another type of organic bond. Rubber bonds offer a smooth grinding action, and are common in wheels where a high quality of finish is necessary, such as ball bearing and roller bearing races. They are also common for cut-off wheels where you hold burr and burn to a minimum.
The wheel comes in various shapes, the most common being the straight wheel. The grinding face is the part of the wheel that addresses the work. It is on the periphery of a straight wheel. A common variation of the straight wheel design is the recessed wheel.
Some wheels have the cutting face on the side of the wheel. These wheels are typically named for their distinctive shapes, as in cylinder wheels, cup wheels and dish wheels. Bonded abrasive sections of various shapes are sometimes assembled to form a continuous or intermittent side of grinding wheel. These products are called segments. Wheels with cutting faces on their sides common to grind the teeth of cutting tools and other hard-to-reach surfaces.
Mounted wheels are small grinding wheels with special shapes. These shapes include cones or plugs that are permanently mounted on a steel mandrel. The are common for various off-hand and precision internal grinding jobs.
Putting it All Together
You must consider numerous factors to select the best grinding wheel for the welding job. These factors include the following:
- Material you are grinding. This determines the kind of abrasive you will need in the wheel.
- The amount of stock you’re removing. Coarser grits provide rapid stock removal since they are capable of greater penetration and heavier cuts.
- Area of grinding contact between the wheel and the workplace. Use a wheel with coarser grit and softer grade for a broad area of contact to ensure a free, cool cutting action under the heavier load imposed by the size of the surface to be ground.
- The severity of the grinding action. This is the pressure under which the grinding wheel and the workpiece are brought and held together.
- Grinding machine horsepower. Generally, it’s necessary to use harder grade wheels on machines with higher horsepower.
These are just a few aspects to consider for selecting the right grinding wheel for the welding job. Contact Brazos Industries with the link below for more information on grinders!