Tips for Buying a Grinding Wheel
There are many types of products available for an entire range of grinding applications in metalworking. Ending up with the wrong one can be costly, both in terms of cash and time, so be very careful when making a choice.
When looking to buy a grinding wheel in particular, first consider the material that you intend to use it on. This will clue you in on the best type of abrasive for the wheel.
For example, if you’re grinding steels and their alloys, you can use either aluminum oxide or zirconia alumina. Non-ferrous metals and cast iron, along with non-metals, are best ground using a silicon carbide abrasive.
Grinding hard yet brittle materials is usually done with a fine-grit, soft-grade wheel. Hard materials oppose the force of abrasive grains, dulling them rather fast.
In other words, when you combine a finer grit and a softer grade, fresh and sharp cutting points become available as the abrasive grains become dull and separate. On the other hand, if you plan to grind soft, ductile and easily penetrable materials, you can use a coarse-grit and hard-grade wheel.
Another thing to be considered when shopping for a grinding wheel is how much stock must be removed. The coarser the grit, the greater the penetration, the heavier the cut and the faster the stock removal. But if the material is too tough, you can use a slightly finer grit wheel, which has more cutting points, for faster cuts.
If you want to cut faster, go for a wheel with vitrified bonds. For smaller stock removal or if finish requirements are higher, choose resin, shellac or rubber bonds.
When deciding on a wheel bond, look into the wheel’s speed in operation too. Vitrified wheels should only run at a maximum of 6,500 surface feet per minute or the bond could break. Organic bond wheels are often the choice between 6,500 and 9,500 surface feet per minute.
If a higher speed is needed, wheels can be custom-made for the specific purpose. In any case, never go faster than the safe operating speed – probably expressed in rpm or sfm – stated on the wheel or its blotter.
Next to consider is the area of grinding contact between the wheel and the workpiece. The bigger the area, the coarser the grit and the softer the grade must be to achieve a smooth cutting action. Now look into the severity – the pressure that makes the wheel and the workpiece stick to each other – of the grinding action. Abrasives are made to withstand varying severity levels when grinding steel and its alloys.
Lastly, check the grinding machine’s horsepower. In most cases, higher grade wheels are used with machines with higher horsepower. A softer grade wheel is better to use if wheel diameter exceeds horsepower. Otherwise, use a higher-grade wheel.