Tips for Buying a Grinding Wheel
In the world of metalworking, there are several products that can be used for a whole range of grinding applications. 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 shopping for a grinding wheel in particular, the first thing to consider is the material to be ground. This will tell you the type of abrasive that you'll need in the wheel.
For instance, to grind steels and steel alloys, you should use aluminum oxide or zirconia alumina. For non-metals, cast iron and non-ferrous metals, a silicon carbide abrasive will do.
A wheel with fine grits and a softer grade is usually used for hard but brittle materials. Hard materials contradict the force of abrasive grains, dulling them pretty quickly.
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. If the material you want to grind is ductile and easily penetrable, you should go for a wheel with a coarse grit and a hard grade.
Another thing you should look into when grinding wheel-shopping is the amount of stock for removal. The coarser the grit, the greater the penetration, the heavier the cut and the faster the stock removal. But if it's too hard to penetrate through the material, you can go for a slightly finer grit wheel, which tends to cut faster as there are more cutting points that will do the job.
For fast cutting, you can use a wheel with vitrified bonds. For higher finish requirements or to remove a minimum of stock, rubber, shellac or resin bonds work best.
Another thing you should consider when choosing a wheel bond is wheel's speed while in operation. Vitrified wheels should only run at a maximum of 6,500 surface feet per minute or the bond could break. Organic bond wheels enjoy the most demand, running anywhere from 6,500 to 9,500 surface feet per minute.
For higher speeds, customized wheels are needed. Whatever the case, always check the safe operating speed - usually in rpm or sfm - indicated on the wheel or its blotter, and make it a point never to go beyond it.
Yet another consideration to be made when buying a grinding wheel is the contact area between it 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. Take note that some abrasives can withstand more severe grinding conditions than others.
Finally, look into the grinding wheel's horsepower. Harder grade wheels are generally used with higher-horsepower machines. If wheel diameter is greater than horsepower, it is best to use a softer-grade wheel. Otherwise, a harder grade wheel fits well.
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