In your ongoing quest to find the right tool for every job, consider two pieces which have some similarities, but also can produce very different results depending upon the project you are undertaking.
What is a grinding wheel?
As its name suggests, it is a wheel used for cutting, grinding, or finishing metal or other objects. It’s usually constructed with abrasive particles that are bonded together.
What is a flap disc?
It is also an abrasive disc, but with a different design. While the grinding wheel resembles a circular flat sheet, a flap disc is made up of many overlapping smaller pieces or flaps that are connected to a central hub.
How are they the same?
The grinding wheel and the flap disc are both used for grinding metal and can do it effectively. Both have high cut rates, or high rates of metal removal, and exhibit long product life so you can get plenty of high-quality use for your money. Grinding wheels and flap discs are available in Type 27 and Type 29 shapes. Type 27 wheels are mostly straight wheels, while Type 29 wheels have an upward angle built into the grinding section. Grinding wheels are also made in Type 28 shapes, with a downward angle.
When is using a grinding wheel better?
Type 27 grinding wheels can be used for cutting as well as for grinding root-pass welds (where two pieces have been fused together) and hot-pass welds (the second pass that goes over a root pass). People who weld pipes use grinding wheels for this activity. Usually a grinding wheel has a slightly longer product life than a flap disc.
When is using a flap disc better?
If you want finer results—such as blending, polishing, and deburring—then a flap disc is the way to go. Grinding wheels cannot be used at all for polishing and offer limited blending. In fact, the grinding wheel finish is usually too rough to be considered “blending.” Flap discs are perfect for deburring (smoothing the rough edges on metal) because they don’t chatter like grinding wheels do.
Which is safer?
A flap disc failure could cause loose sections of paper to hit the user and the disc to go slightly out of balance. With a grinding wheel failure, the wheel can become violently out of balance and throw chunks of rock-hard material at the user. There is a big difference.
Which is more flexible?
You get many more grit size selections with a flap disc. Whereas grinding wheels are usually available from 24-46 grit (coarse to medium), flap discs are built from 24-120 grit (coarse to fine). The higher numbers signify finer grit, which will usually mean milder aggression, greater blending, better polishing, and more excellent deburring. Finer grits also exhibit longer life.