Is the disc face up or down? And other angle grinder tips
Many people are concerned about how to install a disc correctly. Up or down. What are the consequences of improper installation?
Some believe the disc should be installed face down. That's right. And they have compelling arguments.
They believe that if the washer is facing down, the disc is perfectly level, eliminating any wobble or warping. Because the washer is flat. There's some logic to this.
However, look - there's a knurling on the support washer. This is common on all angle grinders. And if we install the disc with the thin metal facing the knurling, the knurling will be imprinted.
The washer won't be flat, and it won't be installed as level a second time.
Another argument:
The expiration date is imprinted on the metal surface of the disc. This is important information. And when we install the disc face up, when tightening the clamping nut, we slip slightly on the disc. This scratches the part where the expiration date is printed. After a few clamping cycles, the date becomes illegible. So it's logical to install the disc so the date won't get scratched—that is, face down.
But other people think the disc should be installed face up. Here's their reasoning:
All the important information about the disc is on its face. If we turn the disc over, the information will be hidden by the casing. Reading it is problematic. And you could accidentally grab the wrong disc.
It's logical that the knurling should bite into the softer material, thereby ensuring good grip. That is, not into the metal, but into the abrasive disc itself.
We know that the nut itself can't loosen. It tightens automatically when the tool is in use.
Tightening and holding the nut are never a problem. The only difficulty is loosening.
But loosening it is much easier when it's pressed against the metal rather than the abrasive. Metal slides much better on metal than metal on abrasive.
Therefore, logically, the correct position is when the nut is clamped against the metal.
Why is this metal washer even necessary? What is its function?
Its purpose is to center the disc on the spindle.
The main function of this washer is not the flat outer surface. The washer is needed to ensure that the disc sits evenly on the spindle. The working surface of the washer is the inner ring!
If there were no inner ring, then...
And the flat rim is needed solely to ensure that this ring sits securely on the disc.
Therefore, it doesn't matter whether you install it face up or face down. This doesn't affect the operation of the inner ring.
We've come to the answer to your question.
I might surprise you if I tell you that the mounting side of the disc is not regulated.
The side on which the disc is mounted has no significant effect.
Each disc has warning signs on it, such as the use of gloves, glasses, etc. The manufacturer always plays it safe by printing these warnings.
And if the position of the disc on the tool mattered at all, it would definitely be printed on the disc itself!
It's safe to say that the position of the washer doesn't play a significant role when mounting the disc. Some discs can only be installed in one position. These discs have a bottom washer, and some have a top washer.
The same goes for cutting discs—some have a top washer, and some have a bottom washer. This is because the working part of the washer is the inner ring.
For example, DeWalt places the disc face down in their advertising and training videos. However, this isn't due to the washer, but rather because both the grinder and the disc itself look equally attractive in this position when photographing and filming. This is purely a marketing gimmick.
So, you can position the disc however you like. It doesn't affect anything.