Random Orbit Sanders - What are the holes for?

Pictured to the right is a random orbital sander, as some of you probably could tell pretty easily. I've looked at them quite often in my position at a tool company, and I've noticed the holes in the abrasive discs, but I hadn't ever really thought about what those holes were for. I just assumed they had a purpose, not really caring what that purpose was. Festool explained it nicely when they came in to give us product training, so I don't have to wonder any more.

Dust Extraction
Yes, since my previous post was talking about the dust extractor, this is again a dust extration technology. The holes are used to allow the sanding dust to collect in the bag on the back of the unit or in the dust extractor instead of bunching up and getting packed into the grit of the sandpaper. What a novel idea! Just one problem - if you apply suction to the sanding surface, it will be tougher to move the sander. While most vendors simply fix this issue by allowing for a suction leak out of the side of the pad, Festool has a patented active approach to the suction problem.

Guided Debris
By adding in a center hole which blows air out, the sander is no longer stuck to the surface of the material. But wait - it does more than that. By having the outer holes with vacuum and the inner hole blowing air, the result is actually an outward path of all debris to the collection points. Instead of just hoping that the holes eventually get close enough to the material, it now gets guided to where it needs to go and the sander becomes even more efficient. Festool calls this the "Jetstream principle". Other companies added that center hole to make them look the same, but after use there is just a large collection of sanding dust in that hole since it doesn't expel air.

Not Just Holes
When you really stop to consider it, those holes aren't just holes. They are an active part of making a random orbit sander work as it was intended. Knowing this, I may never look at holes the same way again - at least not on a tool.