Random Orbit Sanders: 5 or 3?
George VondriskaHave you ever wondered what the 3 or 5 on a random orbit sander means? You’re about to find out.
The name of this tool gives us a good clue about the meaning of the numbers. Random orbit sander. The pad moves in an orbit. 3 and 5 tell you how big the orbit is: 3 mm or 5 mm. The numbers indicate the distance from extreme left to extreme right, or extreme top to bottom.
A larger number = a bigger orbit and that means a more aggressive sander. In the perfect world you own two random orbit sanders, one to use at the start of your sanding process and one to use for finish sanding.
With its smaller orbit a 3 mm ROS is leaving much smaller orbit marks, so any marks left by sanding are much harder to see.
When it comes to a random orbit sander, are you a 5 or are you a 3? Here's the deal. This is a question that's come to me a bunch of times. What is the deal with calling the sanders a 3 or a 5? What it's about is the orbit of the sanders.
So think of the name random orbit sander. And a 3. What that tells me is that the orbit is a 3 millimeter orbit, meaning that from its extreme left to extreme right, extreme bottom to extreme top, it's moving 3 millimeters. If you're running a 5. Same theory applies.
It's 5 millimeters extreme left to right, top to bottom, so bigger orbit, what does that mean to us? A bigger orbit, more movement is gonna remove material faster. Smaller orbit is gonna be slower, but why would we want to do that? The sanding scratches will also be smaller. So in the perfect world, if you had the opportunity to own two tools for this, you'd want to own a 5 for your slightly more aggressive work and then a 3 for your finishing work.
In the realistic world, if you're only gonna own one, you're gonna see a little bit of a difference and scratch difference between the two, and the 3 millimeter is gonna give you a better surface when you're done. So to give it like an understandability, 3 millimeters is about 1/8 of an inch, 5 millimeters is less than 1/4 of an inch. So it's not a huge difference between the two, but again, given the opportunity to use them both, you'll notice a difference in stock removal between them. So that's the deal with when it comes to random orbit sanders, what's 5, what's 3, that's millimeters of orbit.
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