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8

In addition to Rob's answer, the motion of both sanders is a bit different. Sheet sanders tend to move back and forth in a straight line, with small variation side to side. A random orbit sander has an eccentric cam mechanism that makes the sanding disc move in a circular but not round fashion. I'd best liken it to the old spir-o-graph toy- it's 'orbiting'...


8

A lower speed can be desirable if you're sanding between thin coats of finish or thin veneers, and you don't want to sand through the current coat or the veneer. But many of the lower-end or homeowner-grade random orbit sanders aren't aggressive enough for it to matter. As with many tools, lower speeds on a sander offer more control, so you may avoid ...


7

Sheet sanders usually take 1/4 or 1/2 sheet of sandpaper held in place with 2 clamps, though some can also take hook-and-loop paper. As Graphus pointed out, most models today have dust collection. Many models come with a hole punch in order to perforate standard sheets of sandpaper with the appropriate pattern of dust collection holes, but for some you must ...


5

When you want to sand more aggressively, you use a faster speed. When you want to sand more gently (to take greater care not to sand through veneer or finish for example) you would drop to a lower speed1. Just to note, final sanding of wooden surfaces should normally be done by hand to help reduce the chance of 'pigtails' or sanding swirls2 and to ensure ...


5

My question is, since the grain raises and I have to re-sand it anyway, do I really need to sand it before priming? Birch has a tendency to be a bit stringy even after sanding, so this could be what you're experiencing. If you're painting, you can probably get away with a less-smooth surface than if you were using a film finish like clear polyurethane. ...


5

Variable speed sanders are most useful for heat sensitive materials, which wood is not. (At least not to the range of temperatures that sanding will generally expose it too!) A variable speed sander can help control the amount of material removed if you're just trying to make a light pass though.


4

Random orbit sanders rotate and oscillate to give scratch pattern that is harder for the eye to discern. Sheet sanders typically just have some random oscillation. RO sanders can be more aggressive. Both sanders can support dust collection (see Festool), but typically sheet sanders do not have provisions for dust collection, and RO sanders almost always ...


3

The faster it spins, the more material it will remove. When sanding solid wood, I go full speed. But, if I am sanding a coat of poly or a plywood veneer, I go at it with a much slower speed as to not chew through the top layer of material.


3

do I really need to sand... before priming? Ideally yes. The role of sanding is not just about smoothing, it can also be about prepping a surface to properly accept a finish (or glue). Any older wood surface should be sanded lightly prior to applying glue to ensure a good bond and the same holds for when paint or varnish is applied. Just to be clear, you ...


3

Actual scorching of wood is possible with a belt sander running at a high enough speed and with the wood held tightly against the belt (particularly a problem with worn belts). That's the most obvious 'effect' resulting from speed that I can think of sanding wood itself and it's a flaw in sanding technique and not directly a fault of the sander. But other ...


2

In addition to the other comments: sanding produces heat. Depending on what you're doing, it may be possible to produce enough heat to affect the wood's color, "burning" the surface a bit. That's more likely with cutting tools, but a really aggressive sander could do it. But, yeah, mostly it's a matter of getting the job done quickly traded off against the ...


1

I think your option 1 is partly the way to go, take some of it out, shim underneath and reinstall. More info on this and how it's done in the following links. From our glorious DIY neighbour: How do I use 'surface shims' to level out a sloping floor? flattening subfloor with plywood! on the Floor Pro forums. How to Lay Subfloor on an Uneven Floor on SF Gate....


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