Sanding -- why do they do that to me? :-)

Hi,
I'm kind of curious about the benefits of sanding. Plus, I'm extra confused by the long list of choices for the type of sander (handheld, random orbital, belt, finish sanders, etc -- what the hell is that? aren't all the others I mentioned intended as finishing tools?)
So, it makes me wonder: why does a surface that has been extra smoothed with a properly-sharp hand plane, or even a flush router bit, etc., need sanding? Those things get a mirror-look flatness that makes me wonder why would I want to pass a sanding machine on it.
Another thing is: I guess sanding should be the very last step -- am I understanding correctly assuming that it should be done *after* assembling all the pieces? If so, what about concave corners? (i.e., when one has to sand the inside of a right-angle)
I'll be most grateful for any tips you may offer to a complete beginner -- so far I've been learning and getting more confident with *building* the furniture piece (working all the pieces, joints, improving my skills with the tools, etc.). But right now I'm near the end of my first project, and it's completely assembled, only missing the finishing details.
Any advice on what tools to look for would be also appreciated.
Thanks,
Carlos --
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Finish sanding to just prior to a finish, or between coats of finish

Good compromise of minimal scratch patter and agressiveness.

NOT a finishing tool. Belt sanders are for removing material (shaping not smoothing).

See handheld.
> sanders, etc -- what the hell is that? aren't all the

No belt sander.

It doesn't.

Maybe. It depends on the surface left by the prior step of machining. A power planer seldom leaves a surface which is ready for a finish. This should be followed by either sanding scraping or smoothing with a handplane.

You get it. There is no need if the prior machining (power or hand) step leaves a surface that is good enough. There is no magic to sanding that you are missing.
Also, understand that flat and smooth are not the same thing. Sanding *can* help with both of these.

No necessarily. But be careful, if you sand before assembling, you can round over acorner which is supposed to be flush with the adjoining part. It will look wrong if you do.

This is a good place to sand before assembly.

Or don't sand. There are alternatives such as using a card scraper for final preparation of a surface. A plane or a well-tuned scraper will slice the wood at cellular boundries, or at least cut cleanly. Sanding grinds the surface and will generally leave a less chatoyance.
-Steve
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On Mon, 06 Dec 2004 12:44:59 -0500, Carlos Moreno

There's no benefit to sanding a piece which has been smooth-planed.
My spokeshave work still needs a bit of sanding. :)
Sanding is FAST and doesn't require much skill and can be done quickly by powerful machines in a commercial mass production shop.
Planing takes a bit of practice, but produces a finish that brings me to tears once I'm in the planing zone.
Router profiles don't usually need much sanding, but sometimes do, depending on how sharp your bit is.
If you're doing handwork on solid wood, plane, spokeshave and breathe easy.
If you're doing kitchen-sized runs of cabinet carcases, you'll probably consider some kind of sanding apparatus.
Hand sanding is easy and doesn't raise scads of dust, but is slow.
Palm sanders are faster, but dusty. You'll want a downdraft table or nice weather so you can work outside.
A random-orbit sander is faster and dustier.
A belt sander is fastest and dustiest of all, but requires a bit of practice not to mung things.
Beyond that, you get into oscillating spindle sanders, drum sanders, belt sanders which all have their niche. The only "Gee I wish I . . " sanding machines for me are a 6x48 belt sander and a skinny sander for knife grinding. Others might tell you that you need a triple drum sander that can do a 48" wide table in a single pass . . .
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U-CDK_CHARLES\Charles wrote:

This reminded me of an old joke...
- *sigh* I wish I had the money to buy a triple 48" drum sander...
- What do you need that drum sander for?
- I need the 30 thousand dollars, not the sander!!
;-)
Carlos -- PS: Thanks for all the tips and info!
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Sanding after assembly ensures adjacent surfaces are truly flush with one another. Sand difficult to reach surfaces before assembly, also. I tend to plane, sand, assemble, sand, wet to raise grain, sand with 400 LIGHTLY, dye, seal, sand, topcoat, sand, topcoat, sand, topcoat.
David
Carlos Moreno wrote:

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Just tilt the blade and run the stock through flat. That is unless you get some interference between the dado blade and some part of your saw. It should be doable.
-j

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