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#3 in a series of no-doubt blindingly obvious newbie questions

Cumpiano seems to default to scraping in a lot of cases and I was wondering why. Isn't a well-planed surface superior to a scraped one?

Thanks in advance

Steve

No, it's not superior. Even if someone is not sanding a surface, typically scraping follows planing, since planing can leave plane marks, which scraping removes.....and try planing the purflings and binding on a finished body.

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Isn't scraping essentially micro planing provided that one uses a good, sharp scraper?

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Ann Arbor Guitars

Planes tend to slice wood fibers and scrapers (even sharp, correctly prepared scrapers) tend to "burnish" the wood fibers. For that reason, planing is slightly preferred, where possible.

Thanks Steve C.!

Steve S you may be splitting fibers, er I mean hairs here with scraping being certainly good enough for our purposes. Good question though!

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Ann Arbor Guitars

I disagree that scrapers tend to burnish the wood. Only dull scrapers will do this. Typically, it happens when the tool is dragged backwards over the wood. This is bad technique, and will tend to dull scrapers and planes equally. A well-sharpened scraper cuts a shaving you can almost read through. File-sharpened scrapers have a little more aggressive edge. Honed scrapers will take an incredibly fine shaving, and leave a beautiful surface in their wake. In short, don't shy away from the scraper--you need it in addition to the plane.

I agree you need both. However, I actually have photos taken with a Scanning Electron Microscope of wood surfaces comparing plane-prepared surfaces and scraper-prepared surfaces. At that level of investigation, the difference between the two is quite clear. The plane leaves a very clean surface, and the scraper, properly sharpened, crushes some of the wood fibers/structure.

That's interesting. What does sandpaper do?

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Waddy

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Waddy, you are in luck, I have those, too. (But) it's been so long since I have looked at those, I don't remember my observations. I will take another look tonight when I get home from work. I think it would be safe to say, though, that a plane-prepared surface is the cleanest of all, and I think many agree that the depth and chatoyance attainable is maximized by hand planing. I will report back tonight.

Interesting topic,
I have gotten to where I only use finger planes for shaping the braces, other than I have little use for them.
Now my scrapers, there one of my most used tools.

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Lance@LuthiersForum.com

The question I am addressing is the surface left by scraping vs planing vs sanding (and machine planing) and not the time and place to use each.

A comparison from micrographs taken by Stephen Smulski with an SEM during graduate work in wood science at the Univ. of Massachusetts, Amherst (Taunton Press "Planes and Chisels"):

a) The cleanest surface comes from a well-tuned smoothing plane. Seen in the pictures are open vessel elements of various kinds, e.g., ray cells, etc. Most fibers are cleanly severed.

b) Machine planed maple still shows open vessel elements, but smaller features are obscured by torn and pounded fibers. Burnishing is evident.

c) Maple was worked with a scraper. Most of the wood vessels are filled in by torn and rolled tissue, and the surface is scratched by the minute raggedness of the scraper's edge.

d) Maple hand-sanded with 220-grit sandpaper (Norton open-coat garnet) is just about as clean as the scraped surface but with more scratches. Vessel elements are filled with wood dust rather than torn fibers.

To give the other side: FWW #180 has an article where separate mahogany boards were prepared respectively by scraping, planing and sanding. Whereas it was easy to tell how the boards were prepared, after finishing the boards, the judges could not tell which method was used. Maybe in the end, as far as finish quality is concerned, and perhaps depending on the finish material, any differences become moot.

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All due respect Steve but surely these results would depend entirely on who preped the scrapper and turned the burr. How fine did they go flattening the sides? What process did this person use to burnish the hook? What task did they have in mind when they prepared the scraper for his comparison? Was it in their mind to be removing material fast like a well honed plane does so well, or where they full aware that micro photography would be used to measure flatness of finish, something which a plane cannot do near so well as a scraper preped for this task. Who honed the plane? How skilled was each user with these hand tools which require totally different operational techniques?

You get the idea, the variables are vast, but at the end of the day when it comes to finishing wood to a smooth lustrous finish, give me a card scraper prepared for the task at hand any day. No dust or scratching that you get with abrasive paper, no tear, chatter or ridging you can get with a plane, just smooth cleanly cut wood shaved so fine that it shines.

Cheers

Kim

Good questions all, Kim.

In the end, the task at hand clearly dictates the tool to be used. I enjoy using all three, but for various reasons, sand as little as possible.

If we confine ourselves to 'sharp' planes and scrapers, then, as has been said, the scraper will tend to burnish more. Obvoiusly a dull scraper will make a mess, but so will a dull plane. We, of course, are all skilled practitioners who use only sharp tools....

The difference between a planed and scraped surface is greater on soft wood than hard. The scraper tends to compress the earlywood and cut the latewood. Over time the earlywood swells back up, leaving the latewood below the surface, and this shows up very strongly under finish as a 'corduroy' effect.

Sandpaper leaves scratches . As you go finer the scratches become smaller, until they are more or less the same size as the features of the wood structure itself. At that point it doesn't make much sense to go any finer, and the surface can be 'just as good' as you'd get with a plane or scraper. Again, none of US would use an old, ratty looking dull piece of sandpaper, now would we.....