Flat Out Flat - Possible?

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Hello:
I have struggled to a point way beyond frustration to get a surface- any surface dead-on flat. I have used the marking the high points method and used every plane scrub, jack, jointer, smooth, scraper, etc., No matter what I do I can't get it 100% flat. When I shine a light behind my Starrett, it is always off by a few thou. Is there a way to get a surface truly flat using hand planes and a scraper? It almost seems impossible. What am I doing wrong?
Thanks!
Bob
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Bob wrote:>Hello:

It could very well be impossible. Something I'm guilty of quite a lot, is worrying too much. What are you creating that you need so flat? Wood moves, and a "few thou" seems pretty darn good to me, especially with "cordless" tools. Tom Work at your leisure!
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Yes... a DJ-20 (which is NOT a hand plane) and throw that flashlight away...
You aren't building a nuclear reactor out of wood.
Bob wrote:
No matter what I do I can't get it 100% flat. When I shine a

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wrote:

Do you know where I can get plans for that - preferably free, since it is getting expensive to be fighting the infidels in so many places around the world? (Yes, I've already googled.) -- Osama
Oh yeh - Death to America!
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Osama wrote:

Shouldn't have threatened the Pakis you twit.
--
--John
Reply to jclarke at ae tee tee global dot net
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Bob wrote:

What am I doing wrong?

striving for perfection. do you REALLY need a piece of wood to be "dead flat", Bob?
dave
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snipped-for-privacy@operamail.com (Bob) wrote in

What you are doing wrong is expecting wood to be something God didn't make it to be. It isn't metal, or stone, or glass, or plastic.
Thank God.
Patriarch
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Bob,
Others have addressed the wood being flat issue for you but since you said "When I shine a light behind my Starrett, it is always off by a few thou.", it in-fact could be your Starett. The typical straight-edge is only guaranteed to .002 in 12" in. So how much do you really think you're off?
Bob S.

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picky, picky, picky..................

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Light behind a straightedge is deceiving. You can easily see .0001.

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On Tue, 06 Jul 2004 17:34:34 -0700, CW wrote:

Move the decimal point (.001") and I'm with you on this. The guy could also make the wood flat the same way a machinist would make an iron surface plate flat. He couldn't hold the same tolerances, but he -could- hold those tolerances that are appropriate for wood. (from high school geometry "Two lines, each parallel to a third line, are also parallel to each other.") A flat is simply a line expressed as radiating from a central point on a plane. He could finish the surface of three pieces of material of approximately the same size and sand them smooth, then apply die-makers "spotting blue" to one of the pieces, rub it against another and then cut off the high spots. Lather, rinse, repeat until all three pieces have a uniform pattern of high spots.
It's a senseless exercise in wasted time, but it would keep him out of trouble for a few days.
--
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http://organic-earth.com (organic gardening)
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Using a straight edge.
You get better results if you just run your hand across it. If it feels flat, it is flat. Another method is to take the piece into the house and ask your wife "how does this look?" If she says "good", you are done.
Simplify your life. Nothing is perfect. Accept it. Ed snipped-for-privacy@snet.net http://pages.cthome.net/edhome
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Would you use this standard for two "flat" surfaces you are trying to join together? The OP has a good point, how close is close-enough for joining two edges? Sure, you can force two pieces together, but at what point is one trying to make the glued surface do too much?

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I can empathize with you. And sometimes it is interesting to do something just for the challenge of it, if no other reason. So go for it, and you will learn a lot. A couple of questions.
First, do you have a reference surface that is flat? Usually a granite block, these things cost significant $$ but are the real reference in machine shops where a "flat" surface is required. Without that reference, your straightedge is probably off by more than your desired flatness, unless you have some specialized tools.
Second, what is the ratio between the area you are trying to flatten and the thickness of the piece? Keep in mind **everything** bends -- it's just a matter of degree how much. Unless the ratio less than about 3 (three times as long as the piece is thick) you shouldn't expect to hold a surface flat. How do you judge the flatness of a peice of cardboard? It bend when you pick it up. Look at the backing of optical mirrors -- they are not just left to flex as they wish.
Third, how big is the flat surface? If you want a area of more than (say) 6x6 inches, in wood, good luck. If it is 2x2 inches, you will have better chances. In big pieces of wood, the material rigidity and stability just are not in favor of your success. Stuff that can be made flat -- and stay flat -- is usually stiff and brittle: not the description one would apply to wood. This is why flat surfaces on machines are often cast iron, not steel.
Keep us posted.
Matthew

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On Tue, 6 Jul 2004 20:53:45 -0500, "Matthew"
......and in reply I say!:
remove ns from my header address to reply via email
Nice answer. You have, I think, been trolled.

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snipped-for-privacy@operamail.com (Bob) wrote in message

Assuming this isn't a troll: A few thou is perfectly adequate for most things, and wood moves, so even if you got what you thought was a perfectly flat surface today, by tomorrow it could be off.
I do all my thicknessing by hand too, and I've finally come to the conclusion that what really matters is that the area where the wood will be joined. E.g., if you're going to be joining pieces with dovetails, make sure that your ends are flat and of uniform thickness, but don't sweat it if the center of the board is off by a tiny bit.
If you're surfacing a board for a tabletop, you want to make sure that the contact points where it will rest on the base are uniform, but having it be a bit off in the center probably won't matter (especially on the bottom).
FWIW, as far as technique goes: I usually start with a piece that is slightly oversize and use either a foreplane, jointer or low-angle jack with a toothing iron and approach the board at an angle (roughly 45 degrees). I plane across from one direction until I've covered the whole board with plane tracks and then reverse and go from the other direction until I've removed all of the first marks. (I also check with a straightedge or winding sticks to make sure I'm not dealing with a twisted board.)
Then I come back with a smoother and go with the grain until I've gotten rid of all of the previous marks. Usually by then the board is pretty close to flat and all it takes is a bit of tweaking. (Again, if the board is twisted it takes a bit more work, but usually the initial planing with the jointer will get it pretty close if you check it with the winding sticks as you go.)
Most of all, don't stress over it. This is supposed to be fun. If you're not having any luck getting a board flat, give it a rest and go sharpen your plane irons or clean up your shop. Take a break from it, or you may just wind up making the situation worse. DAMHIKT.
Chuck Vance
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Chuck, Have you ever thickness planed a piece of Sapele?

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Lowell Holmes wrote:

Is that a trick question, Lowell? :-)
To the best of my knowledge, I've never planed any sapele at all. I have thickness planed cocobolo, yellowheart, purpleheart and various other quilted and figured woods. It's not something I enjoy, but I do it if I have to.
So what's sapele like?
Chuck Vance
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It is a mahogany type wood from Africa that has ribbon stripe grain that is interlocked and reverse. P van Rijckevorsel revealed that It plains well cross grain, but not with the grain. If your interested, check out the string *Sapele confusion*.
It is not a trick question. I think it is a gorgeous wood and have a project in mind using it. I bought a board and will make a box or table in order to learn how to work it.

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I had seen the thread title and passed it by. I'll check it out, thanks.

I'll have to do a Google search and see if I can find some pics of it. So I wonder how the stuff scrapes? Seems like you could always fall back on that if necessary.
Chuck Vance
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