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David Gendron
04-29-2009, 12:30 PM
I was just wondering what you guys are thinking when working wood, Of how flat is flat? I just flatened my banch top and started to think of that, cause when I was done, I put the "straight"edge to the top and with a raking light, I could see a tin line of light in some place, that look like less than 1/32...
I was just wondering???
David

Scott Loven
04-29-2009, 12:46 PM
How flat is your straight edge? How long? 1/32" ( .03125 ) would be ok with me for the work I do.

Scott

David Keller NC
04-29-2009, 12:51 PM
David - An important question with no absolute answer. Here's my take:

Be careful in interpreting the "sliver of light" underneath a straightedge. Depending on how thick the straightedge is and the lighting, that can be as little as 1/2 of a thousandth of an inch.

On a bench, the need for "flat" differs from whether you're talking about the length or the width. It is considerably more important to have the width flat (say within 20 - 60 thousandths over the bench's width) than it is to have the length flat. The reason has to do with the way you use a bench to flatten boards.

If your bench is out of flat 1/8" over its entire length of, say, 8 feet (that's easily acheivable with hand planes, BTW), then a board that you're 4-squaring may be out of flat by the same amount. That's usually no big deal in a piece of furniture - the length of board is very flexible, and an average furniture sized part is going to be 4' long, max. And getting a 4' long piece of wood to flex 1/16" inch is absolutely no big deal when it comes time to glue up.

However, this is not true over the width of a piece of wood. Generally speaking, a drawer side that is slightly bowed over its length (and I do mean slightly, not egregiously) isn't a problem, but it can be a nightmare to accurately cut dovetails and assemble it if it's cupped over its width by more than a 32nd or so.

Jim Koepke
04-29-2009, 12:55 PM
Surely, there will be a wide variety of opinions on this.

Let me be the first to say this is unacceptable and you should crate it up and ship it to me and build a new one for your self.:D

A perfectly flat surface would be nice, but is it achievable? One does not want to have a significant bow in the surface as this could be transfered to anything that one tried to flatten on such a surface.

So it comes down to the work you will be doing on the bench. If you are trying to make 1/4 inch thick panels, the 1/32 spot may cause problems. If you are making cabinets and book shelves, it is not as likely to be a cause for concern.

Just my 2¢, lets see what others say.

jim

Luke Townsley
04-29-2009, 1:55 PM
I would say that 1/32 for an 8' bench is in the right ballpark depending on the work you do and where the bench is off. If you have an 8' bench that isn't out more than +/- 1/32 in any direction, I would say that you are borderline good assuming that it is fairly gradual and not ocean wave like.

If you mean +/- 1/64, that would allow you up to 1/32" of variance and would be much better and probably good enough for just about anybody, again depending on what you are doing and where it is out.

Personally, I like to have my bench flat enough along its length so I don't have to use a straightedge when edge jointing. I can just blow off the shavings, set it on the bench, and see if it is out.

I have about 4 square inches on one corner of my bench that is measurably low (I forget now, but let's say about 1/32"), but it doesn't matter because it is on the back and I never do anything requiring flatness on that spot.

Also, when you flatten a new bench, especially in Southern Yellow Pine or wood that is not well seasoned and adjusted to your shop, it doesn't hurt to sneak up on it and let it set a few days between the final passes. If you are close enough to get to work now, just put a coat of something on the top (or don't) and go to work. You can take another pass or two 6 months from now.

I very carefully flattened my 6' bench with a jack plane last fall and haven't felt the need to flatten it again even after I bought a nice jointer plane. It is just good enough.

Don C Peterson
04-29-2009, 2:10 PM
"Flatness" or any other kind of absolute exactness when dealing with wood is something that just cannot be achieved. 1/32" variation over the length of the bench is very flat and should be more than flat enough for any kind of woodworking IMO.

David Gendron
04-29-2009, 10:20 PM
Don, That's what I wanted to hear! not that I was looking for some sort of answers, but just wantet to know what was other people tought on the mathers!

My banche before flatening was kind of flat and I manage to built some nicely done( I think they are!) funitures on that banche and didn't have any problems flatening large and small pieces. In my shop, it's only hand tools(no power at all other than light and radio...) and that banche was my first big project and it's full of mistakes that the Shwarz wouldn't approuve and for others would finish in the scap pile!!
the only reason I reflatened it is because I had to reglue one of the lamination of the top.

As for flatness, are people going over board with that? And is it realy important to achive granit plate flatness in woodworking? Is it even importent to pass more time tuning up tools than working with them? where is all that going? Shavings that are so tin that you are using your smoothing plane more than your Jack plane! Isn't it the idea to as tick a shaving possible without tear out?

anyway, it's interesting to see what people have to say about it, so keep comenting, I like it!!

Luke Townsley
04-29-2009, 11:24 PM
I don't think there is an issue with going overboard on bench flattening as there might be with honing blades. Honing blades can be problematic because it is an event that is repeated with a high frequency sometimes multiple times in a single working session.

Flattening a bench is relatively fast, easy to do (assuming it is already pretty flat), and long lasting.

That said, granite plate flatness is not possible on a wooden bench. Wood moves and will keep moving. Just go over it carefully with a few passes with a jointer plane and you are done with it.

If you don't like it, use it for a while, and you will either get comfortable with it, or your skills will improve and you can get it flatter if your top is stable enough to be made flatter.

A lot of people take a pass with a plane every year or so anyway to clean up the bench and remove any wear patterns.

David Keller NC
04-30-2009, 9:29 AM
"As for flatness, are people going over board with that? And is it realy important to achive granit plate flatness in woodworking? Is it even importent to pass more time tuning up tools than working with them? where is all that going? Shavings that are so tin that you are using your smoothing plane more than your Jack plane! Isn't it the idea to as tick a shaving possible without tear out?"

David - I think you're beginning to see the major flaw in thinking that all of us that started out with power tools had. That is, building furniture with the expectation of interchangeable parts and machinist's precision.

That's absolutely critical in a factory operation, and absolutely foolish for a one-off, one-man operation (or even a small production run in a small shop). There's a lot of reasons for this, but one of them is that interchangeable parts is huge waste of time, particularly when hand tools are available and the user's skilled in using them.

It is true that a miter plane and a shooting board can get several rails with tenons to an exactness of length that cannot be matched with a table saw and a cross-cut jig, but it's not necessary and not beneficial in building, for example - a corner cabinet. What one wants is to hand-fit each joint such that it closes tight and looks nice, irrespective of whether you can fit the top rail in the bottom's position.

Otherwise, you can spend all day making those rails interchangeable instead of 15 minutes making rail "A" fit in mortises "B" and "C".

It's the same with 4-squaring a board - the most efficient way to do it is with a roughing plane, winding sticks and a marking gauge, regardless of tear-out. One only worries about tear-out when and if one of the sides of the board will be a show surface with a finish on it.

Sean Hughto
04-30-2009, 10:06 AM
Very well put.

Richard Dooling
04-30-2009, 11:25 AM
David - I think you're beginning to see the major flaw in thinking that all of us that started out with power tools had. That is, building furniture with the expectation of interchangeable parts and machinist's precision.

Otherwise, you can spend all day making those rails interchangeable instead of 15 minutes making rail "A" fit in mortises "B" and "C".

It's the same with 4-squaring a board - the most efficient way to do it is with a roughing plane, winding sticks and a marking gauge, regardless of tear-out. One only worries about tear-out when and if one of the sides of the board will be a show surface with a finish on it.

Amen! I came out of a power tool shop and though I never thought of it this way you're right. I've been striving for identical, interchangeable parts. I use a blended approach of power tools and, increasingly, hand tools now. Band sawing and rasping some forms has started me seeing that there is close enough – visually and mechanically.

I've been coming to this realization that parts can be made to reasonable tolerances and do not need to be absolutely identical.

You have hit the nail on my head!

.

Don C Peterson
04-30-2009, 11:51 AM
Amen! I came out of a power tool shop and though I never thought of it this way you're right. I've been striving for identical, interchangeable parts. I use a blended approach of power tools and, increasingly, hand tools now. Band sawing and rasping some forms has started me seeing that there is close enough – visually and mechanically.

I've been coming to this realization that parts can be made to reasonable tolerances and do not need to be absolutely identical.

You have hit the nail on my head!

.
Ouch! That's gotta hurt, but progress quite often is painful...

David Gendron
04-30-2009, 12:18 PM
I like what I read... Keep it going!;)

Luke Townsley
05-01-2009, 11:57 AM
I agree about factory perfectness in hand tool woodworking. Therein lies a conundrum.

We can spend untold hours and skill to produce something that can be factory made with more precision and cheaper than what we do.

We feel the need to compete, but it is sort of like the homely homemaker trying to compete with the photoshopped magazine supermodel. On the other hand, men don't generally stay marry and stay married to supermodels. They do stay married to "good women".

Our projects take on their own character and have an internal strength that others might not readily appreciate, but that will stand the test of time.

David Gendron
05-01-2009, 12:04 PM
Well said Luke.

Sean Hughto
05-01-2009, 12:19 PM
Luke, I think you have it backwards. If I wanted to make something that looked like an Ikea table in my home shop, I'm confident that I could. Indeed, it would be relatively easy using power tools, and only moderately harder using hand tools. But Ikea could NEVER make something like I can make with handtools. I don't strive for factory "perfection" - it would be like striving to make a McDonald's hamburger at home. Why would you? You can use ground silrloin, your own charcoal grill, your own homegrown tomatoes fresh from the garden, your own rolls, freshly baked, your pickles you canned yourself, etc. Which would you rather eat? Here's my present project in progress:

http://farm4.static.flickr.com/3332/3475337558_334e4d4b0d.jpg

Let me know if you ever see a cabinet like that at Ikea or Ethan Allen.

michael osadchuk
05-02-2009, 4:08 PM
...a benchtop can be a very quick measuring tool for flatness so if you have the means - laminated benchtop construction, a few good planes and some winding sticks - why would you choose to deprieve yourself of that assistance .... this doesn't mean that every single square foot of benchtop has to be brought in the flattness with the rest of the bench but for those areas of the benchtop that you know are flat it's a simple matter as Luke and David have area said to put the edge of a long board or face of panel against benchtop and if there no rocking or raking light showing, bingo, the pieces are flat.....

good luck

michael