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Thread: Look at your workbenches!

  1. #1
    Join Date
    Feb 2007
    Location
    Between St Joseph and Savannah, MO
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    147

    Look at your workbenches!

    I want to share the following with you, because it happened to me.

    I heat the shop during Winter, using a forced air system. This creates a very dry heat that could result in bench tops not being as flat as we might need them. The following photos illustrate the current status of my workbench top - the total gap in the top photo is 1/8-inch, with the precision straight edge held flat on the back edge of the bench:

    The bench top:


    The end cap:

    Of course, the dry air is likely to also affect everything else wood in the shop, such as your lumber and, by extension, any projects you are currently working on.

    I recently bought a monitoring system, which will allow me to monitor the relative humidity in my shop using an inexpensive hygrometer that also monitors temperature. I believe I will be able to start using a humidifier when needed, to attempt to keep the humidity in the shop fairly constant.

    You will find additional details and comments at my blog.


    .
    Al
    Watch videos from Woodworking in America in Berea, KY
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  2. #2
    Join Date
    Oct 2006
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    The Heart of Dixie
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    My question is why did it bow? I would expect it to expand but not bow. First thought/question is was the top was tied down, tried to expanded it couldn't and had to bow? No wait...... if it's dry it should shrink, not expand. This doesn't make sense.

    I would like to know why it happened so I can design one that will allow for whatever caused that.
    God grant me the senility to forget the people I never liked anyway,
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  3. #3
    Join Date
    Nov 2006
    Location
    Oak Harbor Washington on Whidbey Island
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    My bench top is the same as ever. 1" plywood sub straight, 3/4" high density chip board & 1/4" tempered Masonite replaceable top wrapped in Poplar & it seems to stay fairly flat.

    I know this doesn't take away the disappointment of those that spent so much time, money & effort to make such a beautiful bench only to have this happen.

    I hope you can get this problem figured out.
    "Forget the flat stuff slap something on the spinny thing and lets go, we're burning daylight" Bart Leetch
    "If it ain't round you may be a knuckle dragger""Turners drag their nuckles too, they just do it at a higher RPM"Bart

  4. #4
    Join Date
    Feb 2008
    Location
    Fort Washington, PA
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    Quote Originally Posted by Al Navas View Post
    ...I heat the shop during Winter, using a forced air system. This creates a very dry heat that could result in bench tops not being as flat as we might need them...

    Al I too suffer from the dry forced air heat that heats my shop. In my case it's usually prepared stock. In winter, if I take a board from rough to S4S and don't use it right away, the next day it will often be a tad off. This even if that rough board has been sitting in the shop getting used to the indoors for several weeks. It's something I just have learned to live with and work around. Thus one of the best investments I've made has been my Wagner pinless moisture meter... one of those tools that after you get it and start using (relying on) it you wonder how you got along without it.

    As for flat workbench... I assemble drawers etc on a 500 lb monster I built that is topped with 1 inch thick steel plate, covered with some hardboard. So it's always dead flat. Found the large steel plates under a RR bridge in a river, they were apparently spacers used in building the bridge. I managed to lug two of them home (200lb a pop) and built a table under two of them side by side. The table is thus so heavy it can't be easily moved, so I put some heavy duty wheels on it that came from one of those big metal trash containers.
    Build it Break it Fix it ...repeat

  5. #5
    Join Date
    Feb 2007
    Location
    Between St Joseph and Savannah, MO
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    Quote Originally Posted by Jeff Horton View Post
    My question is why did it bow? ...

    I would like to know why it happened so I can design one that will allow for whatever caused that.
    It happened due to moisture loss during the heating season. One just has to do one of two things: Either install some sort of system to add moisture to the shop, or plan on routinely flattening the bench top once per year.

    It became critical this year, not because I started using hand tools, but because I just started using a vacuum press and I need a perfectly flat surface to be able to press flat veneered panels.




    Quote Originally Posted by Bart Leetch View Post
    My bench top is the same as ever. 1" plywood sub straight, 3/4" high density chip board & 1/4" tempered Masonite replaceable top wrapped in Poplar & it seems to stay fairly flat. ...

    ...I hope you can get this problem figured out.
    You have a system that is pretty much impervious to relative humidity changes, Bart! I think I have it worked out, but I must monitor to determine how large the swings are. Then I will be able to decide on a system to install.





    Quote Originally Posted by John Downey View Post
    Not at all un-usual, bench tops are intended to be dressed now and then. I'd expect that over the course of several years of bowing back and fourth and re-flattening, the bow will become less pronounced each time. Get out a jointer plane (or pick one up if you don't already own one) and spend a morning re-flattening it.
    I have started sharpening the large #8, John. I will wait until late April to early May, as the heating season will have ended by then and the top should be a little more stable. I don't want to start too soon, and then have a low spot . I have also noted it, and added to the yearly machine maintenance schedule.





    Quote Originally Posted by Dave Kauffman View Post
    ...Thus one of the best investments I've made has been my Wagner pinless moisture meter... one of those tools that after you get it and start using (relying on) it you wonder how you got along without it.

    As for flat workbench... I assemble drawers etc on a 500 lb monster I built that is topped with 1 inch thick steel plate, covered with some hardboard. So it's always dead flat. Found the large steel plates under a RR bridge in a river, they were apparently spacers used in building the bridge. I managed to lug two of them home (200lb a pop) and built a table under two of them side by side. The table is thus so heavy it can't be easily moved, so I put some heavy duty wheels on it that came from one of those big metal trash containers.
    Dave,
    My Wagner unit is now about 12 years old, and a great tool! Highly recommended. That is indeed a monster assembly table - I would love to see some photos, if possible.


    Thank you all for your feedback!


    .
    Al
    Watch videos from Woodworking in America in Berea, KY
    New blog URL: http://sandal-woodsblog.com/
    Sandal Woods - Fine Woodworking
    We will build your heirlooms

  6. #6
    Join Date
    Apr 2007
    Location
    Decatur, Illinois
    Posts
    177
    could it be the top was sealed and the bottom of the top deck was not sealed? the bottom lost more moisture than the top and shrank more???

    mine is three layers of baltic birch plywood with a 1/4" hardboard top..seems to be staying flat.
    99% of lawyers give the rest a bad name...Steven Wright.

  7. #7
    Join Date
    Feb 2007
    Location
    Between St Joseph and Savannah, MO
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    147
    Clark,

    These benches are typically not sealed anywhere. Only a little oil is applied, as you want them to breathe.

    After a lot of thought and analysis by several people, it was moisture loss due to heating that caused the high spot along the full length of the bench. In addition, the beech used to make the bench could have been wetter that it should have been. The lumber used is European beech, possibly quarter-sawn, from the looks of the few exposed boards I can see. Although the QS lumber is the most stable, it can still change cross-grain dimensions when the relative humidity changes. But it is not normal for properly dried lumber to change this much. The boards are on edge, in the vertical direction; this means that most of the changes, if any, will be in the vertical direction.

    It never was an issue, until I needed a perfectly flat surface. I am sure that hand tool users would have found this problem a long time ago.


    .
    Al
    Watch videos from Woodworking in America in Berea, KY
    New blog URL: http://sandal-woodsblog.com/
    Sandal Woods - Fine Woodworking
    We will build your heirlooms

  8. #8
    Join Date
    Feb 2008
    Location
    Fort Washington, PA
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    180
    Quote Originally Posted by Al Navas View Post
    ...Dave, My Wagner unit is now about 12 years old, and a great tool! Highly recommended. That is indeed a monster assembly table - I would love to see some photos, if possible.
    OK Al, but it ain't pretty, and it's not that large, but it sure is functional and unless the temperature gets up to where steel melts, it is always dead flat. The contraption you see under the table is my crude design for raising the table legs up off the floor an inch so I can roll the thing (it's over 500lbs), then set it down on it's legs again. Even given the weight of the steel plate, I might have over-engineered the base. I sistered a couple of 2x10's so each rail is basically a 3 inch by 9 1/2 inch timber, with 4x4 legs. I wanted something so sturdy that nothing I could do to anything on or clamped to the table top would budge the table. I did succeed in doing that. Go easy on my design to temporarily raise the table off the floor. I built this over 20 years ago and would I be doing it today, I'd have engineered a more elegant, less "Flintstone" way of making the table mobile. The vice at the one end has osage orange jaws, and came from an old inner city school woodshop in the 50's.

    table with (well worn) hardboard cover over the plate steel


    table showing the two pieces of 1" thick plate steel top


    the plate steel edges are strait but a bit crude, the plate itself however is dead flat
    Build it Break it Fix it ...repeat

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