Hi folks!
Long time (six months) lurker, first time poster.
I am an intermediate level woodworker, with most of my experience doing book shelves, entertainment centers, and other built in’s in most of the many houses we lived in during my thirty year Navy career. Now that I am retired, and don’t plan to move again, I am trying to take my woodworking skills to the next level.
I recently built my first ever woodworking bench following the design one of you linked me to at terraclavis.com/bws. The results were not bad. I did have one significant problem, however, in that one corner of the bench top warped up almost a half inch above the bench frame. Some of the 2×4’s on the top sat in my 9 percent relative humidity basement for over a week and some went immediately from the lumber yard to glue up. Anyway, after the top stabilized for a month or so I planed it flat and am living with the result.
For my next project, I want to build a new desk, most likely out of alder. I was going to build the top out of solid strips of 4/4 glued up, but my experience with the workbench has me worried that I’ll end up with a warped top.
So my question is, how do I go about making a warp free top? Let the wood sit in the house for weeks or months? How about gluing, say, 1/8″thick strips of alder onto a 3/4″ slab of MDF? Any thoughts from you all would be appreciated.
I have a band saw and planner, so re-sawing is something I can do.
Chris
Replies
Warping is caused by uneven expansion/contraction rates and the resultant pressures they cause in the wood.
Look at the end of a log. Drawing a straight line from the center out to the edge of the log is the radial direction. Drawing a curved line along an annual ring is the tangential direction.
These two directions have different expansion/contraction rates, with tangential generally being about double that of radial.
So, if you glue up a quarter sawn board to a flat sawn board, your asking for problems. Ideally, perfectly quarter sawn boards would be best. Since ideal is next to impossible, get as close to quarter sawn as you can, then when laying them out for glue up, alternate the direction of the grain from board to board.
Also, after the lumber is selected, plane it out, saw to approximate width leaving them about 6-8" longer than needed. Then lay them out flat and let them acclimate for a couple of weeks in your shop. Discard any that cup, bow, or warp in this period.
PlaneWood by Mike_in_Katy (maker of fine sawdust!)
PlaneWood
There are several ways to approach the glueup itself. You can orient all the boards either pith in or pith out. This gives a smooth arc as the wood moves and is easier to restrain.
You can alternate pith, sap, pith, etc., this will result in a slight washboard when the boards move or you can go for best grain match. I generally go for best grain match but arguements can be made for any of these techniques.
The key to success here is to restrain the top in such a way to allow for shrinkage and expansion and still hold the slab flat.
Lee
Thanks to both above.
When I built the work bench, I culled the least twisted and bowed two by's I could find. Culling out quarter sawn from flat sawn was not an option. Almost EVERY stick I looked at had the first year's growth in the middle of one edge with concentric rings going out from there. I chose to glue them up thusly: ()(). I'm trying to show four two by fours sistered. Hope that makes sense.
Now on to the desk. What do you folks think of gluing thin (1/8") boards to 3/4" plywood or MDF as a method of stabilizing the desk top?
Thanks
Chris
If you glue 1/8 inch strips to one side you will also need to do it to the other side, otherwise you may get significant warping. If you use solid wood as described by the previous posters you should be okay.
I have not used alder myself but I thought it was somewhat on the soft side so it may not be the most ideal wood for a desktop. Others may be able to give you better advice on this.
Chris,
I'm just trying my first veneer project with some nice cherry. I believe most would say an 1/8" is to thick...needs to be thinner or the veneer will split (maybe I'm wrong). However there are some other issues like jointing and sanding the veneer...too thin for the planer so removing the marks is all by hand...both sides...and holding the stock down is a pain. I'll probably joint with a straight edge and a knife.
I've had some good luck lately buying 16/4 by 6" chunks of wood ...which is usually sold as a cutoff and, therefore, a discount. I quarter saw these and sticker for a couple of weeks. So far the maple and ash have stayed quite flat(2-3 months).
> What do you folks think of gluing thin (1/8") boards to 3/4" plywood or MDF as a method of stabilizing the desk top <
Don't do it mate! Gluing solid wood to an inflexible substrate is asking for trouble. The wood will try to move, the MDF will try to stop it, and one or the other will lose the battle.
If the solid wood sits in your workspace for a few weeks before glue-up and dosn't move, it'll probably be ok. Wide thin boards are riskier than narrow thick boards. If there are any boards that look as tho they might be inclined to move, position them in the middle of your glued-up panel.
Bread-board ends may be a solution (as long as you engineer them to allow the bench top to move with changes in humidity). Ensure the top is well fastened to the base.
Good luck
MalcolmNew Zealand | New Thinking
Well, the MDF is anything but inflexible but trust the Kiwi man on this, Plywood or MDf are not your solution.LeeMontanaFest
And I've got the photographs to prove it!
An early and hard-won lesson
MalcolmNew Zealand | New Thinking
Thanks all. I'll dump the wood on MDF idea. Y'all convinced me that I can make the top out of solid wood if I take proper precations, which I will.
Chris
Just me so... Probably no good advice.. But..
I made a workbench for a friend about three years ago.. He loves it.. I used two sheets of MDF 3/4" glued together with hard maple flooring glued to it.. 3/4" unfinished flooring on sale... The type without relive so it has flat edges.. Cost was the reason.. It is FLAT and has no warping.. It is out in a unheated garage..
Nice bench if I don't say so myself.. Just hard to move HEAVY...
I forgot.. The glue is a two part.. I forgot the brand but for building boats and is waterproof.. I see no wood movement...
Edited 4/14/2005 12:56 pm ET by Will George
Interesting.
I'm thinking that if I ever replace the bench top, I'll do it with an MDF torsion box. I've made several shop tables using this technique in the past. Heavy, yes but perfectly flat.
Chris
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