I’m building two night stands, using mortise and tenon joinery. I have glued and assembled the sides, all of which I was able to get perfectly square. When I attempt to dry fit the sides together, I can’t get the complete assembly to come out square. It’s driving me nuts. The closest I got was a 1/8″ difference, top corner to top corner. I’d be fine with just gluing it up a little off kilter, but I intend to add a drawer and I worry it will either (a) not look square in its housing, or (b) not open and close smoothly if at all, or (c) both (a) and (b).
If this description isn’t clear enough, I have two pictures posted: the first is of the various pieces, square and ready for assembly. The second is of a dry fit with clamps, out of square and causing me loss of sleep. Before anyone suggests it, I have clamped a spacer in the open area at the top front — it doesn’t make a difference.
Any suggestions you might have are most welcome.
Edited 12/2/2009 11:54 pm ET by adirhu
Replies
If you place the two sides together, one over the other like mirror images, are they exactly the same or are they slightly off? Just one thing to check. Another would be to check to see if the legs are all absolutely parallel.
You'll get more suggestions in the morning.
Good luck,
Jim
adirhu,
I think every piece I have made has had a little war story associated with getting it square. Usually my problems are in the straightness or excessive tightness of the joinery, causing the rails to pitch, or sometimes it using those pony clamps.
I use a single runner sled with a fence on top of the table saw to do my glue ups. The piece is glued up upside down and clamped to both fences; the sled and TS. This can help with problem diagnosis and insures squareness at glue up.
Beware of Squareness Neurosis which is further complicated by over thinking the whole thing.
So they can all line up and shoot me first thing in the morning, but I must tell you that if all things come out geometrically dead square in woodworking it is more by good fortune than divine skill. Things that look square are found to be out if carefully measured, and things carefully measured and deemed square have a knack of looking "out"....
Remember that wood is flexible and compressible so a few extra tweaks on the clamps can make differences here and there and you soon become convinced that all is square-or otherwise ☺
I advise you to check for matching shoulder lengths, squareness of meeting ends, dimensions of pairs and so on, to be sure that you haven't made any arithmetical type mistakes, and then do the glue up.
And drawers are supposed to conform to the shape of the carcass , not the other way round
Adir,
Before they shoot Philip in the morning, I will have died a thousand deaths. If you're sure it isn't a measuring slip-up, then glue it up and skew the clamps a bit for persuasion as needed. All will be forgotten by evening.
David Ring
http://www.touchwood.co.il/?lang=e&id=1
If at all possible, reduce the size of your images, as we can only view about 20% of either image at a time.
That said, if something cannot go square, then a measurement in length or width or placement of a joint is off.
Denny
Denny , Try right clicking image and open in new window.
Tom
Thanks to all of you for the helpful pointers (and Toda Raba to David Ring). My best guess, since this is my first project using mortise and tenon joinery, is that I'm a bit off in their placement and that's what's going on. I especially appreciate your support in not overthinking this, and the implicit permission to take another clamp on the diagonal and bring it into square with a few twists of the dial. Them's my kind of woodworkers!
I'll try that. Thank you.
Denny
adirhu,
A couple of thoughts, going by your description. (I am on dialup, and photos that size will take 3 days to download.)
It is usually possible to shift your clamps so that they are pulling towards the longer diagonal, rather than straight along the sides, and so coax the frame square. Pull one end, or jaw, of the clamp out, away from the face of the frame, and do the same, but to the other jaw, to the opposing clamp.
Alternately, you might just put a clamp diagonally across the top of the frame and pull it just a bit past "just right".
In addition to the other areas to look for as a reason for your problem (unequal length aprons, out of square ends, uneven shoulders on tenons):
If the legs have been glued to the first set of aprons with uneven clamp pressure, it is possible that the legs are cocked on the ends of those aprons. This can happen when the clamp's jaws are extended past a line extended from the ends of the aprons, and the pressure causes the leg to "rock" just a bit instead of being pulled evenly against the tenon shoulders. Then when you do a final assembly, things are out of parallel, and can be a problem to get squared up.
Ray
I've had the same problem with mortised assemblies, and found that it was caused by slight offsets in the positions of tenons and mortises. So, even if the frame pieces are right, you can end up having the joints themselves pulling things out of square.
As others have said, slight un-squareness can be pulled into shape by clamp positioning, etc, and should not result in any real problems.
My money is on rdesigns to win.
Nice, tight-fitting M+T joints can send you down this path in a hurry. 1/4 degree over 18" means 3/32" off square. On one joint. Double it and your at 3/16" diagonal.
Look closely at the offending (opposite) joints - my first guess would be on the "long" diagonal dimension. See if you can tell where it bottoms out - the shoulders or the tenons? Recognize that no one will ever see the inside of the joint, so where the shoulder hits the mortised piece, a small gap inside the table will only be known by you, and you will forget about it in roughly 13 years.
I'll join Phillip and David and recommend that you don't overthink this issue. This is WOODworking - not tool and die machining. The tools, equipment, and techniques we use do quite well for the medium we work in, but drive machinests totally bananas.
A friend of mine is a retired CEO with a machine shop that most machinests would die for. I've seen him spend several hours fussing with dial indicators and calipers teasing a 0.0001" error out of something he's making. We once calculated that a simple bracket he made would have cost over $1000 if he were trying to recover it's real cost.
For 90+% of my work, your 1/8" out of square would be just fine. Except for my CEO friend, nobody else will ever notice something like that.
If the pieces are square, and the M&Ts are square, two things that can cause an out-of-square condition at glue-up are an out of level surface (floor or table) where you are assembling the piece or uneven clamp pressure. Check for a truly flat surface where you are standing the piece for glue up, then, as another poster suggests, adjust the clamp pressure/position to square things up. But watch out that your squaring up does not rack the piece on the horizontal plane, lifting one or more legs off the resting surface.
Mike Hennessy
Pittsburgh, PA
Everything fits, until you put glue on it.
Lay the sides on your bench and test them for twist/winding.
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