Hey folks,
I am glueing up a desk top that has a 45 degree seam where two sides meet. The desk has two wings, each one is 6 feet long x 24″ wide. I know there will be wood movement in the width, but will there be movement along the 45 degree seam? can I fasten the two sides together at the seam with a cleat fastened underneath?
And, if I have to use oblong holes to allow for movement of screws, which way do I make the groove?
Stumped!
Buck
Replies
Yes. Not only will there be movement, but the miter angle will change. For example, if the desktop is flatsawn red oak, the overall width will vary about 1/4" for a 3-point change in moisture content (not at all unreasonable). If the boards are at 6% MC when you cut the angle at 45°, then at 9% MC the angle will be 45.3°. This means that if you hold one wing of the desk fixed, the other wing will swing in an arc, with a total movement of the far end of about 3/4".
To answer your question directly: wood movement along a 45° cut line is about 70% of the movement directly across the width.
-Steve
nice answer.
did ya get all that buck?
did ya get all that buck?
I found that so funny I am cleaning my Jim Beam off my screen!
will g,
over the years, i am often amazed at the sheer volume of data some of my fellow knotters can keep balanced between their ears! i usually have to reread posts, such as steve's, several times to get the jist in 'em. i was taught math at gunpoint by some very scary nuns, as a child, and this has left me weaker than most, when it comes time to applying arithmetic to wood. i once burst into tears when i found the exact center of 14" diameter pedastal, but they were tears of joy.
ps
what a waste of good jim beam!
ps.. I think the same. Went to Catholic schools all my life.. I THINK I learnt something!
OK so NOT what I thought they waned! My nuns were NOT evil things.. Just like a mother.. Just wanteded us to LEARN something! And I took up woodworking.. I wonder?
I was taught math at gunpoint by some very scary nuns..e!
All the nuns I remember were beautiful women. OK so for Sister whats her name!
REALLY! I love math but not very good at it.. I tried really hard to do it.. I CAN come
up with the answer.. BUT I have no idea why I could or what the answers meant!!
Really.
Sort of like a first kiss from your furture wife and then she says 'I did not brush my teeth'.. I old her, ME EITHER!
will,ya make math into romance! i should have been as fortunate. no, will, my very good man, it was uphill all the way and a whack with the ruler for your troubles. from time to time i pick up a geometry book and give it my best, only to be bested by the eternal and infernal math block that's dogged the best days of my ww life. then there's the from time to time when the need, as in my next paycheck's hangin' on this one, that i slog,(ah, D. rumsfeld), right to the bottom of the mysterious math and actually get something worked out. at these times, tears, well up in gratitude.eef, math-blocked yet holdin' his own.
And I use this..
OK to download.. I think a wonderful program I picked up on the net..
Your statement.. ya make math into romance!
My statement.. 1 plus 1 makes TWO!
I looked for the picture but did not find it.. Long ago a made a 'Spanish' style table. Sort of Mexican it turned out to be. I used carved (by a friend that could carve.. A Native American) ... Each corner was a hand carved block of wood.. Had it for years and nothing broke.. My oldest daughter has the dining table.. She loved it so I gave it to her..
Edited 5/29/2009 1:29 pm by WillGeorge
I just did this for the Family.. Gave it to him last week.. A wonderful family and the greatest children to grow older with..
And the words...
Aho! Hizakisana hinikaragiwi.
I greet each and every one of you. As in: Relatives and friends:
And I forgot to say... Each in here are good and bad.. And I love ya all anyway!
Edited 5/29/2009 2:07 pm by WillGeorge
Wow, now that's an answer. So, another engineer turned woodworker eh.So, given that, would you try to secure the wings with a cleat and allow for little wiggle room?Buck
If it were me, I wouldn't use a miter joint.
If you hold a gun to my head and force me to use a miter joint, I'd make sure that I cut the joint when the wood was at its driest, join the two halves tight at the front, and then let the back ends float free, with just a loose cleat underneath to ensure that the movement is restricted to the plane of the desktop. The miter will open and close with the seasons, but by keeping all of the movement at the back, it will be less noticeable.
-Steve
Thanks Steve,I wouldn't hold a gun to your head, but, I might hold one to my head.I will go with your suggestion to put the cleat at the front. I guess I should have queried this before I was putting it together.You've been a great helpThanksBuck
Well, what I did is pretty much what John has recommended.I made the joint tight, screwed two cleats across the seam to keep it flat and secured two pieces of maple on either side of the joint, parallel with the joint. I then ran a clamp across the seam and secured the joint (no glue). My next step is to replace the clamp with a couple of bolts.I should mention that I have surrounded the top with a 2" border using Kane tsugi joints,..Gasp ...(see FWW # 200, master class). And, yes, I have allowed the joints at the back of the desk room to move.All in all, the desk looks great, I just hope it doesn't explode when the humidity goes up. Did I mention that the desk will reside on an island?thanks for your help.Buck
I would make the joint tight, this is a perfect application for cross bolts set into pockets on the underside of the joint along with a series of loose dowel pins to keep the surfaces of the two halves flush with each other. I wouldn't try to glue that long of a joint.If you allow the joint to open and close whenever the weather changes it will look very sloppy. You will have to allow one of the wings to slide over the base it is on to accommodate the movement, but that is easy enough to do using one of the standard techniques that allow table tops to move with moisture changes.John White
Shop Manager for Fine Woodworking 1998-2007
Those other guys must be mind readers, or maybe it's my lack of reading comprehension. But I cannot get a good mental picture of what exactly you are attempting to do. Sides, wings, cleat..... where they all are in relation to one another on your piece.... I can only guess. I'd like to see a photo or a drawing. Those others may just be guessing too.
Looking into my Bubinga ball (woodworkers aren't supposed to use crystal ones), I see the equivalent of the corner of a flat, mitered picture frame on steroids, each side being 24" wide by 6 feet long. If made of glued-up solid wood, as opposed to cabinet-grade plywood, I also see disappointment in someone's future, as pets and small children fall into the expansion-created gap. ;-)
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