Replies

1. 
   mudman | Sep 25, 2004 05:56am | #1

   Correy,

   A lot depends on the material and quality. I build a lot of built-in and office furniture. When I need to join up two table as you describe I miter it and use specialty hardware that pulls the two pieces together. I have used it on laminates and solid wood with no problems. For the miter I use the same technique that counter top installers use. I use a router and cut both miters at the same time. This leaves a gap free miter even if the cuts aren't straight. If youve never seen this Ill try to explain.

   here is a link http://www.rockler.com/ecom7/product_details.cfm?&offerings_id=349

   I would be wary of using the tongue and groove technique you mention on solid wood because the miter will open sooner or later do to expansion and contraction. Think of the miters on the door casing in your house. The reason they open is because the trim expands across the grain. A table top would be much worse. Good joinery will not prevent the movement, you must anticipate it. With the fasteners you can tighten the joint as necessarry. I imagine others will know more "traditional" methods. But can't think of ever seeing one.

   Mike

   please excuse my spelling.
1. 
   Jamie_Buxton | Sep 25, 2004 07:40am | #3

   Mike --

     You say "I would be wary of using the tongue and groove technique you mention on solid wood because the miter will open sooner or later do to expansion and contraction. Think of the miters on the door casing in your house. The reason they open is because the trim expands across the grain."  

     I don't see it like that.  The miters on the door casing open because the casing can't move.  It is held at 90 degrees (or whatever) by the wall it is nailed into.   The table, in contrast, can move.   If the joinery along the miter is tight, the angle between the arms would change as the wood expands and contracts due to humidity changes.

   Jamie

1. 
   hitai | Sep 26, 2004 11:54am | #4

   Roger that!

   The  miter joint will be Ok as long as the ends can move. Good idea to use stable wood .  I have had tops like this in service 20+ years  with splines or biscuits.

   I have also used a Herring bone layup that was stable and looks pretty cool too.

2. 
   mudman | Sep 27, 2004 07:33am | #6

   I know that it seems that way but it is actually is more complicated than that. What I am about to say is from a mag article, either FWW or JLC I forget, and it is hard to describe. If you cut a 45 and then the wood expands across the cut, the angle is no longer 45. It becomes less, or closer to 90 if you think of it that way. Draw the picture and you can see it. Imagine a board with a 45 cut on the end expanding from 6 inches to 6 feet, by then the angle will be less than 15 degrees. Obviously that is a ridiculous example but it helps illustrate. Trimmers have been trying for centuries to come up with a slution to the mitered casing problem. I am not saying that the joint is doomed to failure, I've never tried it. You are compareing it to a bread board, but bread boards are not glued. sometimes you might glue the middle 3 inches but it must be allowed to float, that is why dovetails are used. Unless it is an $8000+ super high end "hand made" type of piece you would be hard pressed to do better than those fasteners with a unglued tongue+groove joint to maintain alignment.

   Mike

   please excuse my spelling.

3. 
   mudman | Sep 27, 2004 07:38am | #7

   Ha Ha,

   I re-read your response and I agree.... as the angles of the miters change the overall angle will also be able to move. Assumeing the end of the table dosen't weigh too much and acts like a fixed piece.

   Damn, I thought I was sounding all smart and stuff...... I better go back to the shop. OK it's a garage, what ever.

   Mikeplease excuse my spelling.

2. 
   correy | Sep 28, 2004 07:05am | #10

   hey mike,thanks for the thoughts.the top I'M to build is to be installed on top of some base cabinets.(24" depth).Then on top of the base sits a 14" deep book shelf.the shelf on top would resemble a upper cabinet with out a bottom(showing the top)that will cross the long miter joint at  45*,maintaining the 10" set back of the top case from the edge of the top.the wood I'm going to use is Penn cherry,5/4,from groff and groff lumber in Penn..So what I mean is that the "table top" will be partially concealed,all but 10 or 11".I'll probably even cut most off that point right off in the back,what ever that extends out beyond the back of the cabinet.I kinda wanted to join and spray finish this L-shaped top right at my shop, then take it to the site and just set it down in one piece.Done. Well, a few slotted screw holes to hold it down.I was concerned with what the expansion and contraction would do to the sprayed on (hvlp)"hand rubbed" finish. any other thoughts on that any one?thanks for all the replies. Was really surprised.

2. 
   professor | Sep 25, 2004 06:07am | #2

   Mike,

   You are on the right track with the breadboard style joint.  Just make sure that you keep the tenon notched back from the end slightly (maybe an inch or so) to allow for concealing the inevitable wood movement in a cross grain situation.  Also you will have to pin the joint in the same manner as a breadboard with the holes in the tenons (holes for the pins) elongated as you work out from the center or whichever edge you decide you want to keep stable. 

   Elongating the holes in the tenons ( not the other top) will allow the tenoned piece to move across the grain without breaking the joint.  Use glue only on the part of the tenon which you don't want to move  as the pins will take care of holding the two pieces together. Ohe other thing: you will have to make the mortises a little longer than the width of the tenons so that the movement is not restricted across the grain.  Again in the same manner as a breadboard end.

   Hope this helps

   Mark

3. 
   robkelly | Sep 26, 2004 10:07pm | #5

   I am typing this on an L-shaped table/desk I built 20+ years ago which is 96" x96" and 26" wide. The L is joined with a 45* cut and held together with 3 tite-joint fasteners. It's worked fine all those years, and survived daily use as well as 2 disassemblies and reassemblies for moving. The wood is 7/8" hard maple with 3" walnut banding.

4. 
   eddiefromAustralia | Sep 27, 2004 08:31am | #8

   Correy,

   Google on mason's mitre (or miter, depending on the part of the world the document's written in)

   This is the joint of choice for particleboard countertops or others with a moulded front lipping.

   There's nothing wrong with a full mitre (except that the pointy end of the mitre can be brittle) - just wastes another foot or two of material in manufacture.

   The two sides of the countertop are held together with benchtop (edit: also called countertop or worktop) connectors, oddly enough.  No glue req'd.

   Cheers,

   eddie

   edit:  a few links that describe what I'm talking about

   http://www.diydoctor.org.uk/projects/mitering.htm
   http://www.kitchenfix.com/Worktops.htm
   http://www.lincolnsentry.com.au/Product.aspx?id=571
   http://www.yor-appliances.co.uk/store/0,proddetail,70726f643d594b564235253246313530,00.html

   
   

   ---

   Edited 9/27/2004 1:44 am ET by eddie (aust)

5. 
   Patto | Sep 28, 2004 01:07am | #9

   Have you though about getting the thing into and out of the room? I very nearly got caught with this in my fathers kitchen a cople of years ago with a bench top, and a knock down joint, rather than an impressive permanent one, would have been handy

   Dave