Replies

1. 
   VomSorb | Oct 25, 2004 09:42pm | #1

   All glue-ups MUST be left over finished thickness to allow for flattening and final thicknessing immediately before being put into use in the project.

   If you plane the individual boards to finish thickness, then glue them up, there is not a whole lot you can do to salvage the situation. 

   If the amount of bow is slight, you may very well be able to put the into the project anyway.  We need to know what part(s) for what particular project you are making.

   
   

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   Edited 10/25/2004 2:42 pm ET by cstan

1. 
   pipes | Oct 25, 2004 09:53pm | #2

   the boards i make are usually for the sides of units such as chest of drawers, bedside cabinets etc. i do leave them oversize and then plane them to finish dimensions. if the work has dadoes for shelves or drawer runners the problem is reduced when glued up but the bowed boards make any machining prior to gluing up difficult.

1. 
   VomSorb | Oct 25, 2004 10:09pm | #4

   For those parts the panels need to be as close to perfectly flat as possible.

   Your next step is to expand your skillset to include flattening glued panels. 

   An obvious and expedient solution would be to flatten one side with hand planes then plane the other side to finish thickness.  You should end up with a flat panel with parallel faces.  However, with the species you're using this cannot be done significantly ahead of time as pine is notorious for movement. 

   In gluing up a panel, all you really need to do is shoot the edges (machine or hand tools) so that you can do your glueup.  After the panel is glued, you then proceed to flatten and plane to final thickness. 

   Edited 10/25/2004 3:11 pm ET by cstan

2. 
   jackplane | Oct 25, 2004 10:06pm | #3

   When clamping, clamps should be alternated over and under the stock. The thicker the stock, the easier it is to clamp flat. Check with a straightedge and adjust as needed.

3. 
   JohnWW | Oct 25, 2004 11:17pm | #5

   Flat sawn wood as it gains and loses moisture with changes in the weather, or if it is brought into a heated or dehumidified shop from a damper storage area will cup, it is inevitable.  Some pieces will cup more than others so the panel may not stay flat even if you alternate grain direction of the strips.  The wood may also cup over several hours after it is planed down initially, due to moisture loss and stress redistribution.

   The first part of the solution is to use quarter sawn wood in critical applications.  Next, when you to bring the wood into the shop, sticker it, and let it adjust to its new environment for a couple of weeks before using it.  When you start the job, plane and saw the wood to close to its final dimensions and allow it to readjust, again in stickers, for a few days before final dimensioning and then glue up the panel immediately. 

   Once the panel is glued up, install it in the finished piece as soon as possible so that any further wood movement will be controlled by the joinery.  If the panel can't be used right away, wrap it in plastic, even if only for overnight, to keep it as stable as possible until you can get it installed.

   John W.

1. 
   pipes | Oct 25, 2004 11:45pm | #6

   i must admit that i like the idea of the plastic wrap. here in england in a lot of diy shops the timber they sell is wrapped in plastic and it does keep it straight etc. you do have to use it quickly though to minimise warping when you take it out of the wrap.

1. 
   JohnWW | Oct 26, 2004 12:48am | #7

   If you are buying the wood wrapped in plastic, I would recommend that you unwrap it and allow it time to adjust to your local climate and shop conditions as I described in my first posting.  It just isn't possible to do good work with boards that are moving as you work with them.  Having to  "use it quickly", isn't a good approach for furniture making.

   To avoid the temptation to use wood that hasn't settled down, I try to keep enough stock on hand to be a few months ahead of my immediate needs.

   By allowing the wood to stabilize fully, planing accurately with well tuned tools (hand and power), and carefully gluing up the panel, I never have to flatten a panel once it is glued up.  I just use a scraper to correct any minor misalignments between the boards and the panel is ready to use.  Handled this way, even large table tops need only a few minutes of cleaning up to have them in a finished state.

   White pine is more prone to cupping than many other woods but it is still my favorite for cabinetmaking, it just needs to be handled properly.

   John W.

   Edited 10/25/2004 6:03 pm ET by JohnW

4. 
   hammer1 | Oct 26, 2004 07:40am | #8

   I always use culls to clamp the overall surface flat at the same time I edge clamp. There's a thread about "Larry's clamp" right now to the left. A pneumatic version of the wooden culls and F-clamps I use. I do a lot of raised panel glue up. I prefer to surface first which makes flattening culls work much better. I use strips of wax paper between the culls and the work to prevent gluing down the culls. Most of my culls are 1x3 oak, joined straight, not crowned. I place one on edge on the top and one opposite on the bottom and use F-clamps to pull them together. One set in the center is OK for short glue ups, I use a pair at each end and more in the middle when doing table tops or long pieces. There's no worry about your pieces bowing or bursting out of the clamps. Set that joiner up square, you shouldn't have to compensate. Just worry about the grain direction and keep it tight to the fence.

   Beat it to fit / Paint it to match

1. 
   JohnWW | Oct 26, 2004 09:43pm | #9

   Hammer,

   A minor point, but I think the proper name for the wood braces you use is "cauls".

   While they do work, cauls add considerable extra work to a glue up and aren't needed if the stock is properly prepared so that only light clamping pressure is needed to close the joints.  In my experience, both in teaching and just observing other woodworkers, most people use too much glue and too much clamp pressure when gluing up panels which forces them to take extra measures to keep the panels flat.

   John W.