I have been designing a Greene & Greene influenced ceiling light fixture for my kitchen to replace the cheap ‘80s aluminum frame. For this project, I am trying to avoid making it bulky by using thinner stock (1/4”) in most places. However, I find myself getting rather frustrated because after jointing an edge then milling to the final dimensions, nearly every board stills up warping or bowing to some extent.
I am therefore curious how much tolerance I should allow for in each piece since the stock is thinner and can usually be straightened with minor pressure. In most cases, I am now considering joining two pieces together at right angles to help correct these deviations. Does anyone else suffer from these complications? How long should I let the wood “relax” after initial ripping to let the stresses subside before jointing and cutting to final dims?
The wood is kiln dried walnut that has acclimated for years now.
Replies
z,
Sounds like the stock you selected had stress within it and was released when you milled it, in spite of how long it had acclimated. Acclimation of stock, at least in my experience has had little or no effect with regard to stress in wood. You do sticker pieces after milling them when they are going to sit at least overnight?
I keep all my stock stickered from the time it comes into the shop until it is assembled into a piece. Consequently I have piles of stickered stock in various stages all over the woodshop. My shop is small so I kinda have to limit how many projects going at one time and sizes of the pieces does matter too. :-)
Stickering will help keep flat stock flat, assuming there are no stresses in the wood itself because it allows air to freely circulate around it so all sides can breathe. Of course if you started with a warped/twisted board then it may end up as you described, even with stickering.
Stock selection is one of the most important steps to ensure a successful project; keeping it stickered will go a long way in helping you keep things straight. I let my milled stock rest for at least 3 days, sometimes more. There's no set amount of time as far as I know but I suspect atmospheric conditions may also play a part in this madness I call a hobby.
Regards,
Agree with the need to keep all surfaces exposed. Another approach I use is to keep all stock standing on end as long as possible - especially after planing to thickness. Another approach I use for thin re-saw panels is to return it to its original storage place (garage in my case) until final sanding and then immediately place in frames.
Jerry
Ply Wud
Zom...Beer...Rose... OK i Give.... but my what nice teeth you have...
I am pretty sure this is why they invented plywood. The opposing direction of materials and the stresses involved keep the whole flat. Homemade plywood can be pretty kewl as well. Otherwise, I would be searching for plain sawn material where the grain is running parallel for the width of your board, say 4 ot 5" for a fan blade. Highly figured wood has lots of stresses and will move more but looks great. IE the veneer approach.
If you are looking 1/4 material and you start with 3/4" you have to remove some of the material and let it set for a week in your shop. Then replane and flatten. Normally 1/4" material becomes a panel in a door and the frame stabilizes the material or perhaps the sides of a box where the joints themselves keep it more stable. Regardless it will want to cup on you if you are taking it from thicker stock.
AZMO
I was walking by an isle at Rockler today and they have lots of exotic stock in 1/4" thickness. Some was nice and flat and some of it was rocking chair material.
You've gotten some excellent feedback, hope no one minds a bit of background info on the possible causes.
Not sure from your original post if your 1/4" stock becomes unflat as soon as ripped free, or initially is flat but with time bends/twists, ... If the former you likely are encountering the internal stresses mentioned earlier. There are several causes of internal stress, and some species of wood are more prone to them than others. "Understanding Wood" by Bruce Hoadley suggests walnut is pretty stable, but there's always a rogue board or log. Quartersawn stock is usually the most stable, so look for some in your inventory, or if necessary make some by resawing some flatsawn stock, and see if that stays straighter for you.
Generally the amount of moisture is higher at the exposed surfaces of wood and lower internally. Changing moisture content will cause wood to move. Thus the general practice to remove the same amount of wood from both sides when planing stock - we want similar moisture content on both sides, and the board probably had equal moisture content on the original surfaces.. In this instance you might plane a board to 1/4" width and let rest for a week or two (with air reaching both sides) and then ripping some 1/4" strips to see if they behave.
If your strips only start to bend after a day or so, and you're leaving them lying flat on a surface, it's likely uneven moisture mentioned in an earlier post is the problem. That's the reason for suggesting you sticker the strips. You could even hang them with a piece of string or tape, as long as the entire strip is exposed to the air so all four sides will absorb or give up moisture equally.
The thought of trying to run thin square strips though a power jointer gives me chills, so it might be difficult to follow conventional practice for straightening and flattening boards when you're starting with 1/2" squares. I've been working a lot recently with quartersawn and riftsawn cherry and have found it extremely stable. Occasionally I rip a 3/16" thick (or so) strip from one edge to bring a piece close to final width, and those strips, some up to 42" long, generally have stayed very straight. Hence the suggestion to try quartersawn stock.
This forum post is now archived. Commenting has been disabled