I don’t have a lot of woodworking under my belt, so please bear with me. I bought a few feet of 1x8 mahogany to make a desktop and some shelves. The board looked straight when I picked it out, but once it was cut down to size, I noticed some warping. I intend on joining two of them on the edge to make a desktop, so getting them straight is pretty crucial. The boards are already on the thin side at 3/4", so I would like to avoid planing.
Any tips on how to straighten mahogany planks without removing material?
I’m no expert, but I’ve experienced the same thing a few times. I’ve started rough milling, then leaving the boards overnight to settle before finishing milling the next day.
Can you describe how they’ve warped, and how much? Often it’s ok if they move a little—the process of joining them into a panel will correct slight movement, especially if you reinforce them with biscuits or dominos.
How bad is it? For longer boards, this is inevitable to some degree and doesn’t mean it’s a deal-breaker.
There’s more to this answer in the preventative sense which I’ll add to the bottom of this. For now here’s what I would try:
If it’s really bad:
The bow / warp / crook / cup means the board is drier in some places than others. Milling will expose wet fibers that dry at a different rate than a non-milled side. You could wipe a damp cloth or rag on the inside of the bow and let it sit for a few hours. If it’s really bad you could wait overnight.
When storing it, avoid leaving it flat on a table. Put some stickers (sticks of wood) underneath, evenly spaced so air can circulate all around.
During the Glue-Up
Use Cauls. A long stiff straight piece of wood that you can clamp down over the seams, that will help keep the glue joint straight.
Another option is to consider using the biscuit joiner to make space for biscuits. For this I might recommend clamping your board to a workbench so it is flat, then using the biscuit jointer to make your biscuit mortises. This should help with alignment during glue-up.
Preventative Rough milling, closer to final milling, glue-ups, more material removal (sanding or planing)
Rough milling (as John mentioned, he’s spot on). Rough mill, let the wood acclimate then mill again. Dending on how much you’re material you’re removing, cutting away, planing, or jointing you may want to do multiple mill steps.
Plan on removing material again after glue-ups as well. If you want your final dimension to be 3/4", give yourself some wiggle room of an extra 1/16" or more if you plan on a wild glue-up.
Time
The more time it has to acclimate in the space you’re working in the better your working experience will be. Keep projects in mind for where they’re going too. If you make something in the winter, expect that there will be some expansion by the time summer comes around.
Thanks, I’ll let them sit on an even surface overnight before doing anything drastic. They’re 42" boards, and if I lay them with the cupped side down, there’s about 1/8" between the floor and the middle of the board. There’s some twisting as well, but it’s the cupping that has me more concerned.
I’ll definitely be giving the damp rag a try. The glue-up tips answered a couple of questions on my “cross that bridge when I get there” list. I appreciate all the info!
Lovely Mahogany! More than likely, what you have is Sapele (area of Africa, it comes from), and nowadays, if you don’t know how to pick the boards, a lot of boards have stress. I have seen it start moving away from a blade as i was cutting it or bog down the motor of a table saw if it was caught between the blade and the fence. Climetising helps the boards some times. The problem you have is that S4S boards or what i generally called dimentional lumber or one by’s is 3/4" so as you stated not much room for error when gluing. I would go the caul way mentioned above, at the ends and maybe at the center. I would skip the biscuits’ o dominoes. The logic is that you would create a void that is going to be filled with glue that has a lot of moisture and moisture is not your friend at this time. But is up to you. Anyway, once the glue dries, at least overnight, see what you have. If it still warps, you maybe ok as long as you can get it flat. You can use braces to secure it to the side of the desk or at the ends and center to keep it flat. Use glue and screws every six inches. Pre-drill the holes and start about an inch or so from the edges as Mahogany that has stress is also prone to split with mechanical fasteners. This recommendation is if your boards are warped only. If they are cupped (inverted “C” lokking at the end grain) you mentioned in your follow up, there may be not be much saving on those boards unless you can split them right in the center.
In the future if you’re going to glue boards, try getting 13/16" or 7/8" known as rough lumber around here. You will save money and get experience in milling the lumber, gluing, and have room for errors on the way for your boards to be flat or get to the standard of 3/4."
That’s extremely helpful! Thanks for taking the time to share. After checking them out again, it doesn’t seem like they’re cupped on the end grain, just warped. I’ll go the caul route for the glue up for sure. Is there a specific material you’d recommend using to make the cauls?
Just use a piece of scrap wood with a straight edge that is at least an inch thick flipped on the edge, inch and a half or wider would be better. I have used store bought and home made cauls and found them to be too much a hassle. Personally i just use “F” clamps to do that kind of alignment when i run into that kind of a problem during glue-ups. For you probably the straight boards would be much easier to do as you also fighting the glue setting up on you. If you decide to go this simple way. Once glued if you don’t like the outcome you can always rip the board on the glue lines and try a different way. You will loose about 1/4" of material in each cut you make though (1/8" thickness of the blade and then some to joint the board to get a clean edge).
I forgot to mention that if you have wide boards, 6" or wider, it may help if you rip them in half. Or at least the warped boards. Quick tip: If you do this, alternate a narrow board with a wide board to make it look intentional.
Just additional information: other kinds of lumber that tend to have “stress”
Red Oak that has arched veins or grain and a wavy end grain, it will have stress. Usually wiil come from the Apalachian zone of the country.
Birch if you can find it, it will twist, cup, bow and go every which way if you dont climetise it slowly.
Spanish Cedar, if it has very visible veins or grain, more than likely it will have stress.
Red Alder, this one is easy to spot, the board will be already warped or twisted in the lumber yard.
Strangely enough “real Mahogany” (google it) is very stable and does not do any of the above.
Several people have recommended cauls, which they described as thick straight pieces of wood. By “straight”, they really mean it has a flat surface to clamp against your board. But that actually depends on the geometry of the setup. You may find that clamping the cauls together near the edges of the piece causes them to bend so that they aren’t making good contact with your piece in the center. In that case, you may need to sand a slight curve into the cauls, making them thinner at the edges, so it bows away from your piece. Clamping it then pulls it flat, making contact uniform across your piece.
Also, putting packing tape on the contact surface of the caul will keep wood glue from sticking to it.
@mgmoore I have been using this technique for my glue-ups since you showed it in the table router class and now keep a few extra boards handy just for this.