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Wood bought from the local home center does usually not have straight edges (usually kinked), and is often warped (bowing being most prevalent). I was surprised to see that at my local hardwood dealer, too (they sell pre-milled 1x and 2x boards).

The selection at the hardwood dealer was much better, with the warping much less pronounced, but it got me thinking. If the hardwood dealer can't get straight, flat boards with their presumably bigger and better machines, how flat and straight can I get them at home with a smaller jointer and planer? How long can I expect them to stay that way? Are some wood species more apt to warp than others (I was looking at poplar)?

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Short answer, yes you can get your wood more straight than you will find at the box stores, and even from your hardwood dealer.

It would stand to reason, as you say that they should be able to produce a straighter product, but the reality is they are dealing in volume, and so there are many factors. First, they are going to be using the cheapest quality material that they can reasonably get away with, as they have to turn a profit.

Second, this material is milled in volume, and usually is not given much attention to each individual piece. They will often just straight line rip the material on a saw to a rough dimension, and then send it through a moulder, with 4 cutter heads so it is 'straightening' all four faces in one pass. This gets it close, but ultimately not actually straight.

In addition they are kiln drying everything, and then it most likely sits outside unprotected from the weather for an extended period of time. The moisture content will change rapidly with the environment that it is left in, and while sitting in large stacks, the wood will expand and contract, and ultimately be left fairly warped.

If you take a piece of hardwood home, and straighten it properly on a jointer on two perpendicular edges, and then plane it to thickness, removing material as evenly as possible from the opposing faces (taking all of the material off of one face will cause even more warping/bowing), then you can get a very straight board. Furthermore keeping the wood in a more steady environment (out of the rain, limited humidity, closer to its final destination) it will maintain a more constant form.

Now beyond this, it must still be noted that wood will always move, and in any project built with wood, this movement must be understood and accounted for in the design. If you account for this properly, and accept it early on, you will be successful and happy with the final result.

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If the hardwood dealer can't get straight, flat boards with their presumably bigger and better machines

It's not about the machines, it's about the wood. Wood is inherently prone to warping because A) it's wood B) every piece is different C) it takes on and loses moisture from the surface so moisture content within the material is rarely completely uniform.

Don't underestimate B here, literally every piece of wood you handle for the rest of your life will be somewhat individual. Only quarter-sawn boards that have been well dried can be anything like uniform in the way they behave but even with that there can be some surprises.

how flat and straight can I get them at home with a smaller jointer and planer?

Very flat and very straight. For about five minutes.

Jokes aside you can get your wood perfect and return to it in just a few hours to find it was "warped off". Some woodworkers like to keep their freshly milled stuff in plastic bags, wrapped in a plastic sheet or immediately sticker it (stacked with spacer sticks) with weight on top to help prevent or minimise this.

Remember that the longer a piece of wood is the more pronounced the warp can be, but sort of on the flipside you should keep wood as long as possible for as long as possible as the old saying goes.

Are some wood species more apt to warp than others (I was looking at poplar)?

Yes. Modern commercially-grown softwood is very prone to warping because the trees are grown as quickly as possible and the wood is consequently weaker, and there's not much concern given to how uniform and good it is except in terms of how it matches the written grading standards, which are mainly about straightness of grain and frequency of knots and tell you nothing about how well it was dried in the kiln.

Hardwoods are/can be different because people want to do more important things with hardwood so more care can be taken with it, but some yards take more care than others and unfortunate exposure to weather conditions (not through poor storage, just a bit of bad luck, e.g. a spell of bad weather) can and will affect wood that was otherwise destined to be a little better than it ended up.

But remember that the individual nature of each piece can always assert itself, lovely straight-grained boards from a straight tree will always tend to be more stable than boards with any sort of irregular grain taken from bent or twisted trees (of any species).

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I understand (I think) what you are talking about. I am going to guess you have a small planer, like 12 in maybe? If you need a bigger thing look up router planer. Anyway They usually are warped and I put the blame on the grain pattern. the reason for the warping is because they do not cut it then glue it into strips. The best thing to do is buy the straightest boards you can get. Which I am sure the wider/bigger they get the more chance of warp. Take it home and joint on side flat (if not done already). Then go to the table saw and rip it into pieces of 2-3 in strips. Then glue them back together but watch the grain pattern. Do not do it the same like ||| or --- but alternate like |-|-|-|. that alone will help with warping in the future. Then plane as needed. The reasoning for that is both by using glue it tends to help keep the wood in line if-you-will. And you can take controls of how the grain pattern is. If you want some hardcore control of the grain pattern and alternating it then cut the wood into square strips. By doing this you can really have some flat boards. I hope I answered your question, comment if not.

  • Oh and simple answer is, no as long as you do it right :) – Ljk2000 Sep 27 '16 at 2:58
  • While your technique is good, and essentially the same as purchasing narrower boards then gluing them up with the growth rings in opposite directions to help prevent warping, turning boards 90° instead of 180° when gluing will work for painted wood, it will leave interesting patterning for a stained project. This could be used to your advantage, but is likely to be undesired by most folks looking for a stained finish. – FreeMan Sep 27 '16 at 15:05
  • I don't have any jointer or planer...yet :) – mmathis Sep 27 '16 at 15:06

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