How do you flatten twisted 2x4's

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Forum topic by 4Doose posted 04-10-2011 10:51 PM 23259 views 0 times favorited 18 replies Add to Favorites Watch
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8 posts in 2597 days

04-10-2011 10:51 PM

Topic tags/keywords: removing twist remove twist twisted twist


After letting my fir sit in the garage for most of the winter to dry out and acclimate I fired up the jointer to begin milling.

I have a mix of 2×4 and 4×4’s that I am making my work bench out of. The 4×4’s dried well with no cup or twist. The 2×4’s, however, dont seem to have any cup but twisted up to 1/4 across the length.

Let me take a moment to disclose that this is the FIRST time I have used the jointer with wood I intend to use for a project. It is set up perfectly according to the owners manual. This is also my first project and am a complete novice to woodworking. Thought you may want to know who you are dealing with ;)

The 4×4’s came out perfectly flat and square on 2 sides. The 2×4’s are not proving so easy. Fortunately I stopped on the first board to seek enlightenment from some Jocks.

I had assumed that eventually I could mill out the twist with enough passes by stopping each pass when the lumber began to raise up off the cutter then start a new pass and go a little further each time.

It seems logical but alas it is not working. I am ending up with what looks like will be a fantastic long bow, all I need is a draw string now.

I stopped on the first board as soon as I noticed the board was not getting flat, just deformed.

I have looked through several books I have and googled my issue but I am not finding a solution to my problem.

The 2×4’s will be glued together to form a 3” thick bench top so any twist is unacceptable.

So can anyone educate me on the correct procedure for flattening these twisted 2×4’s?

Thank you,

-- David, maker of fine sawdust --

18 replies so far

View patron's profile (online now)


13600 posts in 3311 days

#1 posted 04-10-2011 11:14 PM

if they are twisted 1/4”
you will loose 1/2” overall
by the time you get them straight

i do those by keeping the crown up
and only pushing down on the ends
(and not twisting the board as it goes over the cutters)
if you push down on the middle
it will spring back when you have done the pass
it just makes it thinner but still curved
1 face and 1 edge on the jointer
the other 2 sides on the planer
or the table saw
you will loose wood this way
but it is the only way to get it flat and straight

-- david - only thru kindness can this world be whole . If we don't succeed we run the risk of failure. Dan Quayle

View Kevin's profile


462 posts in 3175 days

#2 posted 04-10-2011 11:25 PM

Pretty much what David said there. Make short passes on each end multiple times until the cup is almost gone then start face jointing. After it’s flat then take it to the planer.
Here is a good video showing what you are wanting to see I believe. About 4 minutes into it.

-- Williamsburg, KY

View Loren's profile (online now)


10283 posts in 3617 days

#3 posted 04-10-2011 11:53 PM

Pine and fir are mostly pretty easy to bend a bit, so while I do recommend
tuning out some of the twist, you don’t have to get it all out. Use heavy
clamping when you glue if necessary. What counts is the finished slab,
not the perfection of the boards that go into it.

Your finished slab may misbehave for awhile due to the stresses in the
boards inside it, but that’s something you’d be dealing with even if
every board was perfectly flat and square.

Jointing on a jointer takes a lot of practice and self-critiquing. The
machine does what it does, but it’s your understanding of how it
planes that determines your results. I recommend practicing with
a hand plane to flatten some boards and then you’ll understand how
flattening works better.

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8 posts in 2597 days

#4 posted 04-11-2011 12:21 AM

Thanks for the information.

While waiting for some replies I went back to the jointer and the piece of wood I already started on.

I dont know why the 4×4s turned out so nice but they did. Dead flat end to end and perfectly square on 2 sides.

The 2×4 though.. wow. I cant yet tell what I am doing but what ever it is its making the board far worse than ot was when I started. I flipped the board over to the untouched side and scribbled all over it with pencil to see exactly what was getting removed as I passed the wood across the jointer.

Interestingly I did see that the opposite high ends were getting planed down, as I wanted. However, as the high spots begin to flatten out the leading edge of the board starts to become thin and about midway down the board it stops touching the cutter and I start making a new long bow again. Its a strange looking piece of wood not with the ends about 1” each and the center about 1.25”

So as Loren mentions above I can see that a lot of scrap wood will become long bows before I know what I am doing. Until then the workbench wood will be set aside and a lot of scrap pallet wood will be coming home from the work dumpster to practice on.

-- David, maker of fine sawdust --

View BurningLizard's profile


71 posts in 2660 days

#5 posted 04-11-2011 01:34 AM

Get a metal detector for that pallet wood. I chipped my jointer knives on a hidden nail in some pallet wood.

View 4Doose's profile


8 posts in 2597 days

#6 posted 04-11-2011 01:55 AM

“Get a metal detector for that pallet wood. I chipped my jointer knives on a hidden nail in some pallet wood.”

Just so happens I have one. I will indeed, thanks for the tip.

-- David, maker of fine sawdust --

View Grandpa's profile


3259 posts in 2645 days

#7 posted 04-11-2011 02:05 AM

Put the concave side down and go the full length of the board until the jointer cuts the full length then it should be flat and straight. Then take it to a planer or a saw and make the opposite side parallel. Don’t apply pressure to the board or you will defeat the purpose of the exercise.

View bubinga's profile


861 posts in 2637 days

#8 posted 04-11-2011 02:38 AM

The first thing you can do to ,greatly ,reduce the amount of ,crook or bow ,is to cross cut ,the stock, if you have an 8 foot length ,and you only need a ,2, 3, 4, 5 or 6 foot length,cross cut the stock, closer to ,the length you need,but leave extra.
If your jointer out feed table is to high, you will get a convex surface, if jointer out feed table is to low you will get concave surface,but this may not be the problem.
Feeding stock through jointer, When one third of stock is ,on out feed table ,put pressure on out feed table ,only, for the rest of board.

Here is a Video

-- E J ------- Always Keep a Firm Grip on Your Tool

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861 posts in 2637 days

#9 posted 04-11-2011 03:07 AM

Here’s another Video—
I agree , you want to keep pressure light , this is shown ,in the first video link
But you can put more pressure on inch and a half , stock than you would on ,3/4 stock

-- E J ------- Always Keep a Firm Grip on Your Tool

View AaronK's profile


1506 posts in 3434 days

#10 posted 04-11-2011 03:21 AM

to second Grandpa, i believe you problem is coming from the application of pressure on the board as it moves across the jointer. the 4×4 is much harder to deflect than a 2×4, which is why you dont see the problem there. you want to keep pressure as light as possible – just the weight of the board itself if you can do that.

View DLCW's profile


530 posts in 2624 days

#11 posted 04-11-2011 03:31 AM

As soon as you get them home, wrap them in the stretchy plastic wrap (used in packaging). Leave just the end grain exposed. When you are ready to use them unwrap them and use them right away. I’ve used this procedure for years and I always have straight 2×4’s when I need them.

-- Don, Diamond Lake Custom Woodworks - - "If you make something idiot proof, all they do is make a better idiot"

View 4Doose's profile


8 posts in 2597 days

#12 posted 04-11-2011 03:11 PM

I have to remember I am not machining steel anymore. I believe I am putting excessive pressure on the board as many of you mention. I will watch the videos later and when I get home from work tonight I will try out a feather touch and see what happens.

Thank you all for the insight.

-- David, maker of fine sawdust --

View Nomad62's profile


726 posts in 2928 days

#13 posted 04-11-2011 06:02 PM

2×4’s are usually cut from less quality parts of the log, sometimes even from poor quality or very small logs, as they are the smallest cuts most mills make for lumber; bigger wood is more likely from a more stable part of the log. The best wood is reserved for bigger pieces as they sell for more money. 4×4’s are much more stable due to their mass. There is a lot to be said for studying the growth lines in a board in reference to how it will move when drying, you may want to snoop around a book or three as the info is good to have if you plan on using green lumber to work with. I have found kiln dried 2×4’s at my local HD store at the same price as non kiln dried, they may be a better option for this type of project. I guess none of this is any help today, but hopefully may help you in the future. Lastly, you may want to consider slicing a 4×4 down to your 3” for that top rather than relying on a glue up.

-- Power tools put us ahead of the monkeys

View GregD's profile


788 posts in 3106 days

#14 posted 04-11-2011 10:08 PM

Maybe change your plans and go for a butcher-block style top rather than one where each strip runs the entire length of the bench. As bubinga suggested, cut the 2×4s into 3’ or 2’ lengths and they will be easier to joint and you will get better yield. The downside is that it will take several to make up the desired length of your benchtop. With a 3” thick top – cripes that is thick – I don’t think that will be a problem so long as you stagger the joints.

-- Greg D.

View AaronK's profile


1506 posts in 3434 days

#15 posted 04-11-2011 10:17 PM

very good idea Greg, something we can all keep in mind.

showing 1 through 15 of 18 replies

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