How do you flatten twisted 2x4's

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

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.

http://www.youtube.com/watch?v=UqVkISnNx0w

-- Williamsburg, KY

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.

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 --

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

“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 --

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.

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 http://www.youtube.com/watch?v=qqqa6W8m6Y8

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

Here’s another Video—http://www.youtube.com/watch?v=UqVkISnNx0w
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

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.

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 - http://www.dlwoodworks.com - "If you make something idiot proof, all they do is make a better idiot"

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

-- David, maker of fine sawdust --

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

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. -- the price of freedom is tolerance

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