Jointer straightening of long bowed, twisted pieces

[Tom M King]

Many have been mislead by more than a few telling how that the piece you can straighten on a jointer is limited by the length of the jointer tables. That is simply not true.

I needed two straight 88" long pieces of dry treated lumber 1-15/16 by 2-15/16. Normally, I keep a good supply of treated lumber drying under a shed for years. That supply is about depleted, since I've been tied close to home looking after my 106 year old Mother. The only piece I had left was a 16' 4x4 that I could get those two pieces out of.

It was bowed some, and twisted enough that you could look at it and see three sides. I cut it in half, and started with each piece with the convex side of the bow down, at first making a small flat spot in the middle. I just sighted it, and adjusted the next pass accordingly until the flat got longer and longer.

I wish I had taken more pictures, but hope these will give you an idea. Once I had once side flat, that side was held against the fence, and the second side flattened. I had to turn the piece end for end a couple of times in the process.

Sorry, I expect the pictures will be sideways, but hopefully they will be self-explanatory. These 8' long 4x4's were about as long as I would want to joint by myself, but have straightened edge of treated 2x12x16's plenty of time with a helper and a 3' bed 6" jointer. You just need to make a flat spot, and go from there. If the first couple of passes don't leave a flat in line with what you want, do a tapering cut of the flat part to get it in line. This is where you need to be able to see straight.

The first picture is probably after I had made 5 or so passes. The first 3 were taking 1/8", and changing to 1/16" after that. I was by myself, so didn't have anyone to take a video, but it didn't take that long. After straightening those two sides, I left them sitting for a few days to see if they moved any. These didn't but the longer ones I made out of 11 and 12' pieces I cut out of 4x6's, a few of them needed a little help with a no. 8 plane.

Do yourself a favor, and forget what you've heard about being limited to length because of the length of your jointer.

edited to add: I had a few more pictures, but we're limited to 8 per post, and I'm not sure the others would make things any more clear.

[Mel Fulks]

“Convex side down” . Is certainly correct and important. It often makes the board MOVE to straighter on the OTHER side at same time.

For years many were pushing the notion that concave side down was “safer”; that was wrong…but possibly once a good legal stance for
management.

[Thomas Wilson]

I am building a hand rail for my shop from air dried white oak. The stock has some cup and twist. Most of the parts will be 3-5 ft so no problem to get them square with a jointer and planer. But the two pieces for the T-shaped hand rail itself need to be continuous and start out as pieces 2” x 4” x 12 ft long. I will hand plane one face flat enough not to twist on the jointer judging by eye and winding sticks. Then I will mill it normally with jointer and planer.

You are using your jointer the same way I will use my No 5 1/2 hand plane to flatten a face. Your way takes a good eye and steady hand not to follow the twist as you feed the work piece through the jointer. Lacking your skill, I will have to take a slower manual method to establish the first flat face. My bench is only 76” so a 12’ work piece is a technical challenge. Not sure yet how I will support it while planing. Some sort of channel made of 2x6 I expect.

[Tom M King]

I cut 8 12' long pieces out of old, dry treated 4x6's. They were done the same way, but fortunately not as bad as that 4x4 started out. They were also handrail pieces. That was the batch that required a no.8 after sitting over a weekend. I only used the hand plane because there was not much left to feel safe dealing with it on the jointer.

There's no reason to follow a twist. The key area is on the outfeed table. Hold it down on the outfeed table without letting it waver, and it will stay straight from there. I have a hard time seeing how one would "follow a twist". edited to add: The fence is not in play on the first side.

You can see how these 12' 2x3's were supported. No bench. Just clamped on one of a couple of sawhorses. No reason to push down on a plane. The effort needs to go into the iron.