Making Raised Panels Flat

Advice on how to joint, plane, and glue up the pieces to achieve a flat door panel. August 31, 2009

Is there a way to make raised panels perfectly flat without having to buy the really expensive machinery? I currently joint 3" to 4" boards on my 6" jointer. When I glue them up, I keep the jointed sides face up and align them to keep flat (not all align perfectly). After dried, I plane them on my 16" planer flat jointed side down. Problem is that they don't all end up as flat as I would like them to be. Can anyone help?

Forum Responses
(Cabinetmaking Forum)
From contributor F:
I glue up panels all the time that only need a bit of finish sanding when they come from the clamps.

Rules... You must face flatten your stock on the jointer and then plane with the jointed side to the planer bed.

After flat and planed to .010 to .020 over desired thickness, you work the edges on the jointer. You must set your jointer fence so that it will joint the edge square to the face. Set two boards together on edge and test with a straight edge... adjust the fence until they will stack on edge and be flat.

Now, brush out a good even coat of glue on one edge of a board that is standing on edge on the bench. Place the mating board's edge on the glued edge and "rub the joint" long ways a few times until you feel the good grip and vacuum seal working. Align the boards perfectly flush and spread glue on the next mating edge and repeat the process until all your boards are together for the panel.

Let them sit like that for a minute or so depending on the temperature. Let the glue start to set a little to prevent slippage when clamping. The rubbing step is very important as well to get the glue to tack.

The key is, after you lay them on your bar clamps, tighten each clamp a very little at a time until they are all snug. This tightening in small increments will prevent any slippage between boards from happening. Check the freshly clamped panel with a straight edge after you have cleaned off all glue squeeze-out with a damp cloth.

Make any necessary adjustment to the clamp foot location with regard to the outer panel edges to keep the glue-up flat while it dries. You will of course have to readjust any board faces that slip out of flush. The panel boards should also be an inch or so longer then net size and possibly the width.

This is a way without special equipment and requires no planing after glue up. If you have a sander like a drum sander, Performax, sanding the boards after planing and before working the edges will give you a better finish and require just a little finish sanding when unclamped.

From contributor A:
You need to own a square square. This can be a typical 12" combo square or a small tri square. However, it has to be very accurate. The Stanley combo square at Homie Dopie is not square.

I suspect that when you are jointing your boards, the jointed edges are not square. Then you glue up and the boards are not in the same plane. Planers are replicators. They copy the bottom of the board and produce the same profile on the top of the board. Most planers have strong enough feed rollers that if a 12" wide board has cup, it may physically flatten it with the rollers. Try taking really light passes with the planer. At the end of the day if your boards are not flat when they are glued up, you need bigger machinery to reflatten. Buy a Starrett 12" combo square if you can afford it ($60).

From contributor L:
The problem with any jointer is that you cannot get it at 90.00. So you need to outthink the problem. If you first flatten the face of board on the jointer, then plane it to thickness, then you are ready to joint the boards. When you put them up against the fence you need to alternate the side you put against the fence. First board, joint with the face against the fence. The next board, joint with the back against the fence. This forms complimentary angles that will add up to 180. If you are off a bit, it doesn't matter - it will still add up to 180. Since I have started doing this, I have very few problems.

From contributor J:
Not sure what kind of jointer you're using, but all the jointers in our shop are able to have a 90 degree fence and hold it there. If your fence is not flat, I'd have it reground so that it is.

From contributor L:
I can get my fence pretty darn close to 90. But to get it perfect is nearly impossible. Same with setting your miter saw to 45.00 - you can get real close, but perfection is nearly impossible. Plus I am not the one having problems getting flat panels.

From contributor R:
Contributor L has got it right. Actually, this is a trick I learned from an old-country trained jointer, when I started out 25 years ago. It was one of the first things I learned that would last a lifetime.

Imagine me, a college graduate, learning basic geometry from an alien on a work visa, with broken English. The information required was as simple as the term "complimentary angles." This was the formula that spawned a lifetime friendship with one of the most dedicated, hard working individuals I have ever met. I had a degree in architecture, he had real world experience. As our friendship grew, we exchanged our knowledge and encouraged each other to excellence. I now own a small woodworking business. My best friend is now a professional engineer involved in solving some of the problems of nuclear reactor containment. Be careful of what you learn. You never know where Knowledge will lead you.

From contributor F:
Yeah, that complimentary angle trick on the jointer is one of the first things I was taught about a jointer. The thing is, it doesn't work for me and the way I work wood. A lot of the species I work have a definite grain direction and when jointing an edge, only one end can be fed forward to the knives without grain tearout. That means the grain direction determines which face needs to be against the fence. I learned that if I went strictly with alternate faces to compensate for an out of square jointer fence, I would get tearout on some edges, which shows in the joint, so I abandoned that practice in favor of adjusting my fence when I am jointing panel edges.

From contributor Y:
Contributor L's method is correct because it eliminates variables. In woodworking there is no such thing as "absolute," but there is "close enough." I know in the purest sense, facing the boards and then planing to thickness, then clamping carefully flat is the ideal. But I would guess that by far, the majority of panels are not done that way.

From contributor F:
True, but the man asked for a method to make panels "perfectly" flat that works without special machinery. I assume he has no carousel clamps or widebelt sander. I am well aware that the method I posted is not production or remotely fast.

From contributor U:
It helps to have a Shelix type head for this, but what I do to get the complimentary angles easily is to lay up the panel after flattening, then flip each stave up on edge the same way. Then run the whole stack on edge across the jointer together, flip it (not end for end, but sideways) to joint the other side. Now they are ready to apply glue and clamp. Making a mark to orient the first stave outside edge (do this before jointing) acts as a reminder for where to start. Very fast and a no-brainer to keep track of.

From contributor M:
I agree that it sounds like your jointer is out of adjustment. Only use precision tools as a guide for setting up machines. What matters is the result, not what the $100 precision square indicates.

With a jointer you should joint two boards and then lay them on a very flat surface (like the jointer's table or a good cabinet saw top). Place them with the referenced face down and push the jointed edges together. Look to see if there is any light or gap showing on the top or bottom of the joint. This works best with thick stock. If you have 4" by 4" soft maple, that is perfect. You can easily see the gaps on thick pieces like that. This will tell you if the jointer is really cutting at 90 degrees.

The same method works on miter saws and table saws. Cut two boards, place them together so that the angles should add to 180 degrees, and look for a gap. This is much better than trying to check the joint with a square.

Like someone else said, a planer will not flatten wide panels. It will only make a consistent thickness (even if it is cupped). The infeed rollers will mechanically flatten the panel before the cutters hit it. Then it will retain its shape as it comes out of the planer.

From the original questioner:
Interesting. I guess I'm doing the steps out of order. I first joint the face and one edge on the jointer and then glue them up and then plane to thickness. But what I'm getting from you guys is to: 1- joint face, 2- plane other face close to thickness, 3- joint edge(s) using the technique that contributor L mentioned, 4- glue up, and 5- plane or sand for final thickness. Correct?

From contributor U:
Yes. Jointing one face only will open it up to a moisture differential that is likely to cause a slight cup in each stave.

From contributor L:
For a good while I was facing only one side and then jointing the edges. But it prevents you from being able to do the complimentary angle trick on the jointer. If you glue up and then plane the same day, you shouldn't have any unbalance issue from moisture. If you wait a few days, you might.

From contributor A:
Contributor L is technically correct in his comp angle method of removing one variable... In most situations we can set up jointers and tablesaws at 90 degrees with a decent square. Contributor L, it sounds like you are having trouble with 90's and 45's. Maybe you should buy a new combo square as well.

From contributor L:
I use a machinist's square. I have no problem with 90's, just doubly sure by doing it this way.

From contributor K:
On some boards, tear out is unavoidable. So what I've been doing after the board is jointed and thickness planed is this... I go back to the table saw with the jointed edge against the fence, I cut just a 32nd off the wild side. Then turn the board around and trim a 32nd off the original jointed edge. This cleans up any tear out and scallops from the jointer blades. It also makes the stock perfectly parallel, and I get accurate 90 degree cuts. The key is to have a sharp blade and a well-set table saw. When running the stock through the saw, push the stock at a constant speed to avoid any flaws. This extra step has made a big difference for me in quality glue ups. Another thing to watch for is a clean clamp. I use the Bessy bar clamps and any old glue on them can cause flatness problems.

From contributor I:
Contributor L is right on. It is easy to knock him for his basic, time tested method. It seems to me to show a bit of arrogance. It's like saying "you don't need a story pole if you would learn how to read a ruler." I try to take as many manmade variables out of my shop as I can. If I don't need a ruler, I don't use one. I check my jointer for square, but flip the boards in case I am out 1/1000 or so. Go back a few hundred years and look at how the masters built. They did not use rulers because mathematically, most were uneducated. They found a system that worked for them. So, regardless of how we get there, if we achieve the same accuracy, who cares? It's all about the journey and learning along the way.

From contributor L:
The funny thing is, I glue up perfectly flat panels... every time.