Flat Faces on Shop-Built Doors

An exchange of views on lumber handling, door assembly, tolerances, and the meaning of "high end." June 18, 2005

I have a small 2 1/2 person shop. We do 1 - 2 kitchens a month. I have an area for making doors that uses Jorgensen cabinet clamps for assembly. On larger doors I occasionally have the problem of the door coming out less than flat, a bit like a potato chip. Does anyone have suggestions to avoid this?

Forum Responses
(Cabinetmaking Forum)
From contributor F:
Pretty easy, really. The door glue up bench must be reasonably flat. The bar clamps must be fairly straight. The door parts must be fairly straight. The joints must be at 90 degrees exactly. And lastly, the assembler must check the top of the door with a straight edge to make sure the clamps aren't tweaking the stiles up or down in relation to the straight plane of the rails. If they are tweaked, it can be corrected with a block and mallet if they are kicked up, or by loosening the clamp pressure if they are pulled down.

From contributor P:
Are you buying your hardwoods rough or surfaced? Make sure you are flat joining all of your stock. Try to pick straight grain also for the larger doors. Every little bit helps.

From contributor F:
As far as face flattening stock on the jointer, I am a furniture maker, too, and I can't even work a board unless I have flattened it first... but I have worked in production shops in the past and there is no time for that. I have a friend who makes cabinet doors for a living and I'll guarantee he doesn't flatten stock. He buys .8125" S2S1E. As soon as it comes into his shop it goes straight to the table saw and he rips it to stile and rail width and from there it goes straight to the shaper. His doors are as good as most production door makers.

From contributor P:
All of our stock is brought in rough. I would never buy surfaced material unless it was for moldings in long lengths. Another plus is we do all inset doors on our built ins and use 7/8-1" thick doors.

I think some of the guys that do kitchens have tons of problems because of doing fast production work and forgetting to do the basics in woodworking. Doors out of line, warped, panels cracking, etc. And then the business side of it - not getting paid, customers not happy, etc. We never have these problems. I feel sorry for the guys that do these kitchens because they start to compete against a market that is so tight they sell themselves short on jobs and end up losing. Most shops are really not set up for woodworking, only for cabinet assembly. I know guys that only have a tablesaw and a drill press and tons of battery drills to put all of the outsourced cabinet parts together. I wonder if they have these problems because the customer thinks a real woodworking shop is making their cabinets in this shop and then they end up with the same thing they saw at Home Depot. Oh well, glad to see I am not the only one that flattens wood still.

From contributor F:
I do the same as you in bringing in all my stock in the rough. The side benefit to that is being able to net some thicker material when the boards aren't bowed too badly. That lack of a jointer in a lot of wood shops is amazing. I don't know how anyone works wood without one.

A friend of mine is one the fastest I have ever met at cutting a set of cabinets and also assembling them. He rips S2S1E and then chooses the straightest material for his longest parts. Whenever I mention a jointer to him, he holds up his hands and shows me that he has all ten fingers. He has table saw methods of straightening a board edgewise and says that the straightness and stiffness of the carcass members will take care of face bows.

From the original questioner:
Thanks for the help. Contributor F, we follow most of these procedures now, but I suppose we just have to be more careful with our stock selection.

As far as flattening stock, that's the first thing I do if I'm making a piece of furniture. But when you make 30 doors for a kitchen, it doesn't make economic sense. It is quicker to make a new door if one comes out skewed. I appreciate the attention to detail, though. All our kitchens are high end, and I like to combine the production mentality with the quality mentality. It is often a bit of a balancing act.

From contributor F:
Do not underestimate the importance of a flat assembly table or a simple check with a straight edge. One thing I learned when laminating boards face wise is that if you clamp them up on something straight and rigid, when the clamps come off, you have a straight glue up.

From contributor T:
When you crosscut a plank to make parts for a door, this is the first time that end grain has ever seen daylight. The board is going to either add or lose moisture until it reaches a happy balance with ambient conditions. If you allocate your lumber staves about four inches longer than final net length, and let them air dry for a couple of days, you will get flatter doors. It is pretty much standard fare for a hardwood floor to acclimate before it is installed on a job site. For the same reasons, it is a good idea to let your wood acclimate in your shop before you attempt to flatten it. This policy seems to work for us. Your mileage may vary.

From contributor R:
I clamp my doors with bar clamps and lay my clamps down flat, so the bar is running along the top and bottom edge of the door, preventing the door from cupping up. They sometimes cup from the tongue not fitting the groove real tight. Even laying the clamps down flat, if they are over-tightened they still cup up like a potato chip. If they happen to cup up (with the door on a flat surface, you can see light under the rails) and stiles are hitting table top, I roll with the flow, and let the drum sander solve it.

As for the jointer, I do have one, but I only use it when I need to. I don't have a set rule that says all stiles and rails are to be run through the jointer. My lumber comes in 13/16ths, straight-lined one edge. I sometimes use the jointer when gluing up panels when the lumber is too bowed to pull up a good glue joint.