I have seen websites that sell passage doors that are clad with 1/8 solid lumber on the faces and finger jointed core material below the finish face. I am curious about the straightness and stability of finger jointed core. Would this be a viable material for paint grade cope and stick cabinet doors that ultimately end up with brushed enamel finishes? I am thinking that telegraphing of the finger joints would be masked by the brush stroke. Would a finger jointed stave built out of poplar or soft maple start flat and stay straight enough to be used for a cabinet door with flush inset face frames?
(Architectural Woodworking Forum)
From contributor R:
I've not worked with finger jointed door staves, but finger joints are commonly used on paint grade moldings and trim.
We currently employ a series of relatively simple (but time consuming) steps to produce this door. I imagine that we are one of the few shops that acclimate our lumber prior to milling operations. We cut all of our staves about three inches longer than net and let them air dry for another week before flattening them. Whenever I have discussed this extra phase in the past on this forum I have been soundly rebuked. This has always puzzled me because lumber acclimation is standard procedure for everybody in the flooring industry, but somehow woodworkers think they can avoid this step.
If I built an overlay project, flatness would not be so critical, but with flush inset it really helps.
Some f-j is cut very close to the defect, giving a better yield to the f-j maker and a lower price to the buyer, but a less stable blank than any solid wood can do. I think you would gain nothing, even if this were the only consideration.
The other problem is that the finger joint always telegraphs through the painted finish in time, showing its telltale teeth. It may be a month, or a year, but with a few humidity cycles, it will show up. This would certainly be considered a defect by all but the very least discerning buyers.
As for your cut 3" over the finish length and sticker, I think you can do better. First, why 3"? Why not 3/4"? Do the math, and you will see the yield go up. What are you going to lose? The blank is not going to shrink in length, is it? Secondly, why not flatten through a first head jointed S4S machine to 1/8" over dimension (I'm assuming you are talking cabinet stiles and rails), then sticker it for a while, then back through the S4S the final size and flat? Or power feed over a jointer, then through S4S oversize, age, joint again, then final S4S?
I think the stickering for a week is fine, but you have to realize that basic science can evolve into magic or myth. If you do flush inset doors, and you have so many problems with hardwood staying flat, I'd look closely to your lumber source and your shop temp and humidity well before exorcising the demons in the wood pile. Voodoo ain't the answer.
I can appreciate you looking for a better material; however I think you are barking up the wrong tree. If you want more stable wood, try to get some quatersawn product. Jointed/faced well dried wood should stay pretty flat.
The idea of letting your material sit and acclimate is certainly up for discussion. The acclimation should be geared towards its final home for your flooring example to be true. Allowing material to acclimate to my shop has nothing to do with the house it's going to be sitting in two weeks from now.
The face frame stock and the door stock should come from the same pile. I would hesitate to pull some wood off the rack and mix it with some directly from the lumber distributor. If anything, my rack wood will be wetter than the lumber distributor. If I was planning on mixing batches, I would allow a couple of weeks to acclimate new stock.
I cannot imagine trying to get a first class paint job on finger jointed stock. Telegraphing of glue lines, different wood densities, edge grain vs side grain. It's not going to be pretty unless you bury it under a coat of Bondo.
Please describe your previous cabinet door problems. I'm not trying to be critical. I've never heard of anyone proposing your method of construction. You might take a look at finger joint trim down at the lumberyard... It ain't pretty.