Hello all…
Recently my partner and I ran into the following problem for door and drawer front construction:
These doors are black walnut and go into a kitchen and bar and are inset. The spec is a slab door with grain running horizontal, with the face being hardwood strips approxiamtely 4.5″ in height and running to the outer edge of each door; where each strip meets its neighbor there is a 1/8″ (wide) x 1/8″ (deep) dado. We made a sample door about 2 months ago. Our construction went as follows: 1/2″ mdf wrapped in 1/2″x1/2″ hardwood edgeband, phenolic back walnut veneer on the back attached with Wilsonart 700 series pressurized contact adhesive system and 1/4″ thick hardwood strips affixed to the face with titebond III. To get the dado we just made saw kerfs at each of the strips edge joint. The punchline is that the door is warped 1/2″ in 28″ of run longitudinally and 3/16″ in 12″ of run laterally, like a pringle or a saddle and the longitudinal warping (1/2″) was torward the hardwood, while the lateral warping (3/16″) was toward the veneer.
My question is: how should we build this slab door so that it does not warp?
Some possibilities we have thought of:
1. 3/4 walnut plywood with edge banding and saw kerfs 1/8″x1/4″ with 1/8″x1/8″ inlaid walnut in the dados.
potential problems: see the plywood edge on each kerf, durability, does not give the grain variation the client wants; it would essentially be matched in 8′ runs.
2. 1/4 plywood (mdf core) with 1/4 hardwood on each side, dados on front only. hardwood affixed with titebond III.
potential problems: may bend towards kerfs, like relieving something for a curve. it may be very difficult to get the door flat.
3. solid hardwood with harwood runners on the back.
potential problems: The obvious problem is wood movement, not to mention the unsightliness of the runners on the back.
4. 1/2″ door frame assembled with dowels and 1/4″ harwood strips affixed to the front with titebond III. Possibly rabbet in a 1/4″ back.
potential problems: back is either open or shows seam where 1/4″ meets frame. will the frame hold the hardwood on the front in check?
Please advise….
Thanks in advance for any thoughts.
Edited 2/28/2008 9:57 pm ET by Markansas
Edited 2/28/2008 11:15 pm ET by Markansas
Replies
Those 1/8" dados are a killer for the veneer ideas. I like to keep shop made veneer a max. of 3/32 thick although others say 1/8 is OK. (I've had failures at 1/8") In that light, I'd simply make these doors out of solid wood, dado both front and back to keep them balanced. You will have significant crossgrain movement (expansion/contraction) in solid wood so you must allow for that in the way the doors are mounted.
In any case, you must strive for a balanced construction. Your first attempt that you described is far from balanced. Additionally, you used contact cement to affix the veneer. This adhesive does not lend stability to veneer. It's fine for plastic laminate, but not for wood.
Alternatively, use regular flitch veneer on both inside and outside, dado both faces through the veneer and into the mdf. Then either dye or paint the dados a dark color. This isn't what they want, but sometimes we can't have what we want and must make compromises.
would it not make sense that slab doors should be made of slabs,or at very least solid wood? you have way to many things that need to breath samwhiched together and the mdf is loosing and always will . try solid lumber and switch you grain direction on each peice, also I would try to keep the thickness around 1". plus all end grain must have up to twice the finish applied. maybe if there we had a pic to look at there may be other advice.
the Woodbug Dan
About a year ago our shop made a large number of cabinet doors looking very much like you describe. The project involved doors of sapele, wenge, and white oak. We made them the following way:
Using a core of 1" MDF(28 mm)we inlaid strips of 3/8" x 3/8" solid wood, across one face of each full 4x8 sheet, at the places which would later get the 1/8" saw kerfs. After gluing in these strips we let it dry completely for a few days, then ran the full sheets through a wide belt sander at 120 grit to be sure it was perfectly uniform and without hills or valleys. We then glued 0.6 mm veneer to both sides of the MDF core, grain parallel to the strips. The sheets were then cut up into individual doors, maintaining grain continuity where it was necessary. A tablesaw with scoring blade is essential. Each door was edgebanded with veneer on all 4 edges. Finally, the 1/8" kerfing was done on the outer face of each door, cutting into the solid strips that were embedded under the veneer.
All in all, rather painstaking. But I had occasion to visit the job last week, and the doors are in fine shape.
David Ring
http://www.touchwood.co.il/?id=1&lang=e
Mark,
Traditionally, board and batten doors are made with the face boards tongue and grooved together, held together by a pair of parallel battens attached to the back (screws, or sliding dovetail), and kept from racking or sagging by a diagonal batten running corner to corner between the parallel ones (looks like the letter "Z"). Each board can then swell and shrink individually, without greatly affecting the overall size of the door.
Ray
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