How Mitered Cabinet Doors are made

This video shows many of our replacement kitchen cabinet doors.

One of our computerized machines, shown at top-left, cuts the perfect 45-degree miter and routes the mortise and tenon for our invisible, industry-leading mitered door joining method.

At bottom-right we demonstrate the assembly of this joint and show how the invisible mortise and tenon produce the tightest and strongest mitered assembly method in the industry.

All mitered cabinet door manufactures will eventually be using this method but, as of January 2016, we are the only manufacturer offering mitered doors online with this level of manufacturing quality.

A few of the kitchen cabinet door styles we manufacture can be seen as these doors move past. Several stop and expand and those doors are mentioned by door name.

The first of these doors is the Woodhaven, at top-left. This cabinet door is shown in Red Oak.

Next is our Vermont door, shown in Select Alder.

The Vermont is followed by our Manhattan door, in Select Maple.

Next is our Camden, shown in Alder and finished with Minwax Stain.

Our Bellingham, shown in Maple is an applied Moulding cabinet door.

The Delaware cabinet door is shown in Alder.

This Ponderosa door is also shown in Alder, which is very similar to Cherry in appearance.

Next is our Sheffield cabinet door shown in Maple (sometimes called hard-rock maple).

Our Malibu door is of Hickory and some call the color variations in hickory “Calico Hickory”.

And this Danish kitchen cabinet door features the simple, uncluttered look of its sister door, the Cope & Stick Shaker door.

Each of our replacement kitchen cabinet doors in the Mitered styles are available in all woods and in any custom sizes above the minimums.

Glass Frame Cabinet Doors…How they are made, how to order, and how the frame is machined to allow glass to be easily installed

This video explains how glass frames are made as well as how to order them online and how the frame is machined to allow glass to be easily installed.

If video above doesn’t open, Click here for the video…

This video will explain the difference between standard cabinet doors and Glass Ready cabinet doors. Continue reading

What is a Mitered Cabinet Door and how are they made?

As I explained in the post “What is a Cope and Stick Cabinet Door and How are They Made?”, there are two major categories of Cabinet Doors. These are Solid Slab, or plank doors, and 5-piece doors.

The Slab door is simply several boards edge-glued and trimmed to the desired size.

5-piece cabinet doors are divided into two design categories; Cope and Stick and Mitered.

The 5-piece door is more complex but more reliable and more pleasing in appearance. This is especially true with Mitered doors which offer more moulding choices than Cope and Stick designs.

This post is focused on the Mitered, 5-piece cabinet door.

The drawing below shows a Cope and Stick Cabinet Door and Drawer Front on the left and a Mitered Cabinet Door and Drawer Front on the right. The differences are in the corners and the method of joining the parts of the frame.
The Mitered door has the frame joined at a 45-degree angle while the Cope and Stick door frame is connected at a 90-degree angle.

The five pieces in a Mitered door are the four parts of the frame, called Stiles and Rails. The Stiles are the vertical pieces, or sides of the frame and the Rails are the top and bottom pieces. The fifth piece of the 5-piece door is the panel, which the frame surrounds.

The reason the 5-piece door is more reliable than the Slab door is in the way each design responds to changes in relative humidity.

All woods will expand as humidity increases, and as humidity decreases they will contract. An average width Slab Cabinet Door, being between 14 and 20 inches wide, will expand and contract with humidity cycles over the year by as much as three-sixteenths-inches. Some wood types react more and some less, but three-sixteenths-inches is typical for a Slab door.

While this may not sound like much, it is enough to prevent butt-door pairs from closing during high humidity times and cause a gap between the butt doors of one-half inch in low humidity times.

Here is where the 5-piece design comes to the rescue.

In the 5-piece door the panel is allowed to float within the frame, so during panel expansion the panel edges simply move deeper into the Stiles and during contraction the panel slightly pulls back. The Mitered door is designed with a groove for in the stiles so panel movement is accepted without being noticed.

The top drawing shows an end-view of the stile with a contracted wood (low humidity) panel, while the drawing below shows a humidity-expanded panel. Notice that the panel still reacts dimensionally with changes in humidity but in the 5-piece door this panel movement is absorbed by the groove in the stiles. This design keeps the overall width of the door constant as the relative humidity fluctuates.

With Mitered doors there are several joining methods used across the industry. The newer methods using computerized machinery are more reliable and far more accurate. The blind mortise and tenon method produces an invisible joint that is both stronger and more resistant moisture than earlier joining methods. An example of this blind joint is pictured below.

Mitered Cabinet Door Joint


Blind Mortise and Tenon Mitered Cabinet Door Joint 


Shop For: Mitered Cabinet Doors

How Replacement Kitchen Cabinet Doors are made

Basically there are three designs if cabinet doors; these are Slab (or Plank), Cope & Stick and Mitered.
Slab, or Plank doors are simply edge-glued strips of wood. Slab doors are very susceptible to warping and twisting caused by variations in humidity. Most cabinet door manufacturers don’t offer Slab doors for the reasons stated, but some small, local cabinet makers still make this door style. Sometimes “look-alike” Slab doors are made of laminated MDF (Medium Density Fiberboard) and offered as Slab doors. These doors overcome the slab’s tendency to warp but have a plastic-like look along with all the negatives of MDF.

Cope & Stick doors are the oldest of the 5-piece cabinet door designs. They have been manufactured for several hundred years and are still popular today.
Cope & Stick doors consist of a frame made up of two stiles (the vertical side pieces), two rails (the horizontal top and bottom pieces), and the center panel. Those two stiles, two rails, and panel make up the components of the 5-piece cabinet door.
By using various machining methods and cutter profiles Cope & Stick doors can be manufactured in literally millions of design variations. A large door manufacturer may have 40 different Stile Cuts, 40 Panel Cuts, and 60 outside edge designs. When multiplied by several hundred different style possibilities, twenty wood types, and the various arch possibilities, the permutations multiply to many millions of unique door designs.
The most recognizable of the Cope & Stick door designs from the 1700’s is probably the Shaker Cabinet Door, which is actually still very popular today.

Mitered Cabinet Doors are also 5-piece doors with a different method of attaching the stiles and rails. Mitered rails attach to the stiles at a 45-degree angle, while Cope & Stick stiles attach to the rails at a 90-degree angle. Examples of Cope & Stick and Mitered cabinet doors can be seen on our site, CabinetDoors.Com.
With the invention of computer controlled mitering machinery, mitered doors have dramatically increased in dependability and popularity. Computerized machining allows for a mortise & tenon joining method that produces mitered joints that are as durable and tight as cope & stick joints. This dependability improvement, coupled with the greater design options have accounted for the steady growth in mitered door popularity.
Today, properly machined mitered doors are even more sturdy and reliable than cope & stick doors. Also, because of the increased productivity provided by the CNC Mitering machinery, mitered door prices are now equal to, or lower than comparable cope & stick doors.
See the CabinetDoors.Com Blog.

New Machinery At The Door Stop


New Coping Machines

New Coping machinery arrives at The Door Stop

Along with new Triple-head Widebelt Sanders and additional CNC Mitering machinery, The Door Stop has added two additional Cope & Stick Coping Machines.

Accuracy in Coping is essential in hi-quality cabinet door manufacturing. Accurate and tight-tolerance copes make for exceptionally tight joints and are necessary for the widebelt sanding operations that follow. Without highly accurate copes the sanding operations will remove unequal amounts of material across the face of the door, not allowing the successively finer widebely grits to completely remove the scratch pattern left by the prior sanding belt.
Continue reading

Moulder Knife Marks Per Inch

Proper Moulder operationImproperly set moulder feed rates can cause a Washboard finish that is often invisible until stain is applied.

Here is a table published by Wisconsin Knife Works, Inc. summarizing the results of their study on the number of knife marks per inch required to produce a stain-ready finish on various wood types.
This table shows the Knife Marks per Inch ranges generally recommended for wood species commonly used in manufacturing Cabinet Doors. Continue reading

Accurate Sizing & Humidity Effects

Our cupboard doors are accurate to within 0.015 inchesThere are three key steps in manufacturing 5-piece Cabinet Doors that will determine the sizing accuracy of the finished door. If each of these steps is held within a tight tolerance, the finished product will be accurate to within the desired 1/64 inch, or about 15-thousandths.

The first of the three critical operations is moulder accuracy (sometimes americanized as “molder”).
The second critical operation is stile & rail length cutting accuracy and the third is consistency in stock removal during the operation of machining the outside edge.
Our standard is to hold each of the three critical operations to a tolerance of 5-thousandths of an inch. This produces a finished cabinet door with a worst-case sizing tolerance of 15-thousandths, of 1/64-inch.

The stile stock moulding operation starts the process of insuring sizing accuracy and, without close attention to this step, consistency in sizing the finished door is almost impossible.
When cabinet door stile stock is moulded, the width of this stock is the most critical factor in accurately sizing a 5-piece cabinet door. If the moulded width of the stile stock is held within a tolerance of 5-thousandths of an inch, the subsequent operations that affect sizing can be standardized.

At CabinetDoors.Com length cutting of stiles and rails is performed on CNC machinery so achieving our 5-thousandths tolerance for this operation is actually easy. Cutting accuracies of better than 5-thousandths are normal.
The outside edging operation is more difficult to hold because the edging cutter’s diameter changes from sharpening, so slight variations do occur. Our average edging tolerance does achieve the 5-thousandths inch goal, but the standard deviation shows a range from 2-thousandths to 9-thousandths inches.

Because the moulder accuracy is key to finished door sizing, let’s look at some examples of inaccurate moulder adjustment and the effects these errors will have on the finished size of a 5-piece cabinet door.
First let’s assume the moulder is set up correctly and the stile stock, which is targeted at 2 1/4–inch width, is actually oversized by 5-thousandths (2.255 inches). Assuming the rail length cutting and the edging operations are both perfect, the finished door will be 10-thousandths oversized. Most cabinet makers will be measuring the cabinet doors with a tape-measure, so the 10-thousandths error on this door will be considered perfect and within the acceptable range of even the most demanding cabinet professional.
Now let’s assume the moulding operation is not within a width tolerance of 5-thousandths and is actually over by 15-thousandths of an inch. That will make the stile width 2.265 inches, with the additional 15-thousandths doubled to 30-thousandths by the same error in each of the two stiles. This door will be oversized by 1/32 inch even if the other critical sizing operations are perfect.
This 1/32-inch error, while acceptable by the standards of the industry, is detectable with a tape measure.

The challenge to the cabinet door manufacturer is to size the door as accurately as possible by setting tight measurement quality tolerances on the operations that affect door sizing.

The variable beyond the control of the manufacturer is the normal swing in relative humidity and the effects humidity changes will have on the moisture content of the wood in the doors. All cabinet doors will react to changes in relative humidity by either absorbing, or giving-off moisture. Unfinished doors will react sooner to humidity changes, but even properly finished doors will eventually reach a balance between the relative humidity and the door’s internal moisture content. These moisture content variations will result in dimensional changes to the stiles and rails of the cabinet door.
These dimensional changes can be huge and are usually far greater than the total manufacturing sizing tolerances.
The definitive study on humidity and its effects on wood moisture content, and the changes it causes to wood dimensions was conducted by the US Forest Service, a department within the US Department of Agriculture.
The Forest Service, published the Wood Handbook: Wood as an Engineering Material in 1999 (and 2010), which outlined the expected moisture-content caused dimensional changes in various woods. The 1999 study focused on wood flooring but applies to all wood products kept inside the house and subjected to normal fluctuations in relative humidity. The 2010 study is extensive and covers almost all commercially used woods.
The 500+ page 2010 study can be viewed or downloaded here (Chapters 4 & 13 deal with Moisture and expansion properties)…

I’ve tried to simplify the findings by focusing on plainsawn (Flat Sawn) Red Oak for this example. But, woods other than Red Oak and differing sawing-grain directions, like quarter-sawn, have different Coefficients for Dimensional Change. Because plainsawn woods are more popular and tend to have a greater dimensional reactions to moisture variations, I have used plainsawn in my example.
The bottom-line finding of the USDA research is that a 4% change in the moisture content of the 2 ¼-inch stile of a 5-piece Red Oak cabinet door will be expected to cause a dimensional change of 0.0332 inches, or about 1/32-inch, per stile. That means that a 4% change in moisture content is expected to expand, or shrink the width of a 5-piece Red Oak cabinet door by 1/16-inch, which dwarfs the 1/64-inch worst-case tolerance of the cabinet door as it finishes the manufacturing process.
This 1/16-inch moisture-caused change is 4-times the combined total tolerance of the critical steps in the making of a cabinet door, and certainly needs to be considered when designing cabinets. This is especially true when considering the spacing between butt-doors on cabinets. Without proper spacing, butt-doors may not close properly during high humidity periods.

These humidity-caused sizing swings may seem extreme, but keep in mind that these calculations reflect the humidity of the worst-case the country has to offer; the desert regions of the southwest. In the southwestern deserts relative humidity routinely changes from 5% in the dry month of June, to over 90% when the monsoon storms come in July. This wide humidity swing accounts for the 4%+ change in the moisture content of wood products in the southwest. Cabinet doors installed in other parts of the country will typically be expected to experience about half this dimensional change, or about 1/32-inch.

Design provisions to accommodate dimensional changes in the raised panels of cabinet doors are in place allowing the panels to float within the stiles and rails. The panels used in recessed panel doors are either Medium Density Fiberboard (MDF) or MDF core with wood veneers, which are dimensionally stable and react very little to humidity changes.

Looking at the once popular, and hopefully never to return to popularity, Slab Cabinet Door as an example , you can see the makings of a dimensional train-wreck. With the Slab Door we are not just dealing with the moisture-related dimensional properties of a 2 1/4-inch stile. We are now looking at the dimensional properties of a glued-up slab between 12 and 24 inches wide.
Using the same moisture-content calculations for plainsawn Red Oak from the Forest Service Study, we would expect to see a 12-inch wide slab door react to a 4% moisture content change with a width change of over 3/16-inch and a 24-inch slab changing width by over 5/16-inches.
Clearly width changes of these magnitudes are unacceptable and homeowners requesting slab doors need to be made fully aware of the dimensional instability of this cabinet door design.

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