The glass doorframes should be made out of solid wood. Materials such as particle board, MDF or other manufactured materials will not hold edges in the same manner as wood. Good choices for cabinet doorframes are hardwoods such as oak, cherry and maple. However, pine is often used. As a softwood, pine is easier to work with.
The negative of using a softwood for a glass doorframe is the weight of the door and the holding power of the hinge screws. Glass cabinet doors are heavy, and hence apply a great deal of bending leverage to the hinges and the hinge screws. Softwood lumbers do not hold screws in position as well as hardwoods.
You must first decide if you will have the doors mount to the inside or on the outside of the frame of the cabinet. There are two types of cabinet framing, frameless and framed and each of those has two possible mounting methods, overlay and inset.
Additional information on frameless, framed, overlay and inset doors.
The first step in making the glass doorframes is to cut the lumber to width and length. In many cases you will be able to purchase the lumber in the correct width, 2″ to 3″ works well and the exact width of the frame is not critical.
If you are ripping the lumber to a specific width it is best to sand what will be the inside edge, before cutting the pieces to length and definitely before gluing the pieces together.
Figure 11 - Miter saw
Cut the pieces to length, remember that the accuracy of the square joint is critical to the final appearance of the door. A properly setup miter saw (Figure 11) or radial arm saw works well to cut the lumber to length with a perfectly square end. The key here, is that the saw is properly setup!
Remember that if you are making mortise and tenon joints, that the lumber must be long enough to accommodate the construction of a tenon on the ends of the pieces. If you are making lap joints, the lumber pieces must be long enough to accommodate the overlap.
Once the pieces are cut to length, cut your tenons, mortises, install biscuits or place dowels as the case maybe. Dry fit all pieces together before proceeding any farther.
One of the biggest mistakes that a home handyman will make, when building a glass cabinet doorframe, is not to ensure that it is perfectly square. Frame deformity usually occurs during the process of clamping the joints while the glue dries.
To avoid having the frame twist or bend out of square it is best to create an easy frame gluing jig. Measure the inside of the largest door and cut a piece of plywood, at least a 1/2 inch thick to those dimensions. Ensure that the piece of lumber is perfectly square. Screw that piece of lumber to another piece of plywood or directly to the workbench. Build your frame around this piece of lumber as shown in Figure 12.
Figure 12 - Cabinet doorframe gluing jig
Figure 13 - Web clamp
Note: It is best to make the jig to conform to the inside dimensions of the largest door first. That way you can cut the jig down, as the door sizes get smaller, rather than cutting new pieces of plywood or other material for each size door.
Figure 14 - Bar clamps
Once you have checked the door for size and square, you can take the pieces apart and using yellow carpenters glue (do not use the white wood glue), glue them together.
Use a web clamp (Figure 13), or bar clamps (Figure 14) to hold the sections together, on the jig (Figure 13 does not show the jig) until the glue dries thoroughly, usually overnight.
After the glue has dried thoroughly you an use your router to make a 3/8 inch rabbit on the inside of the frame. The rabbit should leave approximately 3/16 inch to a 1/4 inch of material to provide a lip to hold the glass, as shown in Figure 15.
You can leave the lip square, as shown in Figure 15 or use a 1/4 inch round over router bit to create a slight roll on the lip, as shown in Figure 16. You can also use your router to round off all of the sharp edges of the doorframe.
Note: If you are going to round off the edges of the doorframe it is best to make all the doorframes first and then setup your router with a round over bit and do all the doors at one time. This will ensure that the round over is identical on each door.