A stable table top starts with the right knowledge.
Restaurant quality wood table top construction is harder that it looks. While the table top is simply a glued up block of wood, it must be manufactured in a very specific way to create a durable surface. The hospitality industry is notorious for being hard on wood tables, so extra effort must be considered in all aspects of construction, from milling and board selection to the finish. Here are some of the aspects that go into the construction of a wood restaurant table.
In order to make wood stable enough for furniture, it must first be kiln dried. The main purpose of kiln drying lumber is to remove excess moisture so the wood stops shrinking when it is dry. Other advantages of drying your lumber in a kiln is to eliminate any bugs that may be living in the wood and to solidify any pitch that may be present. Once the lumber is kiln dried to 8% moisture content, it is considered to be furniture grade for a tabletop.
Grading the wood
Choosing the right grade of wood for a restaurant table is also a very important aspect of the construction. Different species of wood have different grades, and you need to know the difference in order to select the boards that will perform best for your application. Flat grain and vertical grain perform differently. There is more expansion and contraction in flat cut lumber, while vertical grain tends to be more stable but has a less interesting looking grain pattern. The grade we use is called Free Of Heart Center, or FOHC. The heart of the tree, called center strike, is usually prone to cracking and is not suitable. Selecting boards that are free of center strikes is another consideration to think about when choosing wood for a restaurant table top.
Straightening edges- Sawing
Once the wood has been kiln dried to a furniture grade, the individual boards need to be straightened in preparation for molding. This edge work is done with two machines; a gang rip saw and a molder. The Gang rip saw is like a very heavy duty table saw, but has multiple blades. These blades can be set a specific distance from each other. When a crooked board is put through this machine, the parallel blades straighten out the board. This process makes it easier for the second machine to process.
Straightening edges- Molding
A molder is a high-tech version of a planer, but it has multiple heads on all sides. The purpose of putting the wood through this machine is to create four edges that are perfectly square and parallel with a very fine cut to them. The wood that goes through the molder is slightly rough as it goes in and perfect when it comes out. We use very precise machines to mill the lumber because it makes for a an easier glue up and a more stable table.
Rotating the grain direction
It is said that it takes 10,000 hours to become an expert at anything. Only after that amount of time will you have seen all of the issues that can occur and know how to handle them. Some of the things we learned very early on the way to becoming expert table makers is that you must alternate the grain direction of each plank in a table. This is especially critical when using flat grain lumber. The alternating grain pattern counteracts any seasonal movement from becoming pronounced and helps with the dimensional stability of the table.
Dry-assembling the planks allows our craftsman to make sure the grain orientation is correct, and that the table looks good before it is assembled. Think of dry assembly like a preview. You can correct aesthetic elements that we might find distracting, which creates a more balanced look. The loose boards are easily transferred to the clamps for gluing in the exact same order. This helps with eliminating mistakes and costly rework.
The most widely acceptable glue used in the construction of wood tables is Polyvinyl Acetate, or PVA for short. PVA glue is a food contact friendly adhesive that forms a tight bond between two pieces of wood. This type of glue has no added formaldehyde so it complies with CARB2 standards. PVA comes in a variety of types, from fast setting glue that you can handle 30 minutes after application, to types that have long open times for elaborate construction projects. These long open time glues are typically used when the weather is hot and you don’t want the glue to setup before you bond the two pieces of wood together.
Successful glue-up starts with a good clamping system. You want even pressure across the entire length of the boards. You also want the right amount of pressure to make sure the glue is perfectly in contact with both sides of the wood you are gluing. Too much pressure and you will squeeze all the glue out; too little and your table will fall apart. There are many ways to apply pressure to wood during the gluing phase. We use a machine called a Taylor Carrier Clamp. This machine was made for edge-gluing parts together.
There are other ways to achieve the same goal; pipe clamps and bar clamps are the most common. All clamping systems do the same thing; put pressure on the edges of wood to bring them close enough so the wood glue has time to set up. The most high tech version of a gluing machine uses hydraulic pressure to clamp the wood, and microwaves to cure the glue in seconds. This machine is called an RF (Radio Frequency) press. It is used in high volume shops for repeated parts that are the exactly the same size.
A large sanding machine is typically used to clean up the tabletops once the glue is cured. We use a combination planer-sander that takes off more material so that we have fewer passes through the machine. If you only have a small sander, it will take more labor to flatten a tabletop and get rid of all the glue squeeze-out left over from the clamping process. To flatten a tabletop, feed one side of the table through your sander multiple times until you see no more glue squeeze out. Once you have a perfectly flat back, you flip the table over and start sanding the face of the table. You are trying to eliminate glue squeeze-out and make all of the tables a uniform thickness. This ensures that all of the tables from a batch are the same height. The final sanding of the table uses a fine grit so the true depth of the grain is revealed.
Cutting the table to final dimension is done with a large sliding table saw or a panel saw. Both of these types of machines excel at this type of cutting and are very accurate. Once the tables are cut to the customer’s dimensions, our craftsman adds the final edge work detail to the tables. This process includes using a hand operated sander to smooth out the edge grain and a hand-held router to ease all of the sharp edges.
After all of the hand work is done, the table is ready to go to the spray booth for multiple layers of conversion varnish. Our conversion varnish has been tested to withstand Ecolab cleaners along with a host of other corrosive things like bleach rags, alcohol, citrus, mustard and wine. For a detailed explanation of why conversion varnish is the best finish for restaurant grade table tops, read our article on Finishing Wood Restaurant Tables.
One critical aspect of finishing any tabletop is making sure the underside of the table is finished with the same number of coats as the top. If one side has more finish than the other, then the ambient moisture will seep into one side of the table more than the other and cause the table to slightly warp.
After countless hours working on the tables, the last thing we want to happen is have the tables get damaged during shipping. We take the time to wrap each table individually in foam cushioning to protect the finish. We then carefully crate the entire table top order in plywood and put protective corners on to make sure the tables get to you in one piece.
We have a great working relationship with several national carriers, so you can be rest assured that you will get the best shipping rates and quickest transit times.
Watch the Video!
If you are still curious about how we make our tabletops and want to see our shop, check out this video we made especially for you!