Tabletop Glue up Techniques
|When building furniture you will need to make a top either for a
table, small coffee table, nightstand, dresser, buffet or other types of furniture. To create a wide surface, boards must be butted
edge-to-edge and glued. When doing big
tabletops this can be a bit of a challenge.
A well-made top is mostly the result of the following tried and true steps. These techniques can be used to make any surface large or small.
When you start you will want boards that are a bit thicker, wider and longer than necessary. To reduce the warping your boards should be given time to acclimate to your shop temperature and humidity. They should be stored flat with stickers between then for at least a week. If you are using rough sawn material flatten one face on the joiner and square one side before running through the thickness planner. Then rip the rough edge on the table saw. We have found that the Freud Glue Line blade does a very good job for a clean edge. If your material is already planned to size just join and square the edges.Once the boards are flat and straight, lay them out. To create a top that looks good, you need to consider the grain direction. We always try to layout the boards with the heartwood side up if possible. The heartwood side of the board is the one that faces toward the center of the tree. Boards tend to cup away from the heartwood side when they dry. When making a top of many boards it can affect the flatness of the panel. For a top that is secured to the base it is a good way to ensure that the top stays flat.
If you alternate the heartwood sides some up some down the panel will stay relatively flat across the entire width. However, it can result in a washboard effect. Once you have decided on the best lay out for the boards mark them with either a soft pencil or chalk. We have found that a large triangle works very well in the center of the top and edge-to-edge. We have used a DeWalt Biscuit joiner to help align the boards during the glue up and add extra strength to the project. They are normally spaced about 8/10 apart. Be sure to center them in the boards and stop so that they will not be exposed on the ends.
With all the boards flat, and arranged on your table top you are now ready to start thinking about the glue up procedure. You need to make sure that your tabletop for glue up is flat. An uneven or twisted work surface means that the clamps will not be in the same plane and could cause a twisted top. We use our tablesaw table and extension table for small glue ups and our Acorn Work Benches for medium sized tops and a fabricated 4 x 8 table for large glue ups.
You are now ready for a practice run. Depending on the size of the glue up it may require two people. Yellow glue (aliphatic resin glue) sets in about five minutes at 70 degrees or less. All of your clamps should be laid out and we have found that Jorgenson ¾ pipe clamps work very well for larger glue ups. They are very stable and not easy to knock over. On large glue ups your clamps should not be spaced more that 16 apart.
Keep in mind that you need to alternate the clamps, one on top and the other on the bottom. Clamp all together and review the glue lines. If you see a large gap, rather than putting more pressure on the clamps, remove the offending board and run through the joiner again.
When all the boards seem to align it time to start gluing. Re-arrange all your clamps, align the boards, biscuits if need and an old credit card. Everyone gets these plastic cards in the mail and you should save a couple as they make the very best glue spreaders. Apply glue to the entire edge and then use the card to spread it. Slide the boards together with the biscuits in place.
Check the underside of the top to make sure that it is sitting flat on the clamps and if not, hit it with a hammer and a block of wood to fit. Starting at the middle of the top and working towards the end begin applying additional pressure to the lower clamps. If any of the boards are misaligned mount c-clamps at the ends of the top across the joint that will not align. Apply additional pressure to the end bar clamps and then remove the c-clamps.
Always the pressure from the clamps will cause the glue to spread from the joints. Once the glue hardens it is a chore to remove. To make it easier, allow enough time, usually about 15 minutes, for the glue to turn rubbery. Using a flexible putty knife, scrape off the glue.
Allow your project to set overnight to assure a strong bond before removing the clamps.
Check the top with a straight edge and mark any high spots with a soft pencil or chalk. You can use a jackplane to level the high spots. Once you have removed the marks check the top again and mark as needed.
If your project is small the ends and sides scan be squared on the table saw. If it is too big to fit the ends can be trimmed with a router. Use a straightedge along with a jigsaw or circular saw to trim the ends square to the sides. Then use the router to achieve the final edge. Be sure to use a scrap piece of material to support the end of the router run, as you will tear out the end grain if you do not.
When all is square it is time for some power sanding with belt sander followed by and orbital sander in progressive finer grits to cerate a smooth final surface.