How to Joint Veneers
Thursday 10 December 2009
I struggled with veneer jointing when I started out - nothing looks worse than a black line on a joint in sycamore. So how do you get that elusive seamless join?
Preparation is the key. You must, of course, start with absolutely flat veneer, but the edge is what we are considering here. In my experience this edge cannot be achieved by cutting against a straightedge with either a veneer saw or a scalpel because simply changing the angle on the tool will not provide a true straight, square edge.
Shooting by hand
Most makers will shoot a single leaf or pack of veneers with a long hand plane rested on its side. This technique will get good results and the longer the plane - a No. 8 is my favourite - the better the results will be. It is not without its disadvantages, however, the first being that some sort of shooting board will need to be fabricated.
Mine is made from ply and is hollow to allow clamps access to the centre of the veneer. A piece of MDF is used to pack down the veneer and ensure a good straight joint. This technique can be difficult because the veneer that is exposed can bend over as it is being planed and then spring back after the plane has passed.
This led me to think of a way of improving veneer shooting, so I started looking at methods involving machines.
Using router or spindle moulder
A bearing-guided router cutter or spindle moulder will produce perpendicular cuts that are flush with the template. Using this information we can clamp our veneer between two layers of MDF and run our bearing against one of them. This can be done with a hand-held router, router table or spindle moulder, machine choice being down to the size of the veneer leaves.
I can use the hollow shooting board I mentioned earlier with my hand-held router. This technique is very quick and I use it all the time. In fact I cannot remember the last time I hand-shot veneer.
I will hand plane or surface plane the MDF that will be used as the template for the bearing to run against and this technique can be used to trim veneer for all sorts of patterns.
Even small pieces of veneer can be trimmed to a template. Tape the veneer between two pieces of MDF. If the veneer is small and you need to trim all the sides, just rout through the tape on each side and replace it before going on to the next side. This is great for starburst effects and the template can even be CNC machined for increased accuracy.
Using surface planer
Another way of machining veneer joints is on your surface planer.
As with the other techniques, secure the veneer in F-clamps between two pieces of MDF slightly longer than the veneer, pointing the clamp handles towards you as these become your handles when planing.
For the sake of safety, before attempting this bring the fence forward right over the bed, leaving only just enough room to position the jig over the blade. While a small section of the blade is exposed and cannot be guarded, your hands are firmly on the F-clamp handles and nowhere near the rotating cutter.
Only relatively short lengths of veneer can be catered for with this technique.
Once you have your veneer cut and trimmed then the final job of actually joining these together needs tackling. I have tried gum tape and veneer tape and I am not a fan of either - introducing water anywhere near the veneer either before or after joining the veneer seems risky because you do not want veneer expanding or contracting.
I have tested many tapes and have found genuine Sellotape to be the best for me as I vacuum press all my veneering. It does not leave a sticky residue and is easy to remove as long as you fold over a corner before attaching it to the veneer. Take care, however, when removing the tape as it can pick out some of the grain.
If you need to join many sections together or it is a complicated piece of veneering, the material can be glued together and treated as one large sheet. This technique is also particularly useful when using heated presses as the tape will melt on the veneer, making it very difficult to remove. It may also leave an impression where the tape was.
When taping the veneer together, space the Sellotape strips about 25mm apart and stretch it across the join. When the whole join is taped run a continuous stretch along the length.
If you want to glue the join do this now by first folding down the two leaves, then applying the glue with a small brush or roller. Fold back the leaves and put a weight over the join until the glue dries.
Remove the tape carefully to reveal a large sheet of veneer. Whether you glue the join or not, the veneer sheet can now be pressed on the substrate.