Musical instruments make for a unique woodworking project in many ways, not the least of which is the amount of tension they must be built to withstand. Guitars, for example, have over a hundred pounds of string tension on the neck and bridge, while harps can have over 1000 pounds of string tension All of this tension means successful glue joints in musical instruments are critical!
In order to achieve a good glue joint it is important that the wood parts be held together FIRMLY while the glue dries. Clamps are the most common means of achieving this task. Here at Musicmakers we have a wide variety of clamps available for just about any purpose, but many kit builders don’t have a shop full of expensive clamps. The good news is that, in many cases, you can get by without clamps and use some hacks or tricks for clamping without clamps.
Let gravity do the work! Maybe you have a weight set sitting in the basement, or some unused cinder blocks. Maybe you like to buy in bulk and have a 40 lb. bag of rice in your pantry..We have an old train rail section in the shop we use for clamping almost daily. Sometimes it can be tricky to balance the weights on the objects you are trying to bond. It can be helpful to tape wood pieces together to prevent them from sliding out of place once you apply the weight.
Cams are a circle with a pivot point that is slightly off center. Basically, while turning the cam, the outer diameter of the cam will come closer to the part being glued and apply pressure. You can make several cams and screw them to a plywood board or bench. Use the screw in the cams as the pivot point. I like to make a handle extending from the cam. Adding pins to hold the cam in place is quite helpful and prevents them from popping back under pressure.
3. Elastic Ropes
Anything rope-like with elasticity works great for clamping: surgical tube, bungee cords, rubber bands, and yes, even those elastic workout bands. There are a couple of ways to use elastic bands. If you’re wrapping around something you can do one wrap and tuck the rope under itself or tie the elastic rope to itself in order to anchor the the rope. Continue to wrap the band as many times as needed and anchor the rope in the same manner at the end so it doesn’t come undone while waiting for the glue to dry.
The other method is what I call the Gulliver’s Travels approach (like the giant that gets tied to the ground with rope). Partially screw a bunch of screws to a piece of plywood or workbench around the perimeter of the parts being glued. Use the screws as anchors for the elastic ropes to wrap around. When using the elastic rope method, make sure to constantly apply tension to the rope. We sell 20 foot lengths of bungee cord on our website.
This is my favorite way to clamp. A go-bar-deck uses bent sticks to apply pressure. The underside of benches, shelves, ceilings, or even the instrument itself (common in piano repair) can work as a go-bar-deck. Be aware that as much pressure is applied up as is applied down, so make sure you’re using something secure for the top of the deck. Cheap dowels at the hardware store can be used as sticks, or you can make your own sticks. The stick only needs to be bendable and slightly longer than the distance between the parts being bonded and the ceiling of the deck.
Using wedges as clamps is one of the first tricks I learned in luthier school. Screw two parallel fences (can be scrap wood) to a piece of plywood or a workbench. Place the parts you’re bonding between the two fences with some extra open space. In the open space tap pairs of wedges into each other with a hammer along the length of the parts (it usually takes 3-4 pairs of wedges). Sometimes you may need to put a weight on top of the parts being glued so they don’t pop up. Warning: don’t glue your parts to the bench.
We use tape in the shop all the time for bonding parts. It’s important that the tape have some elasticity to it. Stretch the tape and hold the stretch while applying the tape. This gives the tape more force for bonding the parts. Masking tape will do on lighter jobs. Double up a couple pieces of masking tape together to give the tape more strength. Go for strapping or filament tape if you need to apply a bit more force. I hope you find some of these tricks helpful.
Jacob Nelson, Luthier