Despite the recent silence on the blog, I have been very busy in the workshop building projects for two forthcoming articles for Furniture & Cabinetmaking. In the meantime, the following post is a based on my article from issue 230 of Furniture & Cabinetmaking, and a follow up to the Parallel Skills article I wrote in issue 227.
All crafts have specific ways in which to carry out certain tasks, based on tradition and the tools and techniques commonly available, and in issue 227 I discussed the benefits of looking outside our usual projects to take advantage of the problem solving and techniques found in other disciplines. As a luthier by training who has now embarked on learning the joiner’s craft, I mentioned a couple of lutherie techniques which can be equally useful for furniture building. Since the article was published, several people asked about the lutherie techniques I touched upon. Here I’ll explain why what may seem like specialist techniques for a nice craft have wider applications.
Go Bars – reaching the spots other clamps can’t
Go bars are the luthier’s secret weapon, and provide a versatile clamping system when precise pressure is needed. Essentially, strips of strong and flexible wood are bent into a space too small for them, so that the pressure is transferred into the components being clamped. The most obvious use of go bars in the luthier’s workshop is gluing internal braces to acoustic guitar soundboards and backs, as the clamping force needs to be applied along the full length of a brace while the work piece is held in a cradle matching the radius of the braces.
Go bars can be used for a great number of tasks, and furniture makers can also take advantage of the ability to provide clamping pressure to areas where traditional clamps will not reach. For example, when gluing runners or other internal fittings to a carcase, using go bars will allow you to glue up without the use of either clamps, nails or screws (thanks to Derek Jones for this tip).
Equally, when planing the outside of a carcase flat, the weight of a plane can cause deflection, preventing the plane from reaching the middle part of the panel. Placing several go bars inside the carcase will support the panel and make flattening and smoothing external faces significantly easier.
If you want to make use of go bars for more traditional clamping tasks, then you will need a go bar deck. This can be as simple as you like, and is in essence a base and a ceiling between which the over-long go bars are fitted. The workshop where I trained built the go bar deck so that the bars pressed against the shop ceiling. In contrast, my current deck is portable, with an adjustable ceiling made of four layers of 25mm thick plywood glued together and supported above a deck of the same quantity of plywood by locking nuts on 20mm diameter steel rod at each corner. The work piece is placed on the deck, the ceiling adjusted to the correct height, and bars of oak bent at the points where clamping force is required. The go bars I use are generally made of oak or ash, 20mm wide and 3mm thick, but other species of hardwood will suffice.
Jointing thin panels
Jointing edges for glue up is a familiar task for all woodworkers. Plane both edges flat and square, apply glue and clamp up. Easy. And for work of the typical thicknesses encountered in most furniture builds this is all it takes. But if you need to joint very thin boards, of say, 5mm (the typical starting thickness of timber for an acoustic guitar soundboard) then the work is likely to spring out of the clamps as you apply pressure. Similarly, the thin reference surface makes balancing the plane in a constant orientation to the edge tricky.
Many people seem to view long grain shooting boards as training wheels for novice woodworkers, but for jointing thin stock the long grain shooting board is invaluable as it holds the thin edge in a constant orientation to the plane.
With the edges jointed, we come to one of the key jigs in my workshop; the soundboard gluing jig. An article on how to build one of these jigs will be coming in a future issue, but put simply this is a deck of 25mm thick plywood with hardwood beams on two sides. One beam is fixed at the edge of the deck, while the other is held with bolts which move along slots routed through the deck. The jointed work is placed on the deck and butted up against the moveable beam, and close to (but not touching) the fixed beam. Once the joint has been glued, clamping force is applied by inserting hardwood wedges in the gap between the fixed beam and the work, through the slotted deck. Each half of the work is then clamped to the deck to prevent it springing out.
Because the wedges slide through the slotted deck until they catch on the work, the outside edges of the work piece do not need to be parallel to the gluing surface, or even straight. This jig therefore allows irregular shaped timber to be glued without issue, as well as wedge shaped work where thin outside edges are presented to the clamps.
Sharing information, growing parallel skills
The more traditional joinery I do the more I discover techniques which improve my lutherie, and I hope that the lutherie techniques discussed in this article will prove to find use in joinery and furniture making. If any readers have other techniques which would be of use in different disciplines, please do let me know – let’s share our knowledge and grow each other’s parallel skills.