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Making Trussrods

Making a one-way twin-rod system

Making your own one-way twin-rod system is not particularly difficult. Take a 5mm (3/16")-diameter steel rod of twice the length of the truss rod channel plus about 50mm (2") as a reserve, mark it in the middle and, using a triangular file, make a 2mm (1/16")-deep groove at this mark. Then heat this point over a propane torch (1), turning the rod over the flame until the heated area is red-hot. From now on you have to be very quick because the rod must not cool down. Before starting to heat the rod you should fasten a piece of the rod or a nail vertically in a vise. Now bend the rod around the piece in the vise, with the filed groove on the inside as shown in picture 2. Press the ends of the rod together and use a hammer to flatten the area where the rod has been bent (3). If you are no stranger to welding you could get the same result by welding together the ends of two separate rods over a length of about 13mm (1/2"). After that file the weld flat so that the rod will fit into the truss rod channel nicely.

Shortening the rod is best done by placing it inside the channel and marking a point on it 10mm up from the cross channel towards the end of the neck. Mark and cut off the second end exactly in the middle of the cross channel. Finally, smooth and deburr the end areas and all edges.

The thread is cut onto the longer of the two bars (4). It should be made about 25mm (1")-long, using a 5mm die for a 5mm rod and a 10-32 die for a 3/16" rod. Fasten the rod in a vise, put a wedge between the two bars to get the shorter end out of the way, place the die on the longer end and turn it clockwise, exerting only little pressure. It takes a short while until the die really starts to cut. Each time two or three turns have been made turn the die back counterclockwise by about one turn and add a drop of oil. When turning back the die you will hear a noise - that of the iron filings breaking.

The bearing cap for the twin rod is14mm (9/16")-long; cut it from a 20mm (3/4")-wide and 5mm (3/16")-thick flat metal bar (5). Mark the center of the top hole 3mm (1/8") and the center of the second hole 9mm (11/32") from the top edge (6). Centerpunch the hole centers accurately and drill the lower hole all the way through the cap, using a 5.5mm (13/64") twist drill, and the top one, only 3mm (1/8") deep, with a 5mm (3/16") bit (6). To do this use the drill press and its vise.

The adjustment nut should be made of brass, which, because it is softer than iron, cannot damage the iron thread of the rod.

When the neck is finished, access to the truss rod is no longer possible. I was not able to get hold of a 20mm (3/4")-long 5mm thread brass nut with allen head and I am not sure whether you will, so you might have to make one yourself (7,9). For this you could, for example, take a 10mm-diameter brass rod, cut a 25mm-long piece off it and drill a hole into its center, using a 4.2mm drill bit for a 5mm thread (if you use a 3/16" rod use the appropriate drill bit and thread cutter). If you have access to a lathe, this will be an easy job and quickly done. Alternatively, you will have to center-punch the piece and clamp it exactly vertically in the vise of a drill press. The vise should have a V-groove in the middle of its jaws. Next cut a 5mm thread into the hole just drilled. Use a 5mm allen bolt which is threaded all the way up to the head as an allen head and shorten the thread to a length of 5mm with a hack saw. If the thread should not go right up to the head of the screw - the thread often ends 1mm to 2mm under the head - you will have to enlarge the beginning of the brass nut thread with a 5mm drill bit. Apply a bit of super glue on the thread and turn the screw into the brass part. Next mark and drill a 2mm-diameter hole on the side of the brass part, 3mm from the edge. This hole should go exactly through the screw but not all the way through the brass part. Put some glue around the hole, hammer in a steel pin - sawn off a 2mm-diameter steel nail, for instance - and there you have it, your very own brass adjustment nut with allen head. It would, of course, also be possible to use a nut with a slot for a screwdriver. It would also be conceivable to use a long hex nut as long as you make sure that you can still get at it with a wrench.

Before you install the truss rod put the bearin cap on it and wrap gummed metal tape or strong fabric tape tightly around the whole length of the rod (8). Place the layers next to each other and try to avoid too much overlapping as the rod must not become too thick. Press the rod to the bottom of the channel with a screwdriver; a snug fit is desirable, but don't make it sit in there too tight. A truss rod fitted too loosely can cause unwanted noises later. If the rod should have been made too thick to fit into the channel, make the channel wider with a router. Do so very carefully, making sure that the cutter is exactly in the middle of the channel. Put a strip of adhesive tape on the edge guide of the router and cut along one side of the channel.

Picture 9 shows a one-way twin-rod before installation. The cross channel for the truss rod bearing cup and the adjustment nut cavity at the end of the neck can also be seen. Make sure that the longer of the two iron rods - the one which has the thread - is installed at the bottom of the channel, facing the back of the neck. A wooden fillet will be glued over the truss rod. The channel itself is 13mm (1/2") deep. The access opening to such a type of truss rod should always be on the body side of the neck.

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Use 5.5mm (13/64”) drill; drill thr u

Steel pin

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