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Web guide to constructing a basic 5-string Banjo.

This page...Introduction and Rim construction.

Click on any image for a larger view.

Basic 5-string Banjo as completed from this guide.

This guide serves to illustrate the construction of a basic 5-string banjo. It is of simple design using guitar-style tuners and a unique head-tensioning mechanism. It is assumed the builder has access to a drill press and band saw, although other techniques could be utilized in it's construction.
...Heck, you could probably just about build a banjo with a pocket knife if you had to...

Criteria used in the design of this instrument were:

Later upgrading or modifications were taken into consideration when the basic design was drawn. This included conversion of the head tensioning system to utilize the tone ring/head/tension hoop/brackets-hooks-nuts combination found on most open-back banjos and modification of the peghead to accomodate the more traditional (and expensive) vertical tuning pegs as found on most banjos.

Having said that, I will say that after completing this banjo, I won't change this one at all. I like it's spartan look, and the sound is quite nice...well-rounded, not harsh, but is not as loud as some open-backs I've heard. But then, it's not a tubaphone, either.

There's a place in the world for banjos of all types and this one meets all of the above criteria and also sounds great in the process.

This is page 1...Rim construction, glue-up and forming basic rim.
Go to Page 2...preliminary mounting of the head.
Go to Page 3...Making the neck.
Go to Page 4...Making the neck, continued.
Go to Page 5...Installing frets.
Go to Page 6...Bringing it all together.
Go to Page 7...Outer rim band and miscellaneous details.
Go to Page 8...Finishing and final assembly.
Go to Page 9...Basic banjo drawings and notes.
RETURN TO HOME PAGE

"Now, a word from our sponser..." (a word or two about hardware)

At top is a section of the "Aircraft Aluminum" used for neck reinforcement. It is available at your local steel supply house. I paid about 25 dollars for 12 feet of this, but that builds a lot of necks! Some machine shops may also have small quantities of this. The vitally important thing to ask for is the 2024-T4 material designation. Do not use hardware store variety aluminum bar. If you can bend the bar by hand, it is not strong enough.

Below it is #10X24 by 1-1/4" stainless steel square drive bolts, stainless steel nylon insert locking nuts, #10 by 1/2" and 1" allen head set screws, tee nuts, #10 stainless steel flat washers, 3/32" long arm allen wrench to adjust head tension and tighten dowel rod bracket, and garden-variety slot-head guitar tuner example.

See the Suppliers/materials recommendations at the bottom of the drawings and notes page.

Consumable rim form

The pot is formed by gluing layers directly to a consumable form as shown here. The radial lines represent the actual spacing of hooks on a standard 24 notch tension band. This banjo uses this spacing so the holes used to fasten the mylar head in place can also be used to mount brackets for hardware to convert to a standard tensioning system should it be desired to do so in the future.

The two outer circles, 11-1/4" and 9-1/4" diameter, show the area to which pie-shaped segments will be glued to. Sand the form to the outer line, working CAREFULLY to the line. The finished rim uses this line as a guide when the rim is trued, so the finished rim will only be as uniform as the pattern. The rim will be formed of 1" wide segments later sanded to 3/4" finished dimension.

The 1/4" holes in the pattern are the locations where the tee nuts will be installed in the finished rim. They are used as drilling guides by turning the form over and drilling through the segments as each successive layer is added to the rim assembly. Lay them out at the locations shown on the plan on a 10-1/2" O.D. circle drawn on the pattern.

Segment pattern

Draw an arc slightly greater that 90 degrees at 4-5/8" and 5-5/8" radius to use as a pattern.

Waste not, want not

Draw 12 segments on a maple board planed to a uniform thickness of 13/16" and cut out the segments. If desired, 3/4" can be used.

First layer after gluing and drilling through guide holes in form

Four pie-shaped segments were cut for each layer of the rim assembly. They are cut to match the guide line drawn on the form at 9-1/4" I.D. and the outer edge of the pattern. This allows 1/8" excess wood on inside and outside of glued-up rim blank for sanding. The ends of the first section were sanded smooth on a disk sander and it was glued in place. Lay out the segments to miss areas where the neck, tailpiece, and head mounting or tensioning screws are located. Butt each successive segment to the previous segment, adjusting the angle until a perfect fit is achieved. The forth and final segment is carefully sanded on both ends to match the first and third segment ends before gluing in place. If the resulting layer is not reasonably flat after glue-up, a light pass under the Safety-planer will prepare it for the next layer.

Invert the rim after each layer is finished drying overnight and drill through the guide holes with a 1/4" brad point bit held in the drill press to assure accuracy.

Completed rim glue-up

The rim was formed from three layers 13/16" in thickness and a final contrasting layer about 3/8" thick. The 3/8" layer was planed by making several light passes under the safety planer to remove the clamp marks and true it to its final 1/4" thickness. Assembly was then inverted and 1/4" holes were drilled through the final 3/4" layer and 1/4" cap layer. Use back-up board under the cap to minimize tear-out.

This shows the completed rim glue-up including rear cap sections.

Truing the outside of the rim

A guide is clamped to the drill press table for the consummable guide disk to ride against. The guide has been reduced in thickness at the points where the guide disk contacts it to eliminate the possibility of the rim contacting the guide. The area below the sanding drum has also been thinned to allow the drum to be lowered enough to sand the full width of the rim. The guide is clamped to the drill press table in a position which will allow the sanding drum to remove a small amount of material from the outer surface.

Sanding is accomplished by holding the rim securely against the guide and rotating it against the drum. Contrary to logical thought, this process is easier when the rim is rotated in the same direction in which the drum is turning. Make certain to maintain a firm grip and exercise all normal safety precautions. A feeling for the technique can be gained after a few short minutes of actually doing it. A carefully positioned shop vac hose will make this a much more enjoyable process. The drum can be lowered to permit sanding of the entire width of the rim. Reposition the guide and continue removing material until the rim reaches it's finished 11" outer diameter plus 1/32" for finish sanding. The pattern will end up protruding over the rim, but will be planed off later.

Truing the inside of the rim

Once the outside of the rim is trued, the guide can be repositioned to allow the inside of the rim to bear against the drum sander. The rim is trued in several light passes to bring the rim wall thickness to 13/16". This will result in a finished wall thickness of 3/4" after sanding is completed. The rim is finished down to the lowest point that can be reached with the consummable guide still intact. It will be necessary to remove the inner portion of the guide disk with a jig saw to permit the sanding drum to reach the full width of the rim.

The rim can now be inverted and the remaining portion of the guide disk planed off in several passes under the Safety-planer.

Forming the tone/tension hoop

Forming the tone/tension hoop is the most complicated operation to be performed.

The base of the bending jig is composed of two 3/4" layers stack-glued and cut/sanded to a uniform 8-5/8" outer diameter. A recess is also cut near the outer edge in order to bolt the end of the aluminum bar to the form. There is a 4" square glued to the bottom to provide a way to clamp it in a vise. A 5/8" diameter hole is drilled in the center to hold the bending arm pivot dowel.

The bending arm is 24" of 2"X2" with two 5/8" sections of dowel rod inserted in holes drilled 6" on center. All of these dimensions are fairly critical to produce a hoop having a 10-3/4" outside diameter.

The aluminum bar is formed from 48" of 1/4" by 1" common aluminum found in the hardware store. It is cut easily along it's length with a band saw to produce a 1/2" wide bar. Sand the cut side smooth and form the opposite "Factory" edge into a radiused edge. I first cut each edge to 45 degrees and then rounded the resulting edge. Drill a 3/16" hole in the end, bolt to the form, and insert the pivot dowel in the center hole. Hold the aluminum straight and roll the hoop around the form in a slow and continuous motion. This is really quite easy. The aluminum will have to be angled down slightly to avoid the bolted end of the aluminum at the overlap point.

Tone/tension hoop after forming

This is the hoop after removing it from the form. Wait until after the rim has had the hoop recess cut before trimming it to length. This will ensure the rim can be cut to achieve a slip fit. This is necessary to allow the rim to be raised by the tension screws to tighten the head.

Cutting tension/tone hoop ledge

The guide is now repositioned to cut the tension/tone hoop ledge in the rim. This is done with a 3/4" router bit which protrudes from the bottom of the table. The depth is set at 1/2" and several light passes are made until the ledge is 3/8" wide. Maintain a firm grip and feed the rim against the rotation of the router to prevent the rim from catching.

The tension hoop is then positioned over the rim and trimmed at the spot which will produce the best fit on the rim. After the hoop is cut, test-fit the hoop over the rim to ensure proper clearance. When the fit is correct, drill 1/8" holes 1/4" deep into each end to house a corresponding length of 1/8" rod. This holds the ends in permanent alignment. After the ends are joined, the top of the hoop can be checked to make certain it is radiused correctly and sanded smooth.

The rim can be touched up on the router table if there is insufficient clearance to allow the hoop to easily slide over the rim.

Installing rim tee nuts

Twelve #10X24 tee nuts are inserted into the twelve rim holes after the flanges are trimmed to fit the rim ledge. The protruding prongs of the tee nuts have also been trimmed away. The barrels of the tee nuts should be a snug fit, requiring a few taps with a wood block to seat them.

Drilling the head mounting holes

The rim is laid out once again using 12 of the same hole locations as the brackets would occupy on a standard 24 bracket rim. Due to the spacing on the standard 24 bracket rim, the first bracket location on either side of the neck is skipped and the holes are layed out and drilled at every other bracket location..This places the head mounting points somewhat farther apart at the neck and closer together at the tailpiece location. This is somewhat of a compromise to enable using the rim later for conversion to the more traditional system of tensioning, should it be desired to do so.

Go to Page 2...preliminary mounting of the head.