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5 String Banjo Information:
Assorted 5 String Banjo Construction Tips
**************** MAKE YOUR OWN RAW BRASS BRACKET SHOES ****************
Click HERE for a guide to fabricating raw brass banjo brackets in PDF format.
**************** BANJO NECK LAYOUT GUIDE ****************
Click HERE for a Banjo neck and fret board layout guide in PDF format.
**************** FRET POSITION CALCULATOR ****************
Click HERE for a Excel spreadsheet for calculating fret positions for any scale length and up to 24 frets.
Double click cell B1, type in the desired scale, hit enter, and print out the resulting chart. There is a full decimal equivalence chart so the decimal values indicated can be easily converted to common fractions if desired.
**************** FRET LAYOUT GUIDE ****************
Click HERE for the left side AND HERE for the right side of two PDF files that are designed to be printed and physically joined to make a unique full sized template for accurate layout of fret and position marker locations when constructing banjos and other musical instruments.
Several scales are represented to choose from. The unique properties of the PDF files allow these patterns to print accurate representations of the scale positions. Save the files to your local hard drive and they can be printed out whenever the need arises. When printing the 2 files make certain that the "no print scaling" is selected in the print dialog box and verify by measurement that the borders have been printed to be 7" by 9-3/4". This will ensure that the layout patterns are sized correctly.Carefully trim the left border of the RIGHT layout guide, match it to the right side BORDER of the LEFT layout guide and tape them together. Fold lengthwise at the top of the desired scale and transfer the locations directly to your fret board blank. The 24 frets shown are more than are needed for banjo use, but the guide can also be used for other types of fretted instruments.
**************** BLOCK RIM CONSTRUCTION ****************
Rim layers can be formed easily using the method shown. I cut them with a miter saw, but they can be cut by any other means. I cut 8 segments with 22-1/2 degree angles, leaving the last segment with extra length. Seven segments are glued using slightly stretched painter's tape to hold them tightly together until dry. Cut the last segment for a perfect fit, hold it in place and mark the inner excess material. Cut away the excess material on the inside of the ring before gluing the final segment in place. This saves a LOT of time when sanding the rim to size. Glue the last segment in place and plane level when dry. I use the Wagner Safe-T-Planer in my drill press, but use whatever method you choose. Cut the outer profile oversize before gluing the layer in place.
11" and 12" block style rim patterns:
11" block style 16 segment rim pattern:
**************** RIM CONSTRUCTION WITHOUT USING A LATHE ****************
Here's an alternative to lathe forming a rim. The pictures should be more or less self-explanatory. The secret is to form a base with a precisely sanded outer diameter. The circular base rides against two guide boards located to the right and to the rear of the base and clamped securely to the drill press table. Slightly oversized segments are glued directly to the base and accurately sanded with an 80 grit drum sander. Adjust the right guide board to control "depth-of-cut". You should take multiple light passes until the desired dimension is reached. Use medium speed and keep your work moving to avoid burning the wood. Cut or plane away the base to reach the inner portion that could not be initially shaped with the sanding drum. Clean up the outside and inside surface with a random orbit palm sander fitted with a 220 grit disk. With a little care you can easily produce a rim that rivals its lathe-turned counterpart. The photos below show how this is done.Rim construction sequence is as follows:
1. Glue first (bottom layer) to a circular pattern formed from void-free plywood to serve as a sanding guide. I always use a few grains of salt on the glue surface to keep layers from sliding when clamping pressure is applied. If your layers are level they can be clamped with pressure exerted from a central point above the rim.
2. Sand outer diameter of first layer to match circular sanding guide. The inside diameter of this layer is sanded as the last step.
3. Glue second layer in place.
4. Sand outside diameter of second layer to match first layer.
5. Sand the second layer inside edge to the appropriate diameter and outside diameter to match the second layer.
6. Glue the third layer in place.
7. Sand the third layer inside and outside diameter to match the second layer.
8. Glue the top layer in place.
9. Sand the top layer inside and outside diameter to match the third layer.
10. Remove the circular sanding guide. Excess material can be removed from center and the remaining material can be planed away.
**************** ANOTHER BLOCK RIM CONSTRUCTION IDEA ****************
Here’s a quick picture to demonstrate another idea for an easy alternative to lathe use when making a rim. Any size rim with any wall thickness can be created this way. Each segment is precut to the desired OD and ID plus a little extra for sanding purposes. The first segment’s ends are sanded and it is glued to a plywood disk whose outer edge has been sanded to the desired finished O.D. Each additional segment has both ends sanded prior to adding it to the rim. The mating end is additionally sanded to form a more or less perfect joint when it is added to the previous segment. The salt shaker is used to sprinkle a few grains on the glue surface to prevent the segment from shifting out of place when clamp pressure is applied. If a small disk sander is used, the joints can be mated to create an almost invisible glue line. When all the layers are complete the plywood form can be cut or planed to remove it or it can be used as a reference to sand the rim using a 2” sanding drum mounted in a drill press as shown above.
**************** DRILLING RIM HOLES ****************
Drilling the rim for bracket holes can be done using this simple drill press fixture. An extension arm is clamped to the side of the drill press table to permit the holes to be drilled perfectly perpendicular to the rim face. The top of the overhanging arm is rounded to match the inner diameter of the rim to prevent tear out when the drill bit breaks through the inner face of the rim.
The second method shown in the photo below utilises a hand drill. A guide block with rear face curved to match the rim outside diameter is fastened to the bench top. Alignment marks are drawn on the rim face and the top of the guide block to accurately locate the rim hole positions. The rim is clamped in place against it using a curved sacrificial guide against the inner rim surface. The bracket hole can then be drilled using the guide hole with no tear out on the rim surfaces.
**************** ADDING A NECK REENFORCEMENT BAR ****************
I commonly use an 18” length of 1/4” thick 2024-T4 aircraft aluminum bar stock that tapers from 3/8” at the nut end to 5/8” at the heel end of the neck in my banjos, but it is not necessary in a well-built nylon strung banjo. Do not use ordinary aluminum bar. If you can flex the bar by hand it is not stiff enough to be effective in preventing neck bow. The bar can be cut easily on the band saw, but avoid overheating the bar when cutting it. The top and bottom edges of the bar must be sanded smooth and flat. The bar is installed by routing a 1/4" wide channel that is cut 1/2" deep at the nut end and tapers to 3/4" deep at the heel end. The channel is routed using several progressively deeper passes until the desired depth is reached. The bar is glued into the channel with a filler strip clamped over its top. The filler strip is finished off to be level with the top surface of the neck after the glue has dried. An example of this type of bar is shown in the photo.
The details for making and installing this type of reenforcement bar can be found HERE at my other website.
**************** FRET BOARD LAYOUT ****************
Here's a quick animation demonstrating the steps used in banjo fret board layout. It takes a little over a minute to cycle through the steps. Use of your browser "refresh" button will restart the animation from step #1. The "stop" button will freeze the animation at its current frame until the "refresh" button is used. The captions used are listed below with additional explanatory text added.
1. Banjo fret board layout on a typical 20” by 2-1/8” fret board blank.
2. Draw horizontal center line on fret board blank. All measurement is done from this line.
3. Draw third string path below center line by dropping the nut end of line 3/16” down from center line. All vertical lines will be drawn perpendicular to this line. This is done so the nut and frets will be perpendicular to the pot center line when the neck and pot are joined. The neck will be "rotated" slightly around the center point of the heel causing the third string path to be exactly on the extended pot centerline. This is done so the strings will center over the neck heel when the instrument is assembled. The third string should be a perfectly straight line from the nut slot, over the heel center, and extending to the center of the tailpiece.
4. Draw nut and heel locations. Be sure to draw all vertical lines perpendicular to the 3rd string line drawn earlier. Note that the heel location is independent of the actual scale length and determines where the bridge will be placed on the head. Heel position is calculated by subtracting the heel to bridge distance (pot diameter X .6) from the actual scale length. The resultant dimension is the nut to heel distance. This is the actual length of the finished fret board.
5. Draw 4th and 5th fret locations.
6. Mark the centered nut width. The example shown is 1-3/8”, a typical clawhammer style banjo nut width.
7. Mark centered heel width. The example shown is 2”.
8. Connect marks on first string side.
9. Draw a line from nut to fourth fret on a line between the marks on the fifth string side.
10. Add 5/16” to the distance from the center line to this line at the 5th fret and mark the new width. This additional width varies based on personal builder preferences, many builders add 1/4" for the fifth fret bump out distance.
11. Draw a line between the indicated 5th fret width and the mark at the heel.
12. Draw the curve connecting the lines between the 4th and 5th frets.
13. Draw the remaining fret positions on the blank. Seventeen are shown. This is a popular number for many clawhammer players, others like additional frets.
14. Draw a line parallel to the 3rd string path line on the 1st string side. The blank can be trimmed to this line and the edge used for a reference for cutting the fret slots. It is generally easier to cut fret slots with a little extra board width. This minimizes the possibility of chipped slots when the saw exits the cut. Some prefer a minimum of width if cutting frets by hand (shudder...) as it reduces overall blade friction while cutting.
**************** FRET BOARD SLOTS ****************
An example of how to cut fret slots is shown below. This small tile saw has been retrofitted with a jeweler's slotting blade that cuts a precise .023" slot width for standard frets. If you make a lot of instruments that require frets this saw works beautifully.If you are making a fretless neck it does not need this kind of precision, and any type of saw can be used to make the slots which are filled with a contrasting wood strip. Sand the strips to match the slots, glue them in place, and sand them level with the fingerboard surface.
**************** SHAPING THE NECK ****************
Cut the neck profile out to match the shape shown on the plan. Try and cut the profile as closely as you can to reduce sanding time. Use extra care when cutting the flat area at the rear of the peghead and the thumb stop profile. This will make it easier to easily transition from the rounded portion of the neck when it is shaped with the sanding drum.The neck profiles (cross sections at several fret locations) along the neck are available on the print. Place a flexible sheet of plastic over the guide and trace over the pattern with a fine tip permanent marker. Cut out the areas representing the neck profiles.
One of the easiest ways to shape the neck is to round out the desired shape at the several fret locations using the guide, remove the waste areas between the shaped locations, and finish by refining the areas to eliminate irregularities. Round the heel area and blend the neck into the heel in a continuous smooth transition. A smaller drum sander (3/4” course grit) can be used to profile the thumb stop area. You may wish to practice your first attempt on a scrap piece of lumber. If you error beyond saving, pitch it and start over. After all, it’s just a piece of wood.
The picture shows the first two template locations at fret positions 1 and 3 rounded with the 80 grit sanding drum. The rest of the locations will be rounded in the same manner prior to removing the waste areas between the locations.
**************** BANJO NECK GEOMETRY ****************
The unusual geometry that develops as a result of the asymmetrical neck and short fifth string of the current five string banjo design necessitates a little tweaking to enable the strings to be centered on the neck. It wouldn’t be much of an issue, except the five strings create a natural center line that invites visual scrutiny. Modification of the neck angle is also necessary to center the strings over the asymmetric fret board. In order to create a balanced appearance and assure the centering of the strings over the fret board the following steps are suggested.
Fret slots:
When the fret board is made the fret slots and nut end should be cut to be perpendicular with the third string path. (This path will coincide with the true centerline of the pot if the neck is attached correctly, as outlined below.)
Fret board position marker location:
The position markers should be centered on a line that runs from the center of the neck heel to a point half way between the center of the nut and the third string nut slot. This may require a little thought to visualize, but it is a way to reconcile the apparent visual centerline (the third string path) and the actual center of the fret board. The positions are shifted to “split the difference” between these two lines.
Adding the fret board to the neck blank:
This one is easy. The midpoints of the nut and heel ends of the fret board are positioned on the neck blank centerline so the board and neck laminations will appear as being centered and symmetrical.
Mounting the neck to the pot:
With the heel center positioned on the pot centerline, the entire neck is “rotated” slightly clockwise (when viewed from the front) to place the third string nut slot directly over the pot centerline. This is accomplished by slightly canting the heel profile when it is formed. Note that this "canting" of the heel profile works in conjunction with the neck heel angle as outlined below.
**************** NECK HEEL ANGLE ****************
One of the problematic areas for new builders is the question of proper heel angle cut. Three degrees is often the suggested angle, but in reality the answer is more complex than that. A small change in heel angle will result in a substantial difference in the bridge height necessary to achieve proper string clearance over the frets at the upper end of the neck. Although there are mathematical relationships that can be used to calculate the theoretical ideal heel cut angle, in actuality it’s difficult to accurately reproduce this ideal calculated angle in the average home shop.
Skip the following paragraph unless you like headaches...
“Can I use a simple math to calculate the heel angle?” Yes and no. You can use trigonometry to ascertain what the desired heel angle needs to be. The first thing you need is a right triangle with the long side equal to the distance from the neck heel to the bridge. The short side of the triangle is the "rise" which is the bridge height minus the distance between the head and strings at the neck heel. In our diagram above we need to subtract the distance from the head to the strings at the edge of rim from the height of the bridge to come up with the needed triangle shape. Draw a line parallel with the head which intersects this point and extends to the bridge to envision the triangle shape. Got it? Even this simple angle isn’t perfect because the strings and the surface of the frets are not parallel due to the increased height of the strings over the upper frets, but its close. OK, we’ve got our right triangle with the two needed dimensions of distance and rise. For simplicity’s sake we’ll say 6” and 1/4” are distance to bridge and the rise to the top of the bridge. Opposite side (.25) divided by adjacent side (6) gives us a tangent of .0416666. Checking the tangent tables we find that .0416666 lies somewhere between 2 and 3 degrees. We guessed that much. Luckily the tangent tables are more or less linear, so we can use simple ratio in proportion to calculate the exact angle. We’ll use the tangent for 2 degrees (.03492) as one portion of our ratio. Doing the math, we get (2).0416666/.03492=2.386403 degrees. Good luck with setting that angle gauge to 2.386403 degrees! Let's move on to a real world method of calculating and cutting the heel angle.
My neck design preference utilizes a 3/16” thick fret board incorporating a 1/8” scoop set flush with the head surface. My heel angle is cut so a straight edge placed across the top of the frets intersects with the bridge position 3/8” above the head surface as illustrated in the diagram. This results in a nearly perfect action when a 5/8” bridge is used. Any further small adjustment in string height above the upper register frets is taken care of by raising or lowering the heel position on the rim.
I’ve found that for me the best way to achieve the angle necessary to produce this desired measurement is to make a preliminary cut, mate the heel to the rim and check the result by placing a straight edge across the top of the frets and checking the resultant distance above the head where the line intersects with the bridge position as illustrated in the diagram. The angle is adjusted slightly if necessary to achieve the desired 3/8” measurement.
Every banjo design presents a unique combination of variables that affect the ideal heel angle. Head deflection is one of the variables that must be considered. Factors effecting head deflection are head material, diameter, tensioning, bridge height, down force from string angle from bridge, additional down force from an adjustable tail piece if used, neck angle, string material, string gauges, and tuning. You can generally figure that the bottom of the bridge will end up 1/16” to 3/16” lower than the top plane of the head after the string tension is applied to the bridge.
Another factor that plays a key role in determining the heel cut angle is the design of the fret board and how it intersects with the level of the head. Non-scooped fret boards, necks positioned higher or lower than the plane of the head, or bridge height more or less than 5/8” will obviously require a slightly different heel cut angle. It helps to make a full size drawing of your neck and pot prior to cutting the heel angle to visualize these relationships and get a good idea of the initial heel cut angle.
Don’t forget that the neck also needs to be slightly “rotated” so the third string path will line up on the pot centerline. (See the entry under BANJO NECK GEOMETRY to get that portion of the total picture.) This means that the heel cut must result in a neck that both angles back and is skewed slightly clockwise when viewed from the front of the instrument. I suspect that most small scale builders develop a heel profiling system that works for them and then rely on that methodology to achieve repeatable results for their instruments. My heel profiling system is based on a vertical oscillating spindle sander as shown elsewhere on this page, but many other builders use many creative solutions to achieve the desired results.
**************** FORMING THE HEEL PROFILE ****************
Shown below are two of the many ways to form the heel profile. The first picture shows a jig that uses an oscillating spindle sander and easily creates a heel to rim fit that I used to only dream about! Any arrangement that presents the heel to the sanding drum at the correct radius and angle can be used, as shown in the second photo of a drill press based fixture.
**************** FITTING PEGS TO THE PEG HEAD ****************
The method shown can be used to install any tuner of any type without damage to front veneer overlay or the rear surface. Drill a small dimple where the tuner will go, hold the guide and bit tip against the dimple, and clamp the wooden drill bit guide and backing board in place. Pull the bit out and check centering by looking down the hole with a small flashlight to ensure proper centering before actually drilling the hole. This particular hole is 9/32" for the violin tuners used on this banjo. A tapered reamer is next used to enlarge the holes to match the pegs exactly.
**************** ATTACHING STRINGS ****************
How to attach strings so they don't slip when tightened. The diagram should be more or less self-explanatory.
**************** NUT VISE ****************
Here is a simple vise that can be used to hold the nut while cutting and shaping slots. It uses a short piece of "fret board" at the front to simulate an actual fret board. A simple eccentric cam at the back locks the nut in place while it is being worked on.If you are using frets, a pencil which has been sanded so only half remains can be used to mark a line on the front face of the nut to use as a reference in determining how deep to cut the initial slots. Stay slightly above this line when preliminarily shaping the slots and do the final fitting on the instrument when the strings are added.
The nut slots are cut to be just above the level of the fingerboard (the thickness of a business card serves as a convenient guide) if you are building a fretless instrument.
**************** MAKE YOUR OWN BANJO TENSION GAUGE ****************
Click HERE for the complete directions for constructing your own banjo head tension gauge using an inexpensive import dial indicator as shown below.
**************** A QUICK VISIT TO THE SHOP ****************
A quick visit to the homestead and shop can be found HERE.**************** OPEN BACK BANJO CONSTRUCTION GUIDE ON CD ****************
Information on the purchase of my Guide to Open Back Banjo Construction on CD with full size printed plan can be found HERE.
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Please visit my other website designed to provide information on musical instrument construction. There are free plans as well as construction tips and techniques available at the present time.
Rudy's Sketchbook of Musical Instrument Plans, Ideas, and Inspiration
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