Sunday, October 4, 2015

Banjo Boys - Chapter 32 - The Death Saw

Clint and Bob at work on the "death saw"
It's been a very long time since you've heard from the Banjo Boys.  Some of that silence had to do with the fact that it was too hot to work in the shop.  Some had to do with distractions other than banjos.  But this weekend, Clint came up to the shop to build a new jig, inaugurate a "new" tool, and to shape the heel of a banjo neck that goes back several months.

The surface of the banjo neck that attaches to the rim is critical to the proper alignment of the neck.  It must first have a slight concavity when looked at from above to accommodate the convex shape of the rim.  That concave profile must be symmetrical from side to side to ensure that the center line of the neck extends through the center of the rim (you want the bridge to be centered across the rim perpendicular to the axis of the fingerboard).  And there is a precise tilt to the neck that ensures that with the string clearance correctly set over the frets, the bridge height on the banjo head is correct (usually around 3/8").

On our earlier banjos, we had crafted a jig that we used on a table saw.  I wrote about that jig and its operation in Chapter Seven of the Banjo Boys' saga.  It worked, but had a fair amount of variability in the resulting heel surface.  Clint had realized that when Chris Dean built his Dynaflow banjos, he used a radial arm saw to shape the heel contact surface.  It looked to both Clint and me like a much more controllable, repeatable, precise method.  That led us to today's project - build the jig and shape the rim-contacting surface of the neck on Clint's latest banjo using a radial arm saw.

I acquired a non-operative radial arm saw many years ago for around fifty dollars.  It was missing several pieces, including its safety guard that covers the spinning blade.  Using eBay, I gradually had completed the saw but had never had a need to use it.  I'm so used to doing most of my instrument work on the table saw or bandsaw, I simply never thought about using the radial arm saw, even in cases where it probably would have made more sense.  So today, if all went well, I'd get to use the saw for the first time.

Clint and I studied the problem and designed the jig.  We began crafting it out of some nice cherry that I had left from another project.  The concept is that you would clamp the banjo neck to a flat board in a precise position that would represent the ideal 3-degree angle that the neck makes with the banjo head.  Then you would align the board with the blade of the saw in such a position that the saw can be raised and lowered to chew away the unwanted wood and leave the perfectly-aligned concave surface desired.

The first job with regard to the saw was to turn its blade to a horizontal position.  There's a small detent that enables the user to rotate the blade and motor.  With the help of an on-line users manual, we finally discovered that detent and were able to properly align the blade.  Because of the threatening appearance of a spinning 10" blade, Clint refers to this tool as the "death saw."  We treat it with great respect and caution.

We calculated how high to wedge the neck, crafted a clamp to ensure the rigidity of the neck relative to the base board, and put the jig together.  This process took perhaps two hours.  Then we set the jig up on the saw.  It looks so simple once you've figured it out, but we actually put a considerable amount of time into determining the position of the blade in relationship to a restricting fence on the saw table and other adjustments.  When we were done, the setup looked like this:

The business end of the saw is engaging the end of the neck as shown here:

The jig is moved toward the blade until it is in a position where the blade, when raised or lowered, would eat away perhaps one-sixteenth of an inch of the exposed end of the neck.  It is then raised (or lowered) through the entire height of the heel.  Another small adjustment is made, moving the jig another sixteenth of an inch toward the blade and raising the blade through the height of the heel.  This is repeated until the shape desired is achieved.  And when the cutting is all completed, the base of the neck looks like this:

The notch at the bottom of the neck is the slot into which the flesh hoop and tension hoop will fit when the banjo is assembled.  The neck is upside down in this image, clamped to the jig.  The dark horizontal band is the ebony fretboard being pressed against the jig to ensure that the cut by the saw blade will hold the neck in correct alignment with the rim -- that it won't "tilt" to the left or right.

The bottom line -- We now have a system that we can reuse with consistency and accuracy in shaping the base of our banjo necks.  Let's just hope it's not several months more before you hear another update.

Saturday, March 22, 2014

Banjo Boys - Chapter 31 - Finishing the Cherry Blossom Banjo

Photo courtesy of Mary Ann Mead
Official photographer for the Banjo Boys of Fayetteville
Today, Clint was coming up to the shop to see if he could finish up his cherry blossom-themed banjo.  I hoped to get the holes properly drilled in my maple rim and get my brass hardware installed.  I also had noticed that my heel was too "fat" and exhibited some sandpaper scratches that I needed to eliminate.  We both got partway to our objectives.

Clint started by gluing a split in his dowel stick where he had drilled a longitudinal hole for the endpin to screw into it.  He glued and clamped the split.  This is a very difficult kind of break to repair, since the intercellular bond of the wood has been compromised.  Sure
A typical square dowel stick ferrule
enough, when Clint tried to screw the endpin back into the dowel end, it broke along the glue line.  We discussed the possibilities.  A square-shaped metal jacket, forced over the end of the dowel stick would do the job, but how to bend such a piece with the equipment at hand was a mystery.  It needed to have sharp bends and fit tightly around the perimeter of the dowel stick.  We went back to the drawing board.  What if we could find a tubular brass object of the correct diameter?  Clint could round the square edges of the dowel stick up to a point past the split and force fit it to secure the repair.  We proceeded to the local Ace Hardware store where we found a perfectly-sized brass collar.  Clint cut the threads of one end, smoothed it up, rounded his dowel, drove the collar over the first few inches of the stick, and cut it to the proper length.  The repair was made!

The screws that hold the "shoes"
The shoes, hooks and nuts that
hold the tension hoop
I began the day laying out the pattern for the holes I needed to drill in the maple rim that I had already sanded, stained, oiled, and cut to receive my dowel stick.  I had purchased a pre-notched tension hoop from Rickard Banjos in Canada a few weeks ago.  One of the nice features of a pre-cut hoop is that it provides a guide for the positions of the needed holes.  I centered the string cutout in line with the square hole in the rim into which the dowel stick fits tightly, thinking that that hole represents the center line of the neck.  Then I taped the tension hoop to the wooden rim at a level where the holes needed to be for the hooks to work properly.  This was a little trick suggested by Clint.  I carefully marked each hole location with an awl and then proceeded to drill the holes for the tiny machine screws that anchor each of the so-called shoes.  The shoes are drilled and the hooks extend through this hole and are put under tension by nuts that cover the threaded ends of the hook shaft.  These are held in place by hex-headed brass machine screws extending through the rim.

The ferrule repair
The surprise came when I installed the neck again to check everything, only to discover that my dowel rod is just enough off-center where it enters the nack, that it causes an interference between the side of the heel and one of the shoes.  I'm now in the process of reshaping the heel to make it more narrow, hopefully narrow enough to eliminate the interference.

Clint finished the repair to his dowel stick and it came out fine.  He's going to polish the brass and then antique it using some acid solution he has used previously.  He then shaped the nut that goes at the top of the fretboard, glued it in place, and filed the grooves (slots) that will accommodate the strings.  I think he plans to put strings on it this weekend.  We knocked off early, since Clint had a previous commitment for the afternoon.

The finished maple rim

Sunday, March 2, 2014

Banjo Boys - Chapter 30

Bob's partly assembled banjo -- neck and rim now fit together
Clint and I haven't gotten together for several weeks because of many different conflicting activities and business travel.  So today was special and the weather forecast was promising with only a 20% chance of rain and highs in the 60s.  Clint got up here around 8:30, accompanied by Zoe.  Naturally, Sheila and Goldie were excited to see their cousin.  I left them out of their pen all day and they stayed close to the shop.

We first set up to counterbore our holes in the rim and heel into which the dowel rod is glued.  The way this is done is quite clever (I didn't think of this, by the way.).  After shaping the base of the neck where it attaches to the rim, the two major parts, neck and rim, are held in a fixture to maintain their proper alignment.  Then, using an 18" long drill bit, we bore a 1/4" hole in the bottom of the rim, through the opposite side of the rim where it contacts the neck, and a couple of inches into the heel of the neck.  This hole allows the builder to insert a 1/4" steel rod completely through both rim holes and into the neck hole.  The next step is to make a
The Fuller Counterbore
larger hole in the upper part of the rim and the neck.  This hole must have the same axis as the initial 1/4" hole to keep the neck in proper allignment with the rim.  Fortunately, there's a tool that can accomplish this.  It's called a Fuller Type B counterbore bit.  Think of a 5/8" drill bit with a 1/4" hole in its center line.  Add a couple of set screws, and you have the tool needed.  We insert the steel rod into the lower hole on the rim, then lock the counterbore near the end of the rod, then insert the rod into the opposite rim hole, and begin boring.  When the wood chips quit flying, we've bored a 5/8" hole through the upper rim and into the neck.

Next, we shaped the upper 1-1/2" of the square dowel rod into a round 5/8" peg that will be glued into the neck.  The finished product looks like this:

The 5/8" hole in the rim is then expanded into a square just large enough for the tapered dowel rod to slide into.  The square shape keeps the neck from rotating relative to the rim.  We want to keep the fretboard surface transversely parallel to the plane of the banjo head.  The neck will be held tightly against the rim by the attaching hardware we will install later.

The last thing we did today was to cut and install the nut that supports the upper end of the strings.  We are both using black water buffalo horn for our nuts.  The nut groove is trimmed to ensure a snug fit for the nut and then the nut is lightly glued in place.
The finished peghead with nut installed

I spent the last hour or so shaping my heel and staining the entire neck and rim.  As with my previous "Buick" banjo, I used a dark tobacco brown stain.  The amount of "curl" in the maple is really remarkable.  I think it's going to be a very nice instrument.

Clint did most of the same operations I did.  He's trying to finish up his "cherry blossom" banjo as a gift for his father-in-law.  It's really looking spectacular!

'Til next time...

Monday, January 20, 2014

Late Breaking News!

After Clint went home on Saturday, he decided to assemble his rim to see what it will look like with hardware installed.  He had acquired brass hardware and then researched how brass is "antique" finished.  The result is terrific...

Sunday, January 19, 2014

Banjo Boys - Chapters 28 & 29

The shaped base of the neck determines the alignment of the banjo.
The recessed section accommodates the flesh hoop and tension hoop.
Clint has been up twice and I haven't taken a single picture or written a single word.  He's been working hard on his "Cherry Blossom" banjo.  It's going to be a spectacular instrument.  He finished his inlay in December and came to the shop on December 28th to cut his fret slots.  We couldn't find the miter box that we had built a year ago to cut fret slots, so we made a new one.  He finished cutting the slots and took some tools and sandpaper with him to finish shaping the neck at home.  When he got here yesterday, a lot of progress was evident:

  • He had finished sanding his cherry rim (with one Honduran rosewood edge and one ebony edge) and had applied several thin coats of polymerized tung oil.  It looks incredible!
  • He had drilled the holes for all his tensioning brackets,
  • He had finished shaping the neck and applied tung oil to it as well,
  • He had installed and almost finished his frets.
A polished spoon-hook
When Clint was here in December, I discovered that my neck had bowed due to the tightness of the frets in their fret slots.  The lateral pressure exerted by the tangs was substantial enough to cause the entire neck to develop a curve I could see if I looked down the length of the fretboard.  I removed those frets.  I also dismantled my Buick banjo to polish the spoon
The jig used to shape the
 base of the neck
hooks where they exhibited burn marks from the brazing operation that attached the spoons to the square nuts needed to tighten the head.  

The main challenge for today was to set up the necessary jigs to shape the base of the neck where it fits against the rim.

The dowel stick blanks
We decided to start by cutting our dowel stick blanks out of the waste piece that results from cutting out the back profile of the neck.  By using this scrap piece this way, we ensure that the dowel rod has the same grain and pattern as the neck.  We set these aside and began the setup for the neck shaping.  

After about two hours of careful measuring and remeasuring, both necks are shaped.

The next step was to drill the pilot hole from the bottom of the rim through both sides of the rim and into the heel of the neck while holding the parts in perfect alignment.  We were able to complete this operation on both Clint's and my banjo.

I've ordered a new counterbore bit to enable us to cut the dowel hole in the neck and if it arrives by next weekend, we'll probably do that next.  Stay tuned...

Monday, December 23, 2013

The Quest for Perfection...

Last week I went out to Dan Shady's shop and he had my banjo out on a workbench.  We had finally acquired the square nuts that he wanted to braze to the backs of my spoon-hooks so that we could insert screws into the nuts to tighten the tension hoop, thus stretching the clear plastic head.  From this angle, the banjo looks fantastic!

Unfortunately, on the other side of the banjo, there are three empty brackets.  Dan indicated that there were differences between some of the hooks and he didn't feel right about having unlike hooks on such a beautiful instrument.  So I did what any red-blooded American banjo builder would do -- I got on eBay and found some more World War II-vintage Navy spoons.  I could only find two with the "USN" imprint, but I found two plain ones.  I'll make hooks out of all four and once they're finished I'll put the two plain spoons adjacent to the neck attachment.  Everything will be symmetrical.  Here are the new "hook-blanks."

Saturday, December 14, 2013


One of our colleagues at work, Jay Puckett, mentioned to Clint and me that he had a couple of friends who were taking banjo lessons.  We agreed to bring our banjos in on Friday, finished or unfinished, so these fellows, Mike Greene and Bob Francis, could visit and see what we had done.  They showed up and Mike played Clint's finished instrument: