LeftyBassist.com

first HD foam proofing body of the new 6-string single-cut fresh off the CNC. it carries a lot of the styling from my original prototype constructed and in testing since 2007, but I've also updated it -and- added a full 24-fret neck (the original had a 22-fret neck)

the angled headstock will be identical to the 24-fret double cut model that's about to enter production. images of that are here in a thread dedicated to that design. the rear contour will also be identical to that, but the heel will be significantly different due to this being a single-cut design

the first commissioned build will be a 6-string lefty, and eventually headed to a player who doubles in the Country and Jazz scene. estimated delivery is right about NAMM time

all the best,

R

the first wooden proofing body has been completed. it has yet to be detailed, so it's still pretty rough compared to what would head off for paint.



now it's time to turn my attention on finishing the last couple neck CAD design details so I can focus on generating the CNC code and initial proofing units

all the best,

R

Is that straight out of the CNC machine? If so, mighty impressive! It appears that most of the contouring and rounding is already done for you. Looks like you're really getting to know your CNC!

that's an almost CNC only status image - I cleaned all the sharp edges with sandpaper to remove the uncut wood fibers, and I also radiused the side edges at a router table prior to snapping the images. all else is pretty much right off the CNC. There's still a couple hours of hand detailing/sanding to do before this is ready for the paint shop, but that's difficult to see in the images since they tend to hide the tool marks


I should also share that the neck for this model isn't going to be mounted with any wimpy wood screws, nope, no way. this joint will be fastened with five 5/16-18 cap head machine screws that mate with steel nutserts installed in the neck prior to attaching the fretboard.

if you look closely at the image below, you can also see that I will be using threaded inserts for the control cavity cover



back out to the shop

all the best,

R

what's the towing capacity of that bass??

I'm figuring this is about 3/4T capacity with a 250# tongue weight limit

R

so what's a bass body without a neck to accompany it?

I have the CAD work for the neck design completed, and am working some initial CNC tool path generation to see how best to cut this design.



Once I have a reasonable handle on this I'll then be creating a new set of hold-down fixtures so I can accurately locate the various stages of the neck blank while clamping it securely in a way that won't cause a collision with the CNC spindle head. Once the tooling is designed and built, I can then start work on optimizing the CNC cutting paths for each tool type needed and then get to work cutting necks

Side note: since I'll be offering this design in both 5/6-string and righty/lefty configurations, the hold-down fixtures will need to be designed for quite a bit of flexibility. It will be even greater if these new fixtures can also be used together with the 4/5/6-string double-cut neck so I can minimize my tooling investment (which resultes in a lower investment cost that's distributed across a given nmber of basses, and once accommodated then becomes my gross profit margin per unit)

all the best,

R

+1! Rod, you just continue with not only your attention to detail, but pushing the envelope in development.... kudos to you!

thanks!

I had opportunity this morning to cut the first neck heel/contour testing proof, and achieved results beyond what I had hoped for.



With this test completed, I will make a few minor adjustments and then cut another proof out of Maple so I can verify how much tool deflection to anticipate this neck heel to impose while cutting. After this I’ll move forward and do a couple proofing cut parts for the headstock, and once that’s good I’ll proof out a couple of complete neck shafts (minus the trussrod and carbon fiber stiffening bars) so I can validate the design and my custom alignment jigs and fab workflow

all the best,

R

Once again Rod, outstanding attention to detail! It also makes me realize how much time goes in to R&R, which has to cut in to your workload time... obviously you are concerned in furthuring every aspect of your business with the utmost care and professionalism - and it shows in the beautiful basses you build!

OK, enough head-swelling rhetoric... back to work!

the R&D time definitely cuts into regular build time (or increases workload significantly, however you wish to think of it), and it also sucks up a fair amount of $$$ resources for proofing materials and tooling ... sure the Barney bodies are inexpensive HD foam costing under $10 per body, but the wooden bodies (typically made from Poplar) have all of the woodworking labor time and tooling costs (wear/tear, maint, cutter sharpening, etc ...) of a real production body at about 50% the cost of Alder.


If I simply forget my hours spent on R&D, a new body design takes roughly $450 of materials minimum to bring to a "ready to loan out for a session" prototype readiness ... a new neck is even more thanks to carbon fiber stiffening bars, frets, trussrods, nuts, etc ...)

When I'm convinced the design is where it needs to be, then there the cost of several "session ready" prototype units (again forgetting about my time investment and looking only at the wood, hardware, electronics, paint, strings, etc ...) which need to be completed and put into the hands of the bassists on my test panel (of which I am typically the first field test subject) with the finish needing to be every bit as good as a production bass because of where (studio & live) these prototype basses are tested (case & point: a new prototype was utilized in several recent studio sessions at Scott Anderson's studio here in Seattle ... anything going there has to be absolutely perfect because I never know who else will be hanging around that session) ... on an active electronics bass, I'll have waaaaay more than $1K into each of these basses which, if they flop in the hands of the review panel players, have potential to become nothing more than expensive firewood.

And then, once that new design is completed and ready for production release it still needs to be marketed so it can find a home in the hands of those first few daring bassists willing to take a leap of faith on a new model they have never seen in a guitar shop anywhere.


you really have to love taking significant financial risks and the craft of building instruments to keep in the business as an independent instrument company. the big guys have their dealer market channels wrapped up and fortified. small companies have to choose between spending $$ on marketing, or R&D, or some less than desirable compromise that finds funds for both marketing plus R&D ... the even smaller shops have the equally difficult choice of building production instruments or working R&D on new models while letting their time from order to delivery grow a bit


all the best,

R

massaged a few subtle changes into the neck design, including the swap to a heel adjusted dual action trussrod vs. my original design of a headstock adjusted traditional style single action trussrod.

here's a snapshot of the body and neck CAD models assembled together without any hardware attached (I need to re-do the front image ... the angle of the image makes the body look a little wonky IMO ... and wonky it definitely is not)





I'll spend the next few weeks working on new hold-down tooling and fab workflows so I can cut out a couple proofing necks. once all is good to go it'll be onwards to the first couple productions in prep for NAMM in Jan

all the best,

R

I finally have the rear contour transition surfaces flowing smoothly and cutting like butter ... here's a quick peek at how the transition looks after -very- minimal post CNC clean-up. The rear contours and transition are comfy enough to play all the way back to the bridge side of the neck pickup (if the frets actually went that far)



Time now to turn my focus onto cutting a proofing neck section for the headstock/neck transition region …

all the best,

R

given loads of "think the process thru from start to finish" time while developing the CNC tool cutting paths, I've developed a strategy of three 'working' positions that fit within my CNC envelope (large purple rectangle area)



each position has multiple steps performed at it before the neck is promoted to the next position.

here's a brief of the steps:

prior to securing to Position 1, I will have joined the fretboard face and rough cut much of the excess thickness from the rear side and headstock face leaving about 1/8" of material to be cut away via CNC (my neck blank glue-up makes two back-back necks that get cut apart prior to this step)

Step 1 (Pos 1) is to cut the rear flat face leaving a bit of excess stock for a later step, and then drill alignment pin holes

Step 2 (Pos 2) align on the pins, and machine the fretboard face flat, cut the headstock face to 7 deg, cut the trussrod and carbon fiber stiffening bar slots, drills fretboard alignment pin holes, and drill holes for tee nuts

Step 3 (off CNC) epoxy stiffening bars into neck slots, and then clean up fretboard gluing surface post cure

Step 4 (Pos 1) align on the pins, machine the heel face, rough and detail the rear neck contour, rough the rear headstock contour, and cut the neck shaft outline before drilling alignment pin holes for mounting the fretboard

Step 5 (Pos 3) align on the pins, and then machine the final headstock thickness, drill tuner holes, and then cut the headstock outline


I'm fabricating the positioning blocks this week, and hope to have everything ready for a full step-by-step test run the following week. I have to admit it - utilizing a CNC requires tons more brain power and process planning when compared to simply working an individual neck build with traditional hand and power tools ... but the long-term payoff in enhanced quality and repeatability is worth the added work for cases where I plan to build more than three or four of a specific design


it's fun to have all this coming together

all the best,

R

All of the slots on this build will be precision cut via CNC so that they follow the contour of the fretboard vs. the traditional table saw slotting method (deployed by most industry builders and large luthier supply companies offering pre-slotted fretboard blanks) which cuts a flat slot in the fretboard prior to the radius being carved. The table saw method leaves a significant gap under the fret in the center of the fretboard. The CNC cut method cuts the fret slot parallel to the fretboard radius, ensuring a well seated fret along its entire length. the below images reference the curvature of a 'rather flat' 16"R fretboard



On the plus side, utilizing a well tuned CNC provides an unmatched level of precision not possible with the table saw sliding bed technique … and it opens the door for me to slot to custom scales (say a 33” scale should a customer want something a little easier on the hands but still with a traditional sounding D/G string for slapping) without the ghastly cost of machining a custom slotting template which may only get used once. The CNC method also allows me to easily cut fret slots following the fretboard with a compound radius (i.e. a rounder fretboard near the nut that morphs to a flatter radius towards the bridge)

Cutting slots via CNC is significantly more expensive to do thanks to the delicate nature of the 0.022” diameter bit utilized to cut the 0.095” deep slot … it’s not unusual to break one (or more) of these $30 bits while slotting a fretboard In addition to cutter breakage, utilizing micro bits like these requires the use of ultra precision router collets and collet nuts with a total run out of less than 0.0002" (0.005mm), plus a special spanner wrench to tighten this $200 nut/collet set

all the best,

R

neck blanks from a softer wood ready to cut the initial proofing parts to validate tool paths



the rear side is machined level as a reference face for the next operation



an elevated hold-down jig is fitted with alignment pins to precisely position the neck



the neck is flipped onto the hold-down jig and readied for the next machining steps. since the headstock is not yet roughed, I simply shim the end of the neck blank to prevent flexing during the next machining process



more to come ...

R

Rod, as a finish carpenter, I'm enjoying your updated posts, and appreciate your attention to detail in spelling out all of the steps it's obviously taking to produce your latest model. I'm curious though at to how you are keeping the neck-blank secured to the hold-down jig - small pins on the underside to keep it from moving?

thanks - as one who has spent considerable time as an instructor, I enjoy the process of working thru a solution and doumenting the workflow so others can also learn



precisely - the pins serve to allow for precise alignment from one process step position to the next. in addition to alignment, the pins also serve to take on a portion of the shear load when machining. in this proofing phase, I'm utilizing industrial double stick tape to secure the parts in position ... but once I have everything proofed, I'll be remachining my hold-down blocks to include routed channels for vacuum clamping the parts securely onto the block. between the vacuum's downward suction and the pins assistance in resisting shear stresses, the neck will be snugly secured onto the block without the need for any additional securing compound.

in the event that I have a part which doesn't have enough surface for vacuum clamping, I'll need to devise a method for additional mechanical constraints that are bolted to threaded holes in the CNC table

all of this, of course, to facilitate an easy and repeatable on/off load for the neck in each of its machining positions ... amd increased precision combined with quicker mount/dismount equals higher quality at a lesser net cost

this should become more obvious as this thread continues thru to eventually include a video of one of the production necks ... but there's still a load of work to be done before I'm ready to go Speilberg on all y'all

all the best,

R

Progress continues on the proofing neck Tonight I was able to rework the tool paths to detail the fretboard mating face of the neck shaft as well as the front headstock face. Everything is progressing without a hitch, and turning out to be right on the money dimensionally – yes!



The next steps in this position are to
• Cut the trussrod slot
• Cut the carbon fiber stiffening bar slots
• Drill the fretboard alignment pin holes
• Drill neck blank alignment pin holes

Once these steps are completed I’ll flip the neck into the next position so I can begin machining the rear contour. It’s this next step, with the abundance of wood removal for the rear contour, where everything is really going to look like progress is happening

all the best,

R

the heel mating surface, rear contour, and back face of the headstock are now cut, leaving a few holes to drill prior to cutting the neck shaft perimeter and progressing the neck to the final working position. if you look closely you can see the volute peeking up where the neck rear contour meets the rear headstock face



all the best,

R