Ron Thorn talking about the impact of CNC machines

Malkav

I found a thread on another forum in which master luthier Ron Thorn talks about CNC machines and how they make production of guitars easier and also more accurate. I figured I'd share because it kinda helps dispel some of the myths about CNC machines and this odd belief that somehow they churn out fully completed guitars, even in large scale production there is far more handwork done than most people would think. Also it allows for guitars to be more accurately made, I'm personally of the opinion that CNC assisted production > handmade. I'm not saying that it's impossible for a master builder like Ron Thorn to make a guitar entirely by hand and not have stunning results but in the long run I think if I were ever getting a custom I'd insist on having CNC machines play a part in the production, especially with regards to fret placement.

Originally Posted by Ron Thorn
I'm game.

First off, there is no shop, large or small, that is entirely CNC. It does not exist. I think most individuals would be surprised by what a guitar component looks like when it comes off a CNC. It is no where near complete, there is still plenty of hand sanding, fitting, etc.

Here's a break down of what I do with the CNC and "by hand".

CNC:
Fretboards - you asked "why
they've gone to the CNC and what aspect of things is better". The fretboard is so brutally important that it is ideal for CNC accuracy. I perimeter, slot, radius, and rout for inlays all in one set-up on the CNC. Than insures spot-on fret slot placement (VERY important to the quality of the guitar), consistent radii including compound radiusing, and inlays that are very tight and free of sloppy filler/gaps.
Total time on the CNC: 20 minutes

Necks - Once the blank has been bandsawn ("by hand") to an oversized shape the CNC will machine the neck carve, perimeter the neck and heel, shape the headstock, drill for tuners, rout for truss rod and rout for logo & purfling. This is done through 6 different set-ups.
Total time on the CNC: 1 hour, 45 minutes.

Bodies - The CNC performs all cavity routing (top & back), neck pocket routing, perimeter, top carve, and bridge location holes. On a pivot style trem, such as a PRS trem, the location of those 6 holes must be perfectly inline to prevent binding of the trem during use.
Total time on the CNC for a body with carve top: 3 hours

Inlays - Production inlays, such as my Firesuns and "T" logo, are cut on the CNC for a perfect fit into the routes on the fretboard and headstock. I also "rip" my purfling strips on the CNC too.
Total time for one guitar's worth: 15 minutes

Components - I machine my own 1-pc. brass tremolos, pickup covers and rings, knobs, back plates, truss rod covers, and jack plates.
Total time worth: Approx: 10 hours.
Granted, all of these parts are "custom" for my guitars exclusively. I could purchase all of these parts from guitar supply shops but prefer to make my own.

None of the above times include any programming, set-up or material preparation...all of which are done "by hand".

_____________________

"By hand"
This term, I assume, includes feeding or pushing the component through a power tool such as a planer, jointer, drum sander, bandsaw etc.

Fretboards:
Pre CNC: The wood is bandsawn to an oversize thickness and feed through a drum sander to flatten.

Post CNC - The fretboard needs to:
Have the side dots drilled and glued in.
Inlays and purfling glued in.
Glue the board to the neck blank.
Level and true the board.
Fret and fretdress.
Total time "by hand": 13 hours for the above operations. My fret preparation (cutting to length, nipping the tang, grinding the tang), fret installation and dress is a total of 6 hours alone...no CNC for any of those operations.

Necks:
Pre CNC:
The wood is milled and rough cut to shape, using tracing templates, on a table saw and bandsaw before it gets to the CNC.
Post CNC:
Install the truss rod and filler strip,
blend the neck into the fretboard,
inlay logo and purfling,
final shape the neck carve to spec using rasps, spindle sanders and lots of elbow grease sanding then sanding some more,
gluing the neck into the body.
Total time "by hand": 8-10 hours easily.

Body:
Pre CNC:
Split top, joint edges, bookmatch glue together, sand to thickness.
Mill/sand body to thickness.
Locate and glue top to body spread then sand and drill locating hole for the CNC.
Post CNC:
Inlay purfling.
Drill for controls, side jack, wiring channels.
Radius back edge on router table.
SAND from 150 grit to 320/400
Total time "by hand": 10-15 hours depending on the wood species.

Paint:
Prep, mask off, stain, seal, color, top coat, lots of sanding in between, lots of sanding after, buffing...the list goes on. No CNC for these ops.
Total time "by hand": 28 hours if all goes right the first time...it never does.

Assembly:
Installation of components (tuners, pickups, bridge, etc), wiring, cutting the nut, set up.
Total time "by hand": 6-8 hours

The above is only visually productive acts, not including ordering wood and components, e-mails, shipping, and just plain running the business.

_______

So, if we deduct the custom components and use off the shelf bridges, pickup rings, etc. The average total time is:
CNC: 5 hours, 20 minutes.
"By hand": 69 hours, 30 minutes.

I consider my shop to be fairly state of the art, I have a large HAAS CNC for the woodwork, and 2 smaller CNCs for the pearl inlay work. The only additional automated CNC-type machinery would be a Plek and a robotic buffer. I could see that only reducing the "by hand" total by a couple/few hours at most.

Not mentioned would be a custom one-off inlay that I, or my father, would do "by hand" with a jeweler's saw and a mini router. The time spent on that could be from 45 minutes to 100s of hours depending on the design.

However small in comparison those 5 hours, 20 minutes seem...they are VERY important to the outcome of the guitar. Accuracy and consistancy are unmatched. There are features, such as my double offset purfling, that just can't physically be done by hand. Fretslots accurate to within .0005" of an inch...heck, the wood will expand or contract more than that by the time I turn the lights off in the shop at the end of the day...but it's good to know they are as accurate as can be.
Inlays that are gap free and clean are important to me. I'm not a fan of filler and I don't want that to be a part of my product. Even with hand cut and routed inlays, I feel we are one of the best at making them tight and clean.

Can I build a guitar with out a CNC, sure.
WOULD I now if I didn't have one...I doubt it, because I would always feel the guitar isn't as good as it can be WITH the help of a CNC.
There you have one take on it from a CNC builder.

Ron Thorn
Thorn Custom Guitars & Inlay

"Powered by HAAS...and loving it "

Bob-Dubery

The thing with small custom shops is that they are custom. In situations where everything (or potentially everything) is bespoke then CNC might not be very handy. But for high-end guitars it should be a good thing. Larrivee use CNC for quite a few tasks, but not, as you say, for everything. Their necks are cut from blanks on CNC machines but they fit them by hand.

CNC should give you the ability to reproduce a design reliably to a high degree of tolerance. This should mean that modern guitars are better built than pre-war guitars. People like pre-war Martins for example, but they vary a lot because tolerances were so wide. The necks, in particular, are quite variable (and intonation can be out). These days, with CNC, they should be able to produce necks with very consistent dimensions.