Compound Radius Fretboard

      Alpha, Bamboo, Carbon Fiber, Construction

I am more of a melodic lead player and I play lead more than chords. I prefer slim necks with flatter and low action fretboards that do not “fret out” with aggressive string bending —yet one more reason why I am not fond of the ever so popular Stratocaster. I am really inclined to build my next guitar that’s built exclusively for lead guitar playing with a totally flat fretboard, like a classical guitar. But this one is destined to be more conservative and general purpose so I’ll keep the fretboard curvature.

The question is how much curvature? The modern Strat has an aggressive 241 mm (9.5″) radius while Gibsons have 254 mm to 304 mm (10″ to 12″) radius. Modern Jacksons, on the other hand, have what’s called “compound radius fretboards” which are really conical fingerboards which start out with a smaller radius at the nut and gradually get flatter (bigger radius) towards the other end. The Jackson is definitely one of my favorite axe in my arsenal. And, for this design, I will definitely have something based on the Jackson. The radii of the curvature starts at 304 mm (12″) and ends (at the 24th fret) at 456 mm (18″).

Compound radius cutting jig

For this to happen, we need, you guessed it: yet another router jig. The router rides on a platform that pivots on a stainless steel shaft which is oriented on an angle corresponding to the conical section with our desired start and end radii (304 mm and 456 mm). Swinging the mechanism back and forth will give you the correct radius at any given point in its entire length, thereby guiding the router over the block to be cut into a fretboard. This web article details this jig quite well: Compound Radius Routing Jig for Guitar Fretboards.

Now we sandwich the fretboard with 8 layers of carbon fiber laid up with laminating epoxy; 4 on top and another 4 at the bottom. The fretboard is vacuum bagged to remove excess resin and to ensure that there are no air pockets or bubbles that can ruin its sonic integrity.

Bamboo fretboard ready for layup

4 layers of carbon fiber

Bamboo fretboard sandwiched in between with another 4 layers on top

Vacuum bagged. Excess resin oozing out.

After 24 hours curing, it’s time to slot the frets. I love jigs. Jigs make tricky tasks easy to do accurately. Inspired by StewMac’s fret slotting miter box, I use another jig for cutting the fret slots. Finally, we trim the sides using a fretboard template with a pattern following router bit.

Released. Nice and smooth! Ready for trimming and slotting.

Slotted and trimmed

Further Reading

  1. Guitar Fretboard Radius
  2. Compound Radius: Explained
  3. Compound Radius Routing Jig for Guitar Fretboards
  4. Fingerboard
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Denny Rauen says:

Hello Joel,

Nice of you to share all this with everyone. It amazes me to see the different apparatuses and processes fellow luthiers use for creating the conical fingerboards. I am contacting you in my effort to touch base with fellow luthiers using the compound radius in an effort to clear up confusion about the creation of my idea.

What I originally called the “Multi Radius Fingerboard” in 1978 was renamed by Warmoth in the 1980’s and subsequently they are often given credit for creating it. I built many guitars in the late 1970’s, 80’s & 90’s using my “Multi Radius fingerboards and their still around along with the owners.

Much like you are doing here I shared my creation with the entire world of luthiers by publishing it in two different journals, American Luthier #8 and String Instrument Craftsman. This was a personal choice I made and it gives me great satisfaction to know that I have given something back to a community that has give me so much. 

Over the years my idea has been widely used with no company or individual luthier ever paying a single penny in licensing fees, as I intended. It was important to me to share the idea many years ago and as I have become more knowledgeable about computers and the internet it's important that I clear up the misinformation about creating multi/compound/conical radius fingerboards. Certainly my conical radius fingerboard is not the end of the story when it comes to fingerboards but it is part of the story and I would appreciate it if you would consider some mention of my name regards to creating the compound radius on your posting.

Your consideration is much appreciated and best of luck with your instruments.

Here are a few links to document and verify my comments    click the link in the bottom half of page


Denny Rauen

Joel says:

Thanks for dropping by. It's really nice to see fellow luthiers here! Thanks for the info, Denny. Next time I do an edit, I'll definitely add that info plus a lot more updates.