Manufacturing Thor: Part 6

Part 6: Compound Radius Fretboard

Thor’s fretboard has compound radius, with a radius of 304 mm (12″) at the nut and 456 mm (18″) at the 24th fret. Typical fretboards have a uniform radius, which is less than ideal for low action because the strings must be parallel to each other for consistent string height. But they are not. The fretboard is tapered. The strings are closer together at the nut and wider apart at towards bridge.

Compound radius fretboards follow a conical surface, as opposed to cylindrical. This allows for lowest action without string buzz. This article on Stewmac goes into greater detail: Compound Radius: Explained.

Of course, we made our own jig for precise compound radius shaping of the fretboard. The jig saves time and ensures consistent results without the need for tedious sanding with a sanding block.


A router guide (top) swivels along an axis supported by two pillow blocks, one end 304 mm (12′′) below the fretboard’s top and the other 456 mm (18′′).

Here’s a quick video of the jig in action:

And the result, after fret and nut slotting (coming up next!):


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1 year ago

Whats your method for leveling frets on a conical fretboard?

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1 year ago
Reply to  Joel de Guzman

Hmm….I’ve explored and had a hard time with this approach. IDing the first set of high frets and leveling them individually often just leads to adjacent frets being high after correcting the first set. Have you found a way to avoid this?

1 year ago
Reply to  Joel de Guzman

I use jescar SS, CNC my boards and sand them with a matching radius aluminum block, ridiculously carefully – I even rigged up my CNC to do the sanding for me to ensure perfect alignment and avoid any unwanted influence from the mechanics of the human body. Unfortunately it just took way too long so I had to try to go back to manual sanding to save time.

I get my fretwire from a supplier that pre-radiuses for me, maybe they’re not doing an accurate job with the radiusing….Ill have to look into it.

Its funny, I refused to level for years trying to make this approach work, then gave up thinking my results were subpar without leveling, now you’ve got me headed back down that rabbit hole again, ha!

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