Free radius gauges and their many uses

I talked a while back about compound radius fingerboards (where the radius of the board changes from one end to the other) and I briefly mentioned using a radius gauge to check and set radius.

I thought it’d be useful to go into a bit more detail about that particular job and to look at some of the other ways a radius gauge can be not just useful, but indispensable.


Download free radius gauges

Before we start, you can download a printable set of radius gauges for freesies if you like. Just paste them to a piece of card (a cereal box works fine) and cut them out. Voila, radius gauges.

Just enter your info below to get your free radius gauges…

So, back to those radius gauge jobs.

The obvious one first…

Checking fingerboard radius

When you’re setting up a guitar or bass, it’s great to know the radius of your fingerboard. This can be even more important for a compound radius board.

Also, if you’re ever doing work on an older guitar, you’ll definitely want to check the board for consistency. Sometimes you’ll get instruments whose radius isn’t quite what it should be, and even instruments where the radius is weirdly inconsistent all along the neck. These issues might call for some corrective work.

Some of the time, these variations in radius are due to instruments having had some fret work in the past. For instance, you can find a guitar with a radius that’s been altered from ‘stock’, either deliberately or accidentally, during a previous refret.

However, it’s not unusual to see oddness like this on instruments that have never been touched from the factory. It’s more common on older instruments where some irregularity crept in as the board was being hand-levelled or radiused, but it’s not completely unheard of on newer guitars too.

What I’m saying is: check it.

How to check a guitar fretboard radius

Checking radius is super easy. With the strings removed, just use your radius gauges to find which best ‘fits’.

Checking the radius with your free radius gauge. ;-)

It’s not rocket science although, occasionally you’ll come across a board (usually an older instrument) that doesn’t quite match any of the common radii. In this case, find the closest ‘standard’ radius and, if you’re in a position to work on the fingerboard consider whether it’s worth modifying the board to that standard radius. If the ‘incorrect’ radius is consistent along the neck, it’s probably not a major disadvantage and you may not need or want to worry about it. It’s worth knowing and considering though.

If your fingerboard radius wanders randomly over the length of the neck, however, that’s a more compelling case for standardising it. You’ll probably end up with a better playing guitar at the end but, again, give it some thought — especially with a vintage or valuable instrument.

Set consistent action across all strings

For a nicely playing instrument, it’s important to set the action of each string so that it ‘graduates’ evenly across the fingerboard. Having string height match the radius makes a big difference to the setup of a guitar or bass.

On instruments with individually adjustable string saddles, I usually recommend you set the first and last string action to be about right. Then the ‘middle’ strings can be set and a radius gauge is a good way to go about it.

Setting guitar bridge saddle height for a consistent radius

If you’ve got something like a Gibson, fitted with a tun-o-matic bridge, don’t assume you’re in the clear. You’d be surprised how often the radius on these bridges is either inconsistent or doesn’t match the fingerboard. It’ll involve a little filing but now’s your chance to check and put it right.

Setting pickup pole-piece height

Many pickups have screw pole-pieces that can be raised to adjust their distance from the strings. Doing this lets you balance the output of each string so that none is louder or quieter than the others.

Most of the time, these pole-pieces are left flat across the pickup but adjusting them will give you a more even sounding instrument.

Setting humbucker pickup screw pole height

The basic way of doing this (and if it’s done on your guitar, this is probably how it was performed) is to match the pole-piece height to the radius of the strings/fingerboard.

Your radius gauge will come in handy for matching pickup pole-pieces to string height.

Radiusing the bottom of a Fender-style nut

On most Fender (and many Fender-style) guitars and basses, the nut sits in a slot that has a curved bottom. Put another way, the nut slot is cut to match the fingerboard radius, so it’s bottom is similarly arced.

This means a replacement nut must have an identical curve cut in it for a sound fit.

Marking curve of nut slot on bone nut blank for Fender replacement.

Marking a nut for installation in a Fender neck's curved bottom nut slot

Your radius gauge makes it easy to identify the right size and to mark out the bottom of your new nut.


Radiusing the top of an acoustic saddle

In the same way you want your electric guitar’s strings to follow the fingerboard radius, it’s just as important for your acoustic guitar too.

Check your acoustic instruments too. You might need a little saddle shaping to get things juuuust right.

The bottom line

A set of radius gauges should form part of the toolkit of anyone doing any sort of guitar setup.

If you’re going to be doing this regularly, it might be worth buying a good set but my free, downloadable, radius gauges will definitely do the trick for a while.

Enter your info below and go get ‘em.