Starting a guitar building process may start with ideas and sketches but as soon as it moves to more practical and actionable planning, we need to have the right size, shape and proportions. Good and accurate measuring tools are critical to getting a playable instrument. Most of these tools are not unique to Lutherie but the right variation or adaptation of it can sometimes make a big difference.
As much as I love a good measuring tape, the comfort and accuracy of a ruler will make a difference. On top of that a ruler is also a straight edge. When it comes to rulers, size does matter, and the ideal ruler will cover the length of the guitar or at least the length of the ‘guitar scale’. Without going into too much detail, that is the length between the nut and the bridge. From the short Fender Jaguar at 24” (61cm) to the longer 7 string Ibanez at 26.5” (67.3cm) a decent 36” (91.44cm) ruler will be great. A pair would be even better when placing and measuring the neck. A couple of shorter ones 20” (just for the neck) will also be very handy as the extra length can be cumbersome when not in use.
In short, a couple of 36” and a couple of 20”
Notched Straight Edge
This one is really Luthier specific. The notched version will have little indents so when laying it on the neck the actual edge will sit on the fingerboard and not on the frets. Most Notched Straight Edges will come with two different sets of notches, one on each side. One side will match a Fender style scale and the other Gibson style scale. This will work with the majority of guitars but pay attention if you are going for a less traditional guitar scale. A must have for any neck building or any other neck adjustment.
Micrometer Caliber (Preferably digital)
The Human eye is limited and sometimes you want to be precise. Precision is not over-rated. For most cases the analog one will do fine but if you don’t have a digital one, trust me you will love it. Definitely needed for fretting and they are not that expensive today.
This gauge is used mostly to check you’ve actually reached the desired radius when sanding. It is also useful to gauge the strings themselves when setting up, they should follow the radius of the neck to get consistent/ correct action.
There are two types of Radius Gauges: T shaped and square ones.
The T shaped ones are more versatile as you can slip them under the strings and check the radius accurately without removing the strings. Handy for doing repairs and setup.
The square ones (each one can have four different radiuses) are a bit more comfortable to hold and handle, but just may be me… They can also be of metal, Plastic or even printed out and pasted on cardboard.