There are two main benefits from taking and recording measurements. The first is establishing a baseline from which to work. The second is saving time.
Every guitar that hits the bench has a different set up. Some have the strings lying on the frets, others have enough relief that they're good for archery practice. While you can get some general ideas sighting them up the tech is starting from a different spot every time. By establishing a baseline the tech is starting from the same point.
Pick an arbitrary, but relevant and useful point. On four and five string basses I set the relief quickly to .012" and the string heights to 6/64" and 5/64" bass and treble sides respectively. You can use whatever you like. That is considered by many to be a medium low or "factory" set up. That takes about two minutes. (I've timed it. Time is money in the shop!) This is all part of the evaluation. It answers a bunch of questions.
- Does the truss rod work correctly?
- Does the neck need to be flexed when adjusting the rod?
- Is the neck angle correct?
- Where is the low point on the neck?
- Ski jump?
If all is well, play and listen for buzzes. If it does, figure out why and fix it. If it doesn't, start to lower (or raise) the string heights according to what the player wants. If it's your guitar, do as you will to get it to where you want it.
The benefit from this method is that it is easier to evaluate each instrument starting from the same point.
When the set up is completed, the finished measurements are recorded for the instrument and the player. Now the instrument set up is specified.
The benefit of having a record of what the ideal (for the player) set up for an instrument is that you can skip the arbitrary baseline set up and simply return the instrument to the known good set up. Sometimes it will require a tweak. But sometimes you're done as soon as you put it back to the recorded specifications. Set the intonation and play.
Talk about saving time!
