Making Guitar Setup Measurements with Bad Eyesight

Doing a setup on a guitar or other stringed instrument requires many measurements where a small distance, for example, 1/64th of an inch, can have a large effect on how well the guitar plays. This post shares some of the tricks I use to overcome my vision problems when setting up a guitar. If you have trouble reading the smallest divisions on a six-inch ruler, maybe these ideas can help you.

I am over 70 years old and have macular degeneration in one eye. My progressive eyeglass prescription corrects the vision in my other eye, but to be honest, I don’t see as well as I used to with that eye either. It’s not just old people who can have vision problems, although the probability of problems increases with age. These problems have slowed me down but not stopped me from setting up my guitars. Note, I’m just a guy who loves guitars, not a luthier or a guitar technician.

Useful Tools

The most useful measuring tool I’ve used for decades is the six-inch steel ruler. The above image shows two of my 6-inch rulers, one with millimeters on one edge and 32nds of an inch on the other. The backside has a conversion chart from 64ths of an inch to decimal millimeters. 

The upper 6-inch ruler also has two scales but both are in fractional inches of 32nds or 64ths of an inch. The back of this ruler has conversions from fractional to decimal inches,

Another useful tool is the Stew-mac String action guide. It has multiple scales, all in inches but a metric version is available. Personally, I prefer the 6-inch rulers if only my vision would allow me to see the markings.

A feeler gauge is rarely needed for a setup but can be used without much problem from eyesight. The most common uses of feeler gauges are to measure relief when adjusting the truss rod and when checking nut height.

My newest toy which has solved some of my problems taking small measurements is the digital calipers. Although luthiers often use calipers when building or even repairing guitars, they are not much used for setups. However, I find they are a great tool with the caveat that to use the caliper you need to do arithmetic. A calculator will be useful.

So far, the only tool which specifically addresses my vision problem is the digital caliper that has nice large LCD readouts of the measurements. What would be helpful is magnification and better lighting. There are many ways to provide both but the one I’ve chosen is visor with lenses and LED lamp.

The last item that I’ve used to overcome my eyesight problems is the camera in my phone. Although not required, it is helpful to combine the camera with a small tripod to hold the phone.

Example Measurements

Saddle height

I’m starting with this example because I just changed the saddles on my Telecaster. Setting the saddle height is an adjustment that adjusts the action measured at the 12th fret. If you need to adjust your action, you would not start here. But if you are replacing your saddles as I did, then it makes sense to roughly adjust the string height coming off the new saddles before moving on to measuring the action at the 12th fret.

I used the depth gauge part of the calipers to measure the height from the bridge to top of each string where the string comes off the saddle. Most setup measurements are made from a fixed reference such as the top of a fret to the bottom of the string. But in this case, I first measured the saddle heights of the old saddles and, after replacing both saddles and strings with the same gauge strings, I could measure to the tops of the strings for my rough height adjustment.

If you change string gauges as well as saddles, then you need math, but only simple arithmetic.  

In this example, I measured 0.3700 inches on the 6th string saddle. The strings were a 10-46 set so I subtract the diameter of the string to get 0.3700 – 0.046 = 0.324 inches to the bottom of the string. If I had replaced the strings with a 10-50 set, then I would add 0.050 inches to 0.324 to get 0.374 inches as the target height of saddle with strings.

Beware, making string height measurements this way elsewhere on the guitar, such as at the 12th fret, is more difficult because it takes little force to deflect the string and get an inaccurate caliper reading. This works at the saddle because it is difficult to press the string down directly adjacent to where it comes off the saddle.

Action

The most common measurement I am interested in on my guitar is the action at the 12th fret. This should be measured between the top of the fret and the bottom of the string. You need to make the measurement on both the 1st and 6th strings, but the rest of the strings are commonly adjusted in relation to the outer strings.

Although you could measure this the same way as I did for the saddle height, I don’t recommend the use of a calipers here because it takes a light touch to not depress the string slightly while taking the measurement. If you want to try this anyway, and think you can detect when the caliper just touches the string top without pushing it down, then I suggest you take the measurement to the fretboard, measure the fret height separately and calculate the action as fretboard-to-top of string minus string diameter minus fret height.

Although my eyes are not good enough to read ruler marks between frets and string, I can see a photo of this measurement just fine. In fact, even without taking the picture, the magnified image on my phone’s camera is enough for me to read the measurement.

As an alternative to using your phone’s camera, a magnifying glass with good lighting can help. I frequently see videos and pictures of Dan Erlewine and others for Stew-mac wearing magnifying visors. I purchased a less expensive model that is still useful for a variety of craft and hobby projects.

Whichever method you use, camera or your eyes, you should be careful about parallax. Your eyes or camera lens need to be looking straight on at the strings and ruler. If you are looking down at an angle, you will read a smaller value than exists. Pay attention to where the lens is located when making close-ups with your phone’s camera.

If your eyesight is good enough to read 1/64ths of an inch on a 6-inch ruler, it is probably easiest to take the measurements while holding your guitar in a playing position. The problem is generally having sufficient lighting to read the ruler marks. 

If you are going to take pictures with you phone, extra hands help. Practically, a tripod for your phone and the self-timer setting on the phone’s camera app make it easier to get a picture of the measurements. The guitar should be on a table or bench and it might help to tip it up at an angle with a pillow.

Pickup height

Measuring pickup heights using the caliper had the same problem as measuring action at the 12th fret. I have measured the heights of the pickups the same way I measure the action. 

Relief

If you need to measure relief to adjust your truss rod, feeler gauges are the most accurate method. If the feeler gauge can’t fit between the fret and the string without touching and moving the string, then the relief is less than the thickness of the feeler gauge. 

Many, including myself, adjust their relief to give a nearly flat neck. Long ago I read that you can check to make sure you have some non-zero relief, but not much, by tapping on the top of the string in the middle of the neck (which fret depends on which guitar you are setting up. Generally, you depress the strings at the first fret and the fret closest to where the neck joins the body to measure relief. The measurement is taken between these two positions. The key to tapping is you can hear the string click against the fret while feeling there wasn’t much movement.

Recommended Tools from Amazon

The following images are linked to Amazon product pages. I earn a commission from your purchases.

Steel rulers

Action gauge

Feeler gauges

Digital Calipers with selectable display for decimal inches, fractional inches, and millimeters.

Visor with LED lamp and interhanagable lenses.

Tripod and phone holder for taking pictures of measurments.