TECHNOFRET 12th fret action gauge
We are now able to offer a most useful, and ultra-affordable, accessory for luthiers, guitar techs, and guitar players who like to do their own set-ups on their acoustic guitars.
Let me state straight away that to do accurate set-ups you will also require a couple of other inexpensive tools, namely a set of feeler gauges, and a digital caliper.
Both these items can be bought on Ebay for less than a fiver apiece.
Just search for "feeler gauges" and for "digital caliper"
The TECHNOFRET action gauge is a deceptively simple little gizmo, but, in conjunction with a digital caliper, will provide an extremely accurate reading of the height of the string above the fretboard at the 12th fret (or any other fret for that matter, but the 12th is the important one).
When you are fine-tuning your saddle to achieve optimum action, it is important to know what the target action height at the 12th fret should be. If you know what the target height is, and if you are able to measure the existing height accurately, then you know that if you remove twice the amount of the difference from the saddle, then your saddle height will be spot on, and you will have achieved your target 12th fret height.
If you are a devotee of internet guitar sites, you will probably have read posts from some poor deluded souls who recommend using a 6" rule and measuring the action in 64ths of an inch. Let me tell you, it is impossible to measure string height accurately using a steel rule. It can't be done. That is why we developed the TECHNOFRET action gauge.
The action gauge is a wedge shaped piece of white Corian, 3" long, 1/2" wide, and tapers in height from 1/4" down to zero.
In metric terms, it is 75mm long, 12.7mm wide, and tapers in height from 6.5 mm down to zero.
In use, you simply slip it between the fretboard and the string in front of the 12th fret until the gauge makes contact with both.
The way you tell when it makes contact is by continuously tapping on the string with your fingertip as you advance the gauge, the string will make a "pinging " sound until the moment when it makes contact, at which point it will cease to "ping". This point is very clearly defined.
At that point, use a sharp pencil to mark the gauge on either side of the string, remove the gauge and measure the thickness of the gauge in between the two pencil marks. This measurement is the exact distance between the fretboard and the underside of the string.
Once you have established the string height above the fretboard, you then need to ascertain the distance between the fret and the underside of the string, in order to find out what the action actually is.
This is accomplished by laying an accurate straight edge ( the TECHNOFRET fret rocker is the ideal tool for this) along the twelfth and thirteenth frets, and measuring the distance from the fretboard by inserting your feeler gauges until you have a nice snug fit. Once that is done, subtract your fret height from your string height and bingo! that is the action height. Simple.
The TECHNOFRET action gauge can be used for measuring the height of every string at every fret, all you need to do is lift up the adjacent strings by slipping a pencil underneath them. This is particularly useful for checking the height of the strings at the nut, when you need to lower the action by filing the slots. You get a ballpark figure very quickly, which you can then refine by using your feeler gauges, and then you can use the feeler gauges as a depth stop to tell you when you have filed deep enough.
All in all , a most useful accessory for any guitar tech, luthier or player.
You may think , hey, I could make this myself out of wood, and sure you could, but it wouldn't take long for the wood to get pitted by string contact, and to get grubby to the extent that you couldn't read the pencil marks. Corian is rock hard, will never wear out, and the pencil marks are both totally visible, and also easily and quickly removed with an eraser.
Just buy the TECHNOFRET action gauge, you know it makes sense ...
Additional info, dateline 14 August 2011: The gauge is proving useful in a surprising number of ways. Today I used it to cut a nut and a saddle out of a piece of solid bone. The gauge was used to measure and mark the width of the nut slot, and the bone blank (after being sanded flat on one side) was attached to a strip of MDF with double sided tape. The saw fence was then set by using the gauge to give just a hair of extra width, and the nut blank was cut. A couple of passes on the sanding block and the fit was perfect. Exactly the same process was used for the saddle. Quite a timesaver, no need for feeler gauges or calipers, no measuring involved, just working off a pencil mark.