most of you have probably came across stewmac's fret rocker. there are some things about it I don't understand. I have several tools to check for high frets in the span of three frets, from machined rods, pieces of flexible straightedge and even a fret rocker analog laser cut to a thousand of a milimeter.
now my neck is straight as an arrow, the board and frets are both leveled, it was in a fact a refret. now I wanted to check for any high frets still remaining. let's imagine we have only 4 frets and we are first checking for high fret on no. 1, 2 and 3. if the thing rocks we know the no. 2 is high. but what if I rock on 2, 3 and 4 and it rocks too? then logically the third one is high too. how do I determine which of my frets are actually high and which aren't? if I file down no. 2 in the first scenario I would then in fact lower a fret even more so I'd enlarge the gap between 2, 3 and 4. this thing is so paradoxical to me, please help. :)
I don't have one of these but I still check fret height with some short machinist rulers. What you described sounds to me like 2 is the highest and 4 is the lowest. That is why you rock on 2 in the 1,2,3 test and rock on 3 in the 2,3,4 test. The first test pivots on 2 while the second test pivots on 3 because 4 is very low in comparison to all the others. In this case I would probably look to see of 4 was over driven or the others were not well seated.
The fret rocker is designed to "rock" back and forth when the middle of three frets is high, meaning taller not looking for a bag of Doritos.... So you have this part correct. And I also think that you understand from what you wrote that anything could be a fret rocker if it is milled absolutely flat and is the proper length to span three frets, hence the multi-sidedness (is that a word...?) of the fret rocker. Shorter sides are for closer frets and I think that you have this part down pat too.
Where you are making an assumption, and I am trying to be helpful here so please accept this as my attempt to be helpful and not critical... is that because your neck looks straight and the frets do too and you had a refret that it's likely that things are pretty straight. I would not make this assumption in so much as the different methods that manufacturers use including Plek machines and the differing methods for leveling things that different repair folks use always provides perfect results - this is not my experience.
The fret rocker is kind of sort of misleading in so much as it forces us to view several frets in isolation when in fact the fretboard, frets, and neck really need to be evaluated as a whole and as a system. The fret rocker will give you a quick visual and aural indication of a high fret, true, but dealing with this high fret in isolation is what troubles me....
Here's why - our strings are in fact straight edges to some degree when properly tensioned, etc. For decades repair folks, builders, f*ctory set-up people have used strings to check things such as relief. So a case can be made that our strings are ultimately the deciding factor on if something is going to interfere with them.
As such instead of relying on a fret rocker to determine where you might want to micro-manage fret height (again no offense intended, I actually speak like this too...) I like to view the fret rocker as a "fret knocker" with my value received from the thing being to do step one of any fret dress or need to evaluate a neck - checking for loose frets. Let's face it if fret two is high and you go about using one of a number of methods of milling fret two down if it comes to pass that fret two is "spongy" and loose and not in the looking for a hot date sense when you realize that fret two is loose and eventually correct this fret two will be milled too low and then you will have no choice but to have a fret dress and likely pay for it too.
As such I like to view the entire fretboard as a whole as mentioned. So I never mess with any individual frets adjusting their height as I think necessary. The board is milled into the shape that I desire which, by the way is not flat in so much as we have the ability to mill in fall-away and relief and also correct a board that has more relief on the treble side than the bass side. Once the board is milled into shape with sanding beams that are calibrated on a surface plate to be absolutely flat. Then we fret and if we shaped the board correctly and fretted consistently when we look for the shape that this individual guitar would benefit from installing the frets requires very little milling. Again the sanding beams are of various lengths so that one may concentrate in specific areas and this is at least to me a real art that took a long time to learn. The results though are frets and a board that compliments the inadequacies of the neck shape, it's tendencies under string tension, where the rod is effective and where it is not effective...., the player style, and a partridge in a pear tree.
So to me the fret rocker is a good parlor trick to show a client that a fret dress may be beneficial along with indications of wear, etc. But I would not bet my work day on using a fret rocker to do much beyond using it to gently tap every fret in three locations, both sides and the middle listening for the knocking noise to change and be slightly muted indicating a loose fret. Any hard object that fits the bill, and engineer's scale, etc can be used to tap each fret in three places looking for a loose fret.
A lot has been discussed on at least three builder forums about addressing high frets in isolation but for me I find this to be not unlike a long walk on a short pier because what really matter is what the strings, the straight edges that we discussed sees. Where the fret rocker may have some value is to use it on every combination of three frets directly under each and every string. How much time do you have? :) Because again you may not get an indication of a third fret being high under say the G string because you were rockin away under the high e and missed the high fret. This is yet another reason why how many folks use the fret rocker to check for high frets has inherent flaws in my humble opinion.
There is no substitute for checking for high frets (after all frets have been checked to make sure that they are not loose) beyond checking them all at once with an absolutely flat (and checked against a standard such as a calibrated surface plate) sanding beam. Bluing, magic marker, etc is placed on the fret tops (and no where else....) and then we observe where the beam hits, where it does not hit, the position of the truss rod is adjusted until we are hitting where we wish and then and only then will we know who's high, who's not, and then we can deal with them all as a "system" again as the strings see them too - as that system.
If it sounds complex it is and a really good fret dress is again an art that can take many fret dresses and experiences to learn. Sorry that there is no simple answer to your very good question and I freely admit that I don't have all the answers either but this is how I roll in terms of how I view frets - as a system, never in isolation.
thank you very much for your comprehensive reply it was really a joy to read. it is exactly what I was thinking. I understand frets as a system and isolating three frets just doesn't make sense. it's even easier to understand if all of our frets are perfectly in unison, flat as a pancake, and only one sticks out. lowering that fret in a fret rocker diagnosis fashion would mess up your perfect trueness spanning all along the fingerboard, because when you move to the next isolation group it will inherently become uneven too because you're always left with two frets from the previous group. in the end you're putting very good results into a fret butchery.
in my case if I rock the frets almost any group has a tiny amount of gap but you have to be very precise to dial it out. but when I lay any of my dozens of straightedges, from aluminium to steel rulers, some expensive and some cheap, I can't stick a .001'' feeler gauge under any of them on any of the fret except for the fallaway area which of course makes sense. up until now I was checking my frets with straightedges and sighting down the way against a good light and I was always getting a nice uniform beam of shining light with no frets shadowing or shinning out. I just always strive to surgical precision that's why I wanted to give fret rocker a go.
I think it's very rude to play a fret rocker trick on a customer. if I was that customer I'd like to see that fret rocker or whatever you use sitting flat and rigid after the so-called fret doctor finishes the job. but most of the people are just happy to meet someone being so in-depth with the job, no matter if they do an inferior job in the end. most people become believers once a 'fact' is projected on them. but this is not me, I wanna make honest money
You are very welcome and it's very clear to me that you "get-it" from your reply and also see our frets, neck, board, etc. as the strings see it - as a system.
Don't get me wrong though the fret rocker can also confirm a high fret but this is not necessary in deciding where to concentrate on the frets during a fret dress because ultimately the precision sanding beam and the bluing will tell you all of this, for every fret in every location all at once.
When I discuss a recommendation for a fret dress with my customers I need to have other reasons for the recommendation before offering one. Typical other reasons such as excess fret wear, client complaints of "fretting out", inability to lower the action to a "realistic...." and/or desired level, and of course experience where with some guitars certain characteristics that we see over and over may lead to idea of a fret dress being beneficial. Fender electrics with the bolt on neck where the rod does not impact the area over the body and the design of the bolt-on itself often lead to a "ski-ramp" of the over the body frets where the fretboard actually kicks upward. We see this when placing the precision leveling beam over the entire neck and with bluing getting a read of which frets are high. The extension area over the body often imprints first preventing any other frets except the first 3 or so from imprinting. This is where milling in fall-away and getting the extension frets out of the way permits the beam to register on most of the frets with truss rod manipulation.
A really good set-up requires that our fret work be in order or the action, if desired, will be limited by factors such as a kicked-up extension or any other high frets.
What helped put all of this in perspective for me was to attempt to take one's view of the fretboard as our strings see it, for better or worse, high AND low frets and all.... This is why I won't do partial fret dresses or even deal with a high fret in isolation unless there is a very good and limiting reason to do so. Often one is addressing a symptom of a greater need to have the frets completely dressed and not individual frets in isolation.
When using a precession sanding beam that has been milled and checked on a calibrated surface plate we estimate that our tolerances are in the neighborhood .0005" which as you can imagine is pretty tight. Attacking individual frets in specific areas is not likely to provide tolerances this tight and as indicated may also be creating new limiting factors when a complete fret dress is eventually done because the frets were not viewed as the system that they are.
Tadej - there's one other point which hasn't been mentioned. Maybe it's obvious, but it wasn't for me when I started, so I'll say it anyway. A perfectly straight neck, with zero relief and no string tension, may no longer be perfectly straight once you string it up and dial out the relief on the trussrod. You need to get to that point before you really know which frets (if any) need work. Like Hesh says, you need to look at the whole system, and that includes the influence of the strings themselves.
I would take Hesh's advice I never try and dress one fret or two as in most cases you will end up with the next fet to it low.I don't owen a fret rocker. Besids going up the fret board useing the strings they will tell you what fret is not right. When I have a customer bring a Guitar in with fret problems I jut tell them it needs a fret dress...........Bill..
Like everybody else. I don't dress individual frets. When I rock frets, it's usually looking for low spots so I can have some idea how much I will need to remove overall. I've been saved a time or two by finding a very low fret that was going to force me to take too much off of other frets to even up the lowest. In the end, I always dress all of the frets, not just the high ones.
I SUPORT THE GUITAR AT BOTH ENDS CUT OFF THE STRINGS AND LIKE mARTIN GUITAR DOSE I WEIGHT THE GUITAR WITH 15 LB OR LEAD AROUNE THE OR INSIDE THE HOLE THEN Mark all the fret tops with a blue felt marker then adjust the truss rod to level as can be gotten with a flexible 16 inch ruler than with a full length flat thing with sticket sandpaper sand the full length of the fingerboard and keep looking at the frets at the blue markers and sand until all fret tops have a shinny spot in the blue marker. You can add relief if needed by loosen the truss rod.
I set the guitar up exactly the way I want it and then I play it. If a fret buzzes or chokes I mark under that string with felt marker. Then I know how to dress the frets. The fret rocker doesn't work for me I find myself fixing things that aren't broken.