So you have or are building a 4x2 (tuner orientation) headstock guitar and you want to buy or upgrade your tuners? Great! Only...who sells good 4x2 tuners?
The solution, if you like Sperzels, is to buy either a 6 in-line or 3x3 set and reverse the orientation of one or more tuners.
I am going for a more compact 4x2 headstock for a neck-through extended scale 6-string electric guitar I'm building myself (from scratch!), so I opted for the 6 in-line option vs. the 3x3 option to start as the tuner buttons are smaller. Either will work, however. The set shown here is the Sperzel Trim-Lok in matte black - I'm not usually one for black hardware but I'm going this way on this guitar and these are very slick looking.
As I purchased a 6 in-line set of Sperzels they have staggered shafts (long, medium, short), the idea being that if you have a flat headstock (e.g. Strat, Ernie Ball Music Man, etc.) as opposed to a slanted headstock (e.g. Les Paul, PRS, etc) you can get a high enough string break angle over the nut to avoid needed a string tree. To do this on a normal 6 in-line headstock you want the smallest shafts to be the farthest away from the headstock (the high E and B strings on a traditional vs. reverse headstock).
I chose to reverse one of the small ones (for the E string) and one of the medium ones (for the B string), so from low to high E on my 4x2 headstock I'll have: long, long, medium, short, medium short).
Personally I found the difference between the short and medium shafts to be slight, and I was only able to see which was which by comparing the two shafts side-by-side in the manner illustrated below:
As I like the black finish on these and I know right beneath that finish is shiny metal I'm taking extra precautions as to not mar the finish. Here I have taken a small bit of electrical tape and covered the end of the flathead screwdriver I'm using. (I have a set of Wiha screwdrivers and I love them - they are a cut above anything I've used before). The way I look at it is little steps like this add up and go a long way to a great looking end product - just do it!
Take your screwdriver and gently unscrew the screw holding in the tuner button assembly.
Ease out the tuner button screw and lay out the parts in the order the came out. From right to left we have the screw, the locking nut (on the screw in this picture - don't lose it!), the tuner button, the plastic washer, a plastic collar, and the tuner gearbox/shaft.
Now we are going to remove the shaft. Push gently on the shaft, in this pic I pushed the shaft to the left, and gently rotate counterclockwise as needed. Do not force the shaft out - it will come out easy when you push just right.
You'll wind up with a lubricated shaft that looks like this. Do not wipe off any of the lubricant from this assembly or the gearbox - you can always clean it up after you are done, but the lubricant is important to the longevity and performance of your tuners.
There isn't a picture of this next step, but take the shaft and insert it into the gearbox going the opposite direction. As with the above steps do not force anything - it should go in easy. If it helps gently rotate the shaft until it is fully seated in the gearbox.
Now you are ready for reassembly. Even though the post is still pointing to the "right" as it was in the fifth photo, you can tell it has been reversed as the gearbox is now on "top" vs. in the original photo the gearbox as on the "bottom". Put the collar on the shaft, then the washer, then the button (mine actually fit into a slot on the shaft, so rotate around to find the detent as needed) and then the screw. As a good trick to make sure you don't ruin the screw/shaft by accidentally cross-threading the screw, turn the screw counter-clockwise until you feel it "click". Now you are right at the beginnging of the threads in the female part with the threads of your male part. Now turn the screw clockwise lightly and you shouldn't cross thread. The screw should go in easy though, so if it doesn't, stop, back it out, and try again - don't force it! You could strip the screwhead or the screw threads. If you overtighten this screw you will find the tuner button difficult to turn. I screwed it in relatively lightly (not even as hard as a handshake).
The reversed tuner with the screw most of the way in.
Do the same thing for another one and there you have it - a 4x2 tuner set!
In case any of the above was confusing, or you prefer videos, please see the Sperzel video below showing Roger, one of Sperzel's techs, doing this exact same thing: