approximately is the key word here...
The "recommendation" is just that, a recommended starting point. You can take 5 printers of the exact same model, and no two will be exactly the same when they are dialed in to their optimum performance.

+1v

I have 3 SD2s and two units had the same boards. Sangs and RUMBAs. Each time they were dialed different. The only time I check the voltages is if I think the driver died or some crazy thing like that. I always tune by ear, then by performance for fine tuning.

Just get it in the ballpark then spend 20mins or so tweaking it.

So does anyone know why solidoodle would recommends approximately 1V?

approximately is the key word here...
The "recommendation" is just that, a recommended starting point. You can take 5 printers of the exact same model, and no two will be exactly the same when they are dialed in to their optimum performance.

Well... If people are brave enough to probe for voltage, they are more then likely, able to follow a couple of additional instructions.
I've more than halved the voltage(Somewhere in the .400-.600v range), and trying a test print.

Just sayin, some people are not and in fact some expect these to be plug and play like a paper printer and are stupefied when they find out they have to do maintenance, tweaks, and even mods as a common thing.

So does anyone know why solidoodle would recommends approximately 1V?

It's a ballpark number and will most likely work for those not versed in or brave enough to adjust it...

It really does depend on the board, the stepper drivers, and the motors... What works on one setup will more than likely be way off for another.

for my #2 SD4 with the stock Rev E Printrboard it is in the 1.0v range for X, Y, & Z - but they are tuned by ear/feel from that point to work as efficiently as possible without skipping, or overheating.
#1 SD4 is running a Rumba and thus is VERY different...
the 2 Folgertech kits (Prusa & Kossel) both run Ramps with 4988 stepper drivers, and yet are both just a bit different from each other because of how they operate.

+1, that's what I'm talking about.

for my #2 SD4 with the stock Rev E Printrboard it is in the 1.0v range for X, Y, & Z - but they are tuned by ear/feel from that point to work as efficiently as possible without skipping, or overheating.
#1 SD4 is running a Rumba and thus is VERY different...
the 2 Folgertech kits (Prusa & Kossel) both run Ramps with 4988 stepper drivers, and yet are both just a bit different from each other because of how they operate.

If you've increased Vref to max and tried to run motors, it is possible you have overheated your stepper IC's and killed them. This is unfortunate. Was there a reason to adjust the Vref initially? Was this tuning the printer up, or was there a fault already?

The typical Vref will be different depending on your board and motors, and can be worked out easily enough given enough information. More information than we currently have. Please disregard the large collection of values you've already been provided with (.3-.6V, 1V, .350V-.500V, 0.17V, 0.250V, 0.400V at current count... Any one of those could be right or even more likely wrong. GUYS, THIS IS CONFUSING!!).

Similarly as wardjr and carl suggest, I'm a fan of adjusting by ear too - the Vref = x.xxV thing really is just a starting point, often near enough is good enough. I doesn't take into consideration variation in motors and the mechanical system. Try that when you've got it working again.

all of my pots are at 1v except e which is at .250v  or pretty damn close.

Running your motors at that current will burn them out earlier than they should.

The extruder requires the most torque so it should be the highest of all of them. Then your axis drivers should be about half of your extruder.

My axis drivers are at .250 and my extruder is at .400 and they run very quite and just barely warm to the touch even after 12 hours of printing.

1 volt means you are feeding your motor 1 amp of current and they will use it and push themselves much harder then they need to.

I adjust mine down to the point where they just buzz and not move. I then go up .025 volts. Run them and see if they move the full axis. If they do fine, if they stall then I go up another .025 until they can move the full axis with no stalls. Then I do a print to make sure they don't stall or skip steps. That usually makes me go up one more .025 and that is where they stay.