That depends. If you are using just one side to face the edge of a workpiece, then four flutes doubles the number of "teeth", so the feed per tooth can be doubled for a given RPM and workpiece material/cutter material combination.
O.K. And as someone else mentioned, are you locking the axis which you don't want to move? Vibration can cause the handwheel to rotate, especially if it is not a balanced handwheel (extra mass on the side opposite the crank handle, so it will balance in any position).
Hmm ... I would use something like Rigid's high sulfur threading oil in preference to that for that particular task.
And an alternative possibility is simply a jet of compressed air directed right at the cut to blow chips clear so they can't build up on the cutter and bind it in the cut.
O.K. With a 1/4" end mill, your top speed puts you at 71.99 SFM, which is probably not bad with a mild steel and a *good* HSS milling cutter.
Yes -- when your RPM is an unknown, yes, you don't know what you have even if you know your IPM (inches per minute) based on how fast you are cranking the leadscrew. (Of course, in the machines where it really matters, the spindle is geared to the table feed, so it is truly a feed per tooth, even if the spindle loads down a bit -- so does the feed.) And in CNC, it is computer determined.
And with key stock, it is more the gummyness of the steel, not the hardness. I believe that key stock is low enough carbon so you can't harden it.
But yes -- if you had hardened steel, the speeds have to be reduced.
And the shaking could cause the other axis to feed if it is not locked. Does your machine have locks for each axis?
:-) Read the posting by Teenut (archived somewhere that someone will surely point out) discussing how a real machinist sets the feed on a machine in production. (The basic idea is to start cranking until you feel uncomfortable about the machine's behavior, back off a little, and then bring the power feed up until you feel it catch up with your cranking. :-)
For slot milling, at least. For a lot of other things, four flutes is a better choice. Slots are a special case.
Good Luck, DoN.