How do you align watch hands? I can never get them to perfectly line up.

[GregG]

I am having trouble getting watch hands to line up when placing the hands back on the center pinion.  I usually wind down the mainspring, and then set the hands to noon when I place them back on the watch.  But no matter how close I get it, when I test out the synchronization by changing the time, the hour hand doesn't quite line up on the hour marker when the minute hand is at 12.  There is always some play in the gears between the canon pinion, the hour gear, and intermediate gear in between.  So as soon as I get the hands on the watch, the slop in the gears always throws it off immediately.  I can try to compensate for this by allowing the watch to be running when I place the hands on, meaning that the gears don't have any slop in them because they're being driven, but this is difficult too, as the time is changing as I'm trying to get the hands on at noon.

[rodabod]

For them while the watch is running if there is significant “slop”. It shouldn’t take too long with practice.  

[nickelsilver]

Do it with power on the train. Press the hour hand on, then set the watch forwards until it is perfectly aligned with 12. If you overshoot, go back a good 10 min+ and go forward again. Now set the minute hand at 12. This takes up the gear lash between the canon pinion, minute wheel, minute wheel pinion, and hour wheel in the direction that the watch will be pushing the gearing.

[oldhippy]

Always have a little power on this should take up any slack in the wheels. The only time you should have unnecessary movement between the hour and minute wheel would be wear to the teeth, although some movements don't have such good meshing between teeth as others, normally found in the cheaper movements. It's all down to practise when it comes to aline hands. If the alinement is poor put the hands on at 6 o'clock that way you will have as you call it slop will be even around the dial. 

[GregG]

Sorry for the late reply, but thank you everyone for the tips!