I just bought a 2003 US Strat with the 2 post trem and I want to start using 10's on the guitar. Will I have to widen the nut slots or are the nuts pre-cut for 9's and 10's? I was told once that .012 was the standard slot size for the high E slot, from the factory, is that true?
Thanks,
tfancil

I own a 08' Am. Dlx strat and changed from 9's to 10's without having to widen the nut slots. Did have to tinker with the trem and adjust the truss rod ever so slightly.

Back in 2003, the US Strats came stock with either 9s or 10s, I just can't remember which. Either way, chances are, you will NOT have to widen the nut slots.

Yes, 12s were the original gauge the nut was cut for but that ended decades ago.

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You dig?

I haven't measured the slots on either my US Standard or Deluxe, but I've set them both up for 10's in the past and neither one gave me any trouble at all after dialing them in. Same with my MIM FrankenStrat, and the handful of Squires that I've gone through. Never had any issues moving from 9's to 10's on any of them, or going back.

YMMV

WOW, Great responses! Thanks for the input guys I'm going to switch to 10's this weekend. I mostly play hardtails so having a trem is kind of new to me and I know that binding of the string at the nut can cause some tuning issues but I feel better about the switch now!
Thanks again,
tfancil

use pencil lead (graphite) as a dry lubricant where the friction occours to prevent any screachy trem noises....not necessary but it works if you need a fix.