One of my saddle lock screws in my JS 1200 is broken, and I was wondering if it was possibly to change it with another regular screw with the same size? Any chance of harming the guitar?
The screw threads might be different. I'd contact Rich at Ibanez Rules and just order a replacement part.
My name is Tom, feel free to use it.
Do you mean the string lock screw, or the saddle (intonation) screw?
If its the intonation screw, I'd replace it with a more durable one (I got some stainless steel ones off ebay) because the original Ibanez ones are very soft.

If its the string lock screw, you can get them from IbanezRules. I doubt you'd be able to find another screw with a thread that would fit the saddles.
It's the ones you take out to adjust intonation. Ill just try with some similar sized screws before I try ordering any replacement parts.