Personally, I don't think we can say that there is a standard dimension as far as where the sink is supposed to start. Most sinks have a 3/4" to 1 1/4" lip, that is 1/2" that can create an issue.
First check the PHYSICAL sink, measure the lip, then do the following to get as close as possible to the edge:
1 1/2" + (standard Edge Detail)
3/4" + (Faceframe of cabinet)
? ?/?" (lip of sink)
The total will give you your overall dimension, it could vary from 3" to 4 1/2" depending on your edge detail, sink lip, etc. I've done some at 5" even 7".
Don't forget to check for clearance for the faucets, mostly if you have a backsplash, but also check for the plumbing, sometimes the lip on the sink is big and you must core the faucet hole back a bit.
Also if you want a reveal or overhang on the edge of the sink, don't forget to add or subtract the reveal(-?) or overhang(+?). Most reveals and/or overhangs are about 1/4" but I left the ? for you to decide.
As a rule of thumb if the sink is small enough to push it back a good 1/4", it will be much better than damaging your cabinet faceframe to make the sink fit.
Hope I didn't get too technical. ; ) This is an exercise that your fabricator should do for you, and you should just approve according to your opinion, not your technical abilities, but it never hurts to have an idea what is supposed to be done.
Vic
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