Is there a difference in usage between yarım and buçuk?

Buçuk is used for time only i think.

I think that buçuk is used to tell the time/hour, like "saat on buçuk" (the time is ten and a half).

As for the pub...make those beers two! I m on my way!

"Buçuk" is used after a cardinal number. "Yarım" is used on its own.

iki buçuk saat sonra : two and a half hours later
yarım saat sonra : half hours later

If there is cardinal number (tam sayı preceeding we use buçuk. If there isn't, we use yarım.

Yes, but both examples had to do with time/hour. Does this mean that buçuk is really used only to explain time?

I mean you can't use buçuk to say iki buçuk portakal, can you? When you wanna say "half of something" you use yarım (yarım portakal), right?

No, buçuk can be used for anything as long as there is a preceeding cardinal number.

For instance this would be a normal and common sentence to say:

" Bir buçuk porsiyon döner istiyorum. "

Here is another example:

" iki buçuk bardak su "

Hmm I see. Thank you Erdinc.

(If I ever catch my teacher.. )

And also..

1,5 >> This is "bir buçuk" (You can NOT say "bir yarım")
1/2 or 0,5 >> This is "yarım"

For time;

01:30 >> Bir buçuk
04:30 >> Dört buçuk
12:30(p.m.) or 00:30(a.m.) >> yarım ( or on iki buçuk)

Yes, you got it right.

Yarım ekmek, bir ekmek, bir buçuk ekmek, iki ekmek, iki buçuk ekmek, ...

edit:
"dört yarım yumurta" is alright. This is four times half = 4 x 1/2
While "dört buçuk" is found and a half = 4 + 1/2