1: Indicates an absolute quantitative limit with the connotation that the amount is small: only, just."
Kinō kurasu ni kita gakusei wa, gonin dake deshita.
Only five students came to class yesterday.
Kyō wa ichi-jikan dake terebi o mimashita.
Today I watched TV for only an hour.
2: Indicates an extent or amount "as...as."
Dōzo osuki na dake onomi kudasai.
Please drink as much as you wish.
Dekiru dake hayaku ikimasu.
I'll go 「be on my way, leave, get there」as soon as I can.
「Lit., To the extent that I can, I will go quickly.」
3: The phrases dake ni, dake atte, and dake no koto wa aru, indicate the cause or precondition for a certain result or state of affairs (when the result meets expectations, does not meet expectations, or is considered a natural outcome).
A) When the result meets expectations and is therefore worth the effort of achieving: "...was worthwhile."
Ano daigaku ni gōkaku dekita kara, benkyō shita dake no koto wa atta.
I passed [the entrance examination to] that university, so the studying I did was worth it.
Terada-san wa watashi no purezento o yorokonde kureta no de, muri shite katta dake no koto wa atta.
Since Terada was happy [pleased] with my present, it was worth all the trouble I went to in buying it.
B) When the result does not meet expectations and is therefore discouraging: "given the fact that."
Kare wa kanojo ni muchū datta dake ni, shitsuren no shokku wa totemo ōkikatta.
Given the fact that he was head over heels in love, losing her was a big blow.
Isshō-kenmei ni benkyō shita dake ni, fu-gōkaku no tsūchi o uketotta toki, Yamamoto-san wa hijō ni gakkari shita.
Since he had studied so hard, Yamamoto was extremely disappointed when he received notification that he had failed.
「Given the fact that he had studied so hard, Yamamoto was crushed when he learned that he had not been accepted.」
C) When the outcome is seen as a natural result of foregoing conditions: "as you might expect."
Satō-san wa Igirisu no daigaku de benkyō shita dake atte, eigo ga umaidesu ne.
As you might expect from his having studied at a university in England, Sato's English is quite good.
Koko wa hokkaidō dake ni, samusa ga kibishī desu.
As you might expect from this being Hokkaido, it is terribly cold.
「It is terribly cold here in Hokkaido, as you might expect.」
4. "Not only...but also"
NOTE: While bakari may replace dake in this usage, it is slightly more emphatic.
Harada-san wa piano dake de naku, uta mo umai-n desu yo.
Harada is good not only at the piano, but also at singing.
Eigo dake denaku furansu-go mo benkyō shitai-n desu.
I want to study not only English, but French as well.
Hope this helps, and see you again！
°˖ ✧◝(○ ヮ ○)◜✧˖ ° こゆうきあいはら °˖ ✧◝(○ ヮ ○)◜✧˖ °