If you mean does it have to be chopped to build a mine, the answer is yes.
If you mean should you first spend 3 turns chopping and then 4 turns building a mine instead of 7 turns building a mine and getting the forest chopped at the end, the answer is still yes, almost all the time. You get the hammers from the chop earlier, which means you probably complete the build earlier and get the benefits from that build earlier.
The exceptions are if you have Mathematics coming in in 4-6 turns (wait with the chop for 50% extra hammers), or if you want the hammers to go into something you cannot build until 4-6 turns from now. For example a wonder that you don't have the tech for yet, but resource boost on the chop hammers. Sometimes you also want to delay the chop for other micro reasons. If you for example are chopping many forests into cheap early units, you want to time them so that you don't get too much overflow, which would be turned into gold instead of hammers.
You can time the chop to any turn between 3-7 turns from starting chopping/mining. For example, you can do 2 turns of chopping, then 2 turns of building mine, then again one turn of chopping to finish the chop, then 2 more turns of building mine to finish the mine.