You need to install the Bitcoin core wallet: https://bitcoin.org/en/download
Once the wallet downloads all blockchain files, you can find them under /Users/yourusername/AppData/Roaming/Bitcoin/blocks/
I use the BitcoinJ library in Java to parse the blockchain and extract chainlets.
See the Parser.java to start extracting chainlets. Send me an email at cuneyt.akcora AT umanitoba dot ca if you just want to receive the latest chainlets from me in a file.