It will not make your token a non-security if you use your own exchange to allow people to convert it to fiat.

The crucial part is if you, the operator, are profiting from the cryptocurrency (e.g. through premined tokens/units), and if the value of this currency depends on your own efforts.

One way to make a SEC compliant cryptocurrency is distributing them in a totally decentralized way, e.g. via Proof-of-work, but all tokens have to be distributed that way, even 1% premine can make it a security. Another way is to use it as an utility token which cannot grow in value, i.e. offering your own services for this crypto, but at a fixed rate, so it passes the Howey test.