So I am looking to buy a new front fork for a bike I am putting together. I've taken some measurements of the head tube on the frame, it's 185mm long and fits a 1 1/8" headset. So obviously I have to take those into account when I am purchasing.

My question is basically between the two types of forks which I understand are either threaded or threadless. Are these two types largely frame dependent, what I mean by that is does the frame of the bike determine which type of fork you will have to purchase or are they interchangeable so long as the headset is the right size to fit the head tube? The specs on the manufacturer website aren't clear on this matter and I cannot tell just by looking because I lack the required expertise, and while a google search reveals a lot of info on both types of forks I cannot seem to find anything on whether the two are interchangeable for frames if they fit the measurements.

The frame is a Nashbar Double-Butted Aluminium road frame #NB-RDBAF if that helps.

Threadless or threaded depends only on the fork, not on the frame. If you buy a threadless fork for your frame, you will also need a threadless headset and stem.

Threadless forks come with an longer steerer tube than almost any frame requires and you cut it to the desired length after you choose the headset, stem and any spacers you want to have the handlebars positioned to your liking.

BTW, threadless has become the de facto standard for newer bikes and threaded steerers and headsets are getting to be rare.

Alright, I suspected that was the case but was not absolutely sure. Yeah, I noticed in my searches that threaded radically cut down the amount of forks I could look at. Good to know, you have my thanks.