Hey, so a simple question.
I have a older Cannondale frame that had a 1" threaded fork and headset, i discarded the fork but kept the headset just in case. I am looking at buying a 1" carbon Threadless fork for the frame and get a threadless headset as well but running into the problem of most 1" headsets ive seen or wanted (based of brand recognition or experience in the past) all have a 26.4 crown race, while the forks have a 27.0 crown race. Although the threaded carbon fork i am also considering has a 26.4 crown race and i can choose the length of steer tube (not fully threaded, only top 2").
My question is: could i get the threaded carbon fork (oversized steer tube for the frame), cut off the threaded portion, cut the steer tube to size for the frame and essentially use it as a threadless fork?
OR anyone have a suggestion of 1" headset with a 26.4 Crown Race that im not spending an arm and leg.

Quite a few crown races are interchangeable (and available on E-Bay). So, you may be able to use either a 26.4 or a 27.0 crown race with your headset.

Note that 1" threadless stems are relatively rare.

I don't see why you couldn't chop off the threaded part of the fork, as long as a star nut will fit and hold. However, depending on the frame size, you'll have to have a very long steer tube. The bottom of the threads should be about 2"or more beyond the length of your headtube.

Thanks for the response. I have a 1" 1/8 stem and carbon handle set up that I wanted to use with a Thompson 1" shim that'll allow using the stem I have, along with the 1" 1/8 spacers.
The threaded forks available come in sizes up to 300mm and the frame is 54cm so I'm assuming that the length is going to be plenty enough to chop down and have the ability to use as a Threadless. (Though I'll be measuring the length and stack heighth to make sure on the frame).
Thanks again for the response, just wanted a second opinion on the matter before I commit to the parts

The 27mm crown race seat on the fork is Japanese Industrial Standard (JIS). The 26.4mm crown race seat is ISO standard. Crown races come in both sizes and your headset vendor should have a 27mm JIS crown race that will work with your headset. You buy the headset which comes with 26.4mm crown race + the 27mm crown race and ditch the 26.4mm race which came with the headset.

Cane Creek customer service was very helpful, gave me the part number for their 27mm crown race compatible with 40 and 100 series headsets right over the phone. Call your vendor and ask them if they have a 27mm crown race for use with your headset.

An option is to have the fork milled from 27mm to 26.4mm so that it uses an ISO crown race. My experience is that few mechanics nowadays know how to do this and few will understand what you are trying to do when you ask. Park Tool makes the milling tool so don't let anyone tell you that you don't know what you are talking about. I could only find one guy in Atlanta willing to do it, a guy in his 60's who used to build frames.

Another option is to gently file the crown race seat. It takes some time but it can be done this way if you are mechanically inclined and very patient. I did this once, using a fine file to slowly remove metal and measuring frequently with a caliper. Eventually the 26.4mm crown race was able to be pressed on.

Thanks for the info, I'm a structural mechanic for the Air Force overseas and definitely have the time and patience to file it down to the 26.4 which easily sounds like a possibility. But will call the vendor prior to see what can be accomplished.

I'd keep the threaded fork and use a threadless stem adapter

No problem starting with a threaded fork and making it threadless by removing the threaded section. Just make sure the fork is long enough. As a guide, SOP id for forks to have 2" or 50mm of thread, so you'll need one at least that much much longer than you want to end up with. Also, don't forget that threadless forks need to be at least 2" longer than the threaded fork they replace, so you'll need a fork absolutely no less than 4-5" longer than your current fork, and more would be better.