So I am getting some spiked acorn nuts for a hayabusa I am getting in the mail and they have two options, coarse threads and fine, witch one should I buy?
I would suggest the coarse thread option. I am not 100% sure how these are used on a hayabusa since I am new to yoyo stuff and I am pretty sure that you know that the coarse thread nut only matches a coarse thread screw.
But from the engineering background here is when to use coarse vs fine
Always use coarse threads by default, unless you have a reason to use fine thread.
Typically cheaper and more commonly availible.
Easier to install.
Less likely to cross thread or have damages threads.
Much easier to hand thread a hole for a coarse thread.
They are slightly highter clamping load and tensile strength. (About 10 to 15%)
They allow for a finer degree of control if you are using them for adjustments.
They are more resistant to vibrating loose.
Additionally, if you are working with thin material a fine thread will allow you to get more threads engaged. Typically, the minimum thread engagement is 3 full threads. A lot of people also use the diameter of the screw as a guide. So if your screw is .25" in diameter it should have .25" of thread engagement.
Based on all of that stuff, I would say you don’t need the clamping strength or the fine adjustment. The vibration benefit is tiny, and out weighed by the cross-threading risk of fine thread.
Just my opinion.
To follow up on what jupdyke said, the Hyabusa uses a course thread M4 bolt and nut axle. Since you are using spiked acorn nuts, I would suggest getting those in the same specification as the stock axle and then using a setscrew to thread between them and act as the new axle.
The acorn nuts are the same specifications in width but it does not say anything about the threads per inch. I think i will go for it! Thanks Jupdyke and Mrcnja!