Removable Studs (is it a thing?)
 

Where I live, winter is hit or miss. I would hate to get a fatbike and have winters with very little snow and this good conditions for a fatbike. I was wondering if there are tires where you can screw in the studs for winter, and remove them in the spring for occasional trail rides, then back in the winter...

I haven't heard of any socketed studs on a bike tire, or car tire. Is there such a thing on a car tire? I'd imagine there would be a large weight penalty for sockets plus studs on a bike tire. I know you can certainly remove studs on a bike tire and replace them. Removing them, then riding, then re-installing would require thoroughly cleaning out each stud seat in the tire before re-installing the stud. I ride studs in the winter here on a regular non-fat MTN bike.

Having manually installed a complete set of studs in a pair of tires, I can say that it's a tedious process. I would much prefer to have two sets of tires, one with studs, and one without. The time savings would be well worth the cost of extra tires.

To answer your question, studs for bicycle tires do not screw in: they have a flange that fits into sort of a t-shaped socket. The tool used to insert them should also be able to remove them, but it requires some effort to overcome the forces of the rubber that hold the studs in place in the pockets.

I just tried removing a stud from a 45NRTH Dillinger 5 using the 45NRTH stud insertion tool, and it came out easily enough, simply prying it to the side. I'd hate to do it 516 times, though.

There are Grip Studs that can be added to non-studded tires. They are pricey and a bunch of work. If you are just cruising around, they are good on ice.
https://gripstuds.com

You can re-install studs .. but once dirt is in the stud pockets, they may not stay in well. Besides, it would be a pain to do.

I only install studs in new and clean tires. At 216 studs per tire, that is all I ever want to do.

I just have 2 sets of tires I swap seasonally. If you have money, a separate winter wheel set is even better.

I don't know of tires that have quick/easy studs to add/remove. I ride Dillinger studded tires for winter, and in Minnesota, we have many months of studded tire conditions every year. So I have summer and winter tires for my Pugsley. The only reason for studded tires is ice, if your winters don't include weeks (or months) of icy trails/roads, I'd recommend a good snow tire (Dillinger w/o studs or Jumbo Jim).

Here's a video clip I made replacing worn studs on Dillinger 4 tires (you can see this would take a long time for two tires):