I'm sure this will likely end up being one of those, "how long is a piece of string?" questions, but here we go. . .
I have one of the auction site Chinese bench/desktop CNC engravers. (The 3040 T/D 3 Axis machine with the black box controller)

The machine has been surprisingly reliable for me. Lately I've had a few issues with some nuisance false limit switch triggers. I'm 90% sure it was a combination of a loose crimp connector and running my limit switch wiring too close to stepper motor cables. I fixed that but decided now is as good of a time as any to correct other issues. (The limit switch wiring I did a few years back in a hurry should be redone anyway.)

I'm working my way through properly grounding the machine, and rewiring my limit switches. I plan on soldering and using double shielded wire with a properly grounded drain wire. That's all easy enough (after some research and reading of course).

The rest of the machine is more of a problem. As is common with most of these cheap machines, nothing is shielded from the factory. Instead of the downtime and expense associated with rewiring everything with shielded cable, I'd like to use some ferrite clamps. The problem is, there are many different materials and choices depending on the frequency of noise you're trying to keep out.

Or. . . you can just search "Ferrite" and get the cheap packs of a dozen or so ferrites with no sort of ratings etc. on them. I know most/alot of people just order "Ferrites" and use whatever arrives. Is there a better way to approach things? Which sort of EMI/EMC/RFI electronic noise frequency ranges affect these CNC machines the most? Is there a "one size fits all" or "best ferrite" to use? Is it all just a waste of time?

I'm sure the right answer is "it depends." While the machine is running I occasionally use some 2.5ghz or 5 ghz WiFi and Bluetooth from time to time in the shop. It's easy enough to NOT do that if they cause issues. Other than that I may have the 110V air compressor going, or a shop vac running for dust control. I may use a miter saw, sander or other corded or cordless powertool. Pretty sure the neighbor behind the shop has a ham radio setup, but I'm not sure how often he actually messes with it. I imagine all of these could affect things.

I use this machine mainly for large rough cutting of pockets into wood. These are short runs of probably 10 to 20 minutes. I really haven't had many problems. However, I'm looking to do a bit more precise and intricate stuff that will take longer runs. I'd also like to start engraving some aluminum, brass and acrylic from time to time. I figured eliminating the EMI issues as best as possible is a good idea.

Any help or insight is greatly appreciated!