Can we assume that you mean these things?
https://www.amazon.co.uk/Leen4You-Ferrocerium-Drilled-Survival-Starter/dp/B07DNNY1BR
Pack of 5, £3.99
Length: 26mm(1"), Diameter:8mm(0.31"),Diameter of the Drilled Hole: 4mm(0.16")
If that is right, I think you have gone to a lot of trouble so as to feel that you have not wasted £4...probably more effort than it was worth I am afraid.
Ferro rod toggles on a key chain is not the best idea just due to the nature of the material and how it is used. These toggle things are not bushcraft, they are toys to snare the unwary gear enthusiast. Don't feel too bad, we all buy stuff like that at some point!
Some things worth knowing about ferro rods.
They are not all the same! The alloy mix varies from brand to brand and supplier to supplier. This does not mean that some that are harder to strike sparks from are inferior than the ones easier to strike sparks from, this material is used for things other than lighting camp fires and harder, more resistant alloy mixes can be better in those industrial type applications. Some of these harder to strike rods can be bough in bulk quite cheaply. They tend to be more corrosion resistant. Unless you are buying a well known brand you are unlikely to know what it is that you are getting. The good ones tend to cost more.
Rods that are easy to spark will corrode very readily in the presence of moisture. Hell, they will corrode while sat in a wooden drawer in you house without ever going outside. When they corrode they leave grey powder behind that is hard to get out of pocket linings! Guess how I found out...
Even if they don't corrode, they will wear with contact with the keys and leave residue behind as a result.
You must have a hard and sharp edge to scrape sparks off even the easy rods. The soft steel in keys isn't enough, and Swiss Army are known for being a bit soft (54HRC). A small piece of broken and ground file is more like the right stuff. Maybe grinding off the flutes of a drill bit and putting an edge on the end would work too.
You need to be able to both support the rod and bear down on the scraper, which is hard if the scraper is very small or hard to hold. I would imagine that such small rods could only be used with any effect by pinning one end against a hard surface at about 20deg off vertical and have the tinder held to the scraper itself as it is run down the rod. As you say, dang tricky.
It is very rare that I really need to make fire with what is in my pocket, but when I do, it tends to be situations where I want flame, rather than a spark that needs coaxing. So, I carry a Peanut lighter on my key ring. I have a cheap one whose case is clearly not made of stainless steel, but even so, it has been good and handy for several years now. Another option, if you really like sparks, is the Exotac Nano, it is bigger than you probably want, and more expensive, but it is fully waterproof and had a very good striker built in.
Best of luck
Chris