I would like to file down (just a bit) a metal tube's end to make it completely flat. See a drawing of it in another question of mine on this site Fix a faucet that has a groove . Taking that drawing as the case, I would like to file it from what in the drawing is the top, in order for that top to be flat instead of having that groove. In reality the groove is very small, but it's big enough to cause a bit of a drip to pass through it despite a rubber part closing it from the top.
I was thinking that if there is some revolving small flat file for a drill, something like the following drawing (the flat black part being reminiscent of sandpaper):
I could point the drill towards the tube and file the edge so that there will be no groove and the rubber part will close it hermetically. I can't get to the tube's edge from the side because it's surrounded by another tube which goes farther than its edge. But I can get to it from the top.
I remember seeing something like what I'm looking for but much bigger (and perhaps for wood) and I can't find any images of it now. I'm probably using the wrong keywords.
So does such a file exist, and if so, what is it called?
EDIT
Perhaps the rubber part that closes on the pipe is called a compression faucet valve cartridge.
I can't cut it off from the side. Unfortunately there is absolutely no access from the side.
As mentioned in a comment, the term seems to be a sanding disc. But at least so far, I can't find any narrow ones with a diameter of under an inch. Do those exist? I just remembered where I've seen them – at the dentist. Though I assume dentists' tools would be super expensive. I just need an attachment for a drill.
EDIT 2
Here's the best I could do (a cross section of what I have):
The dotted yellow line is what I need to file. Its diameter is a little under half an inch (around 1 cm). The green is the rubber part that's supposed to seal it.
Best Answer
It sounds like what you are describing here (and in the other thread) is called the "seat" for the valve stem washer, and usually that seat is replaceable for this exact reason. If it is replaceable, the inside will have a geometric shape, usually hexagonal, sometimes square (or the corners of a square cut into the sides of a round opening, see below), to accept a tool that us used to unscrew and remove it. Here is an example of a bad faucet seat, one with a "groove" in it like you describe.
You typically cannot see anything but the end when you remove the valve stem, so you may not have known that this is a separate piece. But if you look on this photo, the insides are hexagonal, so you can use a hex key tool to remove it. They are almost always made of brass so that they do not corrode and become impossible to remove, but it sometimes takes some effort. Once you do so, take it to a hardware store and you can buy new seats, they are cheap. They will come in pairs, replace them both because if one is corroded, the other one probably is not far from it too.
Here is an example of the type that needs a square tool.