Filing piston rings

What's the best way to file the rings to achieve some gap David

A small fine file, held as square as you can discern by eye.

Hold the ring in your fingers, very near to the end you are filing. Avoid twisting the ring.

There is benefit in making the gap in the second ring 30% bigger than the top ring gap.

fireflake said:

What's the best way to file the rings to achieve some gap David

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The easiest way to avoid drama is to use a dedicated piston ring filing tool, around $100.
You still need to deburr the edges with a suitable fine hand stone (lapping carefully)

Personally I prefer to use a Dremel with a micro grinding disc

I use a strip of sandpaper folded over so there is grit on both sides and clamp it in a vice. That is about as narrow a file as you can get. Then I mark the back of the ring with a felt pen 180 degrees away from the gap and align it with the vice jaws so, as I am drawing the ring towards myself I can keep it straight, no wiggle while I am filing.
I found the ring gapping tool mentioned above creates a gap that is not square when the ring is compressed.

seattle##gs said:

I found the ring gapping tool mentioned above creates a gap that is not square when the ring is compressed.

Click to expand...

That probably doesn’t matter much, but it does make you wonder where the $100 value lies.

Is there a necessity for the gap to be perfectly square? I thought the gap was just to ensure the rings ends don’t touch when expanded by heat. Near enough to square and gap checked with feeler gauge does me. All rings I’ve used are quite easy to file by hand with a points file, I think it would be too easy to remove to much material with a dremel.