Files get clogged and stop working. You need to use a file card on your file after sharpening your saw (or anything else). As far as testing, paint the metal with sharpy and then file it. If the sharpy mark is gone, then the file is still sharp. But files last a long time if you care for them properly.
Easiest way to tell would be to pick up a new file and try it. If it works, then you needed a new file. If it doesnt, then you need to work on your technique.
That makes a lot of sense. I’ll try that
It is really short. Files go dull and don't really give any signs. 5 is a good rule of thumb, but some go as little as 3 or as many as 10.
Generally when sharpening a tooth that's like 8 TPI (standard ripping saw) sharpening should need less than 8 strokes for each tooth.
Also try soaking your file in vinegar overnight, they might be a lot better in the morning. It's to do with chemical sharpening, the vinegar dissolves some metal around the files teeth and they get a bit sharper.
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