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Guilty

https://www.popularmechanics.com/home/t ... rrect-way/

The article says that files cannot be sharpened.
However, a file left in the back garden to rust for a month in the rain will in fact become sharper.
This also works in the front garden.
I know this makes no sense but it is true.
Files that have been damaged by cutting in both directions can be rescued using this method.
A damaged file can easily be recognized because it will be more likely to skate instead of bite and the tops of the teeth will be shiny.
Similarly files damaged in this way can be acid etched to improve their cutting ability.
I realize this advise is counter intuitive but it really does work.

Honestly, I think it's a bit pretending. Belonging to the "I know better than you peasants do" serie.

If the teeth might be bent and permanently damaged by simply pulling the file back, goodness only knows what might happen to them by pushing them forward.

Has anyone ever damaged the teeth of a saw by pulling it back perhaps?

So I'll continue to use my files in both directions without any concern at all.

I do see your point. However, if you consider the geometry of a single file, (or saw), tooth, you will note its "buttress" form. Pushing the file forward, the cutting edge is well supported by the buttress. However, stroking backwards, that same cutting edge is now at peril of breaking away, or folding over, due its lack of support/bracing. In metal working, a carbide tool bit will perform well all day long when used as directed. However, in the case of a lathe for example, if the machine is stopped while the tool is still cutting, then reversed while tool pressure is still exerted on the workpiece, the carbide edge quite often will chip off.

Besides, exerting force on the backstroke while filing or sawing is wasteful of effort, at the very least, since no real cutting action occurs then anyway. I was always in awe of my father, who could use a handsaw extensively and never seem to exert himself in the least. He explained that my fatigue was due to wasting my efforts by applying down force to the saw while on the backstroke.

I'll cite another couple of examples as well. I have a power hacksaw. There is a "cam & ratchet" device in it's design that lifts the blade away from the workpiece when the saw begins its backstroke. It then lowers the blade when the cutting stroke begins.

This example is a bit obscure if you're not in the gear cutting trade. A Felloes Gear Shaper has a very specialized cutting tool for manufacturing gears. The tool strokes vertically, up & down, as it cuts gear teeth. The downstroke makes the cut, and you guessed it, on the upstroke, the workpiece retracts, pulling it away from the cutter, in order to protect the cutting edge.

On the other hand, there are literally millions of motor jigsaws (my unit included) in which the saw goes simply up and down with absolutely no retracting of the saw on the back stroke, and the saw itself is absolutely not damaged by this in any way and nothing else "weird" happens.

I perfectly remember when top-of-the-range jigsaws with swinging saw were introduced, and the commercials said the purpose was to quicken the cut, not by any means to save the teeth of the saw.

As a final note, there are some cases, especially with metal sheets, when the saw engages with the piece jumping all over and there is no other way to cut it than to gently pull the saw backwards. And yes, it does cut also when pulled backwards, as anyone can experiment by himself, although of course with less performance.

Marco,

Jigsaws are primarily used for wood. Continue to file or saw as you wish, with happy abandon.

The science of cutter morphology be damned.

Have to agree with you. Especially considering the cheap mass-produced files most of us have. I have used them in both direction and noticed no detriment in cutting.

That said, I would not use a $40 Swiss-made file in the same manor as a cheap $5 file (last time I bought a file new at retail was at Ace Hardware and they were $5 20 years ago! )

You guys aren't also needle turners are you????