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· Registered
1,035 Posts
Discussion Starter · #1 ·
I heard about this trick a while ago and decided to try it and see if it works. It's said to be an old blacksmith's method to restore dull files. What you do is not to mechanically sharpen the file, instead you chemically etch it.

I had an old file wich has become rather dull. It's a good quality Öbergs file so I'm reluctant to just throw it away. First I cleaned it up with a file card.

The liquid you use to etch it is a mild acid, could be vinegar, citrus acid or something similar. I used white vinegar (12%). I filled a glass with it and put the file in. This will of course only affect a part of the file, but I was interested to see the difference.

Bunsen burner Metal

I let it sit for 24 hours, and this is what it looked like. Absolutely clean and with a darker grey colur.


I neutralized the acid whith lye, brushed it off under water and dried it with a heat-gun.


It looks like new, and feel like new. When I tried it I could notice a significant difference between the treated part and the untreated, so obviously it works. Now all I have to do is to find a suitable vessel to put it in. I don't want to use a full bucket of vinegar :no:.
Maybe a PVC pipe with an end cap?.....

BTW, it's said to work on rasps as well.

· Hobbyist wood-butcher
1,587 Posts
Thanks for posting this. I will have to try it out... have a few old files that I have picked up in various garage sales and what not.

My first thought was a PVC pipe with an end cap. I suppose you could neutralize the vinegar with baking soda as well....

Thanks again

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