I was using a rat-tail rasp this morning and noted my comment on it that it had been sharpened.   Did you know that you can have sharpened files, rasps, and other such tools?.

 

I have used Boggs Tool https://boggstool.com/.   They cost just a few dollars each.  Since you have to pay shipping, it pays to send a few at once, or get together with a buddy.  If the tool is beyond sharpening, they will discard or return at your request.  They told me they'd make my Nicholson patternmaker's rasp sharper than new. 

A soak in a 10% solution of sulfuric acid for an hour or so and, a rinse with bicarbonate sods and water will do a passable job. At least, until you can have them done professionally.

Keith, I didn't know, care to elaborate? How do they do it? I have some very nice rasps that I'd love to get freshened up.

Something you could try at home.  More on YouTube.  Some use white vinegar.  Never personally tried to sharpen a file.

 

 

 

 

Some straight ammonia will clean off the gunk very well.  I used it for scrapers, sawblades and files.  Of course, it doesn't sharpen, but will make things cut and scrape better once you remove the gunk.  If you use a brush, an old toothbrush or true brass bristle brushes do very well.  Leave the tool soaking for a couple to 3 hours, then brush.  Wipe off completely and wipe with paste wax.  

I keep a gallon of old battery acid around just for this. It really works.

Boggs tools seems to use acid and steam as part of their process. 

Spent a couple of hours yesterday with my patternmaker's rasp and was reminded of this company.  Bump.

I've sharpened both files and rasps with diluted nitric acid.  I used nitric because I had some - found it in my dad's garage after he died, he'd used it in some kind of spot assay method at drill rigs (gold exploration) - and more importantly, because I wanted to try ferric nitrate stain on curly maple.  I had tried ferric acetate stain already, steel wool dissolved in vinegar, and wanted to see if I could get the warmer color that seemed to come from ferric nitrate.

 

Vinegar is what I would suggest people try the first few times.  It is a moderately active acid, so a 5% solution will take a while to sharpen your files - guessing a day or so, maybe less?  With the nitric, even diluted to 5% like household vinegar, it will aggressively dissolve iron in a day.  I experimented with dull chainsaw files because I had lots of those around.  Left one in the nitric overnight and it was about 60-70% eaten through the next day.  I recall soaking for about 30 min to an hour with the main rasp I wanted to sharpen, an expensive hand cut one.

 

I've also heard of cabinetmakers using horse urine back in the day.  Kinda gross, but free and readily available in pre-industrial times.  I gather that it provides a very dilute and not especially active acid and that files can be soaked much longer.  Not going to try it though, vinegar is so cheap and my modern sensibilities can't get past soaking my tools in urine

 

I also rinsed with a baking soda and water solution when done.  It's surprisingly difficult to rinse away all the acid, so baking soda is a way to make sure it's all neutralized.

Edited July 14, 20242 yr by JWD

I have used Apple Cider Vinegar for rust removal on files and all sorts of steel. It will clean up a file just don't forget it is there or it may not be after too long. I am not sure this is sharpening but it positively cleaning up.