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Resurecting "worn" filesHits: 1568
Dave Brown [quahogwi]
on 05/14/01 05:55pm
[     ]
To all:

Today I had the urge to do a little experiment. So, I did it and was pleasantly pleased with the outcome.

I have lots of old files around the shop, most of which couldn't deburr a stick of warm butter. They've been in a pile for quite a while and I was gonna send them to that Boggs fellow out in California (Boggs Tool Precessing) for his reconditioning thingie. But, today I thought ... (and don't act so surprised )

Over the years there have been several discussions about this reconditioning, acid baths for files, etc... in several discussion groups. So I decided to follow up a bit on some of the things that have been said.

I have a tub of moderately used mild phosphoric acid solution that I use I've been using in the shop lately. When first mixed it was probably around a 15% solution, give or take. I've descaled a bunch of stuff in it, and de-rusted some other stuff. The liquid is a bit dirty looking, there's probably been some evaporation, and I have no idea of the current strength. But I do know that I can leave something in it overnight and it's just fine in the morning, excepting for the fact that the rust/scale is gone.

Anyway, this morning I put one of these old worn files, double checked to see that it hardly touched mild steel, and put it in the acid bath, put the cover on it, and walked away to do other more pressing things. This afternoon, about 7 hours later I remembered the file and took it out. It looked OK, except the rust was now a soft black oxide. I rinsed the file off (wearing rubber gloves, rubber apron, eye protection, etc...). The black oxide just washed off with normal water faucet pressure. The file was nice and grey and the teeth looked clean. Fearing rust, I sprayed it down with WD-40 to displace the water, then gave it a dip in some acetone to remove the WD-40 residue. (the WD-40 and acetone rinse were probably unnecessary at this point, but I did them anyway).

The file was looking pretty good. I got the same piece of steel out that I had used in the morning to verify the dullness of the file. The file now cuts it like a new file, or at least like a file that has hardly been used.

I'm pretty sure that the main thing that the acid bath did was to clean out all the built up filings and rust embedded between the teeth. What else it actually did to the teeth I don't know. What I do know, though, is that the rest of the files are going into the acid late tonight and will get rinsed and dried in the morning.

I'm thinking that I really have a bunch of good files in disguise as opposed to a bunch of old worn our files destined for the forge and a new life as some other kind of tool. I'll do this later when the acid bath doesn't bring them back anymore.

For those who are curious, I got the phosphoric acid from Fleet Farm. It's in the dairy equipment cleaning supplies area and is called "Milkhouse Brand STONESOLV milkstone remover and acid bath". It's about a 42% phosphoric acid solution in the jug, and also contains some surfactants. It isn't necessarily cheap, but is isn't expensive either. All things considered, I think it is worth it.

Replicate this at your own risk.

Dave Brown 

  Subject Author Date
*  Resurecting "worn" files Dave Brown 05/14/01 05:55pm
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