View Full Version : File reconditioning?

Keith J
December 21, 2001, 05:54 PM
I had a few files that had gotten a little rusty from lack of attention etc and needed one for a project. It had no bite and was leaving a poor finish.

As it was next to useless, I figured a little cleaning wouldn't hurt. I did the standard, card, pick and brush but since its a superfine tri, none worked.

I carefully degreased it and used some phosphoric acid to remove the rust bloom. After rinsing well, I gave it a coat of Kroil with the file still wet with water to prevent rust, letting it dry on top of a warm stove. Kroil displaces water and flows well.

Much to my amazement, the file returned to a near original performance. I had been using it on hard parts and am thinking the rust was mainly burnished-in steel and other stuff. Pickling it in phosphoric acid removed the adherant rust and other gunk.

I then tried it on my long-angle lathe file and mill bastards with great results.

December 21, 2001, 08:09 PM
Acid of various sorts is an old-scool machinist's trick for sharpening dull files. Acid removes material from all surfaces simultaneousely, leaving rounded edges nicely sharp. Make sure your file is clean first, as the acid typically eats the steel faster than it eats what's clogging it, which can leave dull spots.

December 22, 2001, 12:18 PM
I have a few old,dull files that are waiting around to get made into wood lathe tools. This idea might give them a second lease on life...Is the phosphoric acid you used the same stuff that gives naval jelly its bite?

December 23, 2001, 12:00 AM
I was once told by an old man that knew tools, that you never drag your file backwards across the work as this collects trash and dulls the file. A file is supposed to be self cleaning, if you only push it across the surface you are working on the cutting edges throw out the waste product. :)

December 23, 2001, 12:16 AM
Great tip.

I have at least a dozen large files clogged with junk I was going to make into knives until I determined I could buy an excellent knife for 100 bucks... Also some rare Swiss files #3 and #4 that don't respond well to the card.

Where can I get some phosphoric acid? Other than Coca-cola...

Joe Portale
December 23, 2001, 06:27 PM
Phosphoric acid is pool acid. Although it is watered down a good deal. Look in the yellow pages under "Chemical suppliers". It is relatively cheap. In another part of my life, I do photography and use phosphoric acid as a developing agent. Costs about $13 a gallon for the lab grade stuff.

Here is another old timer's file trick for anyone who cares: WHen filing soft metals, like aluminum or brass, rub chalk into the teeth before working the metal. The chalk keeps the teeth from clogging up.

Merry Christmas and Happy New Year to all!!!

April 10, 2008, 05:06 PM
I keep all old my files greased.All of them.I wash them in solvent to use,.I normally lightly chalk them for all metals.I use them.I clean then.I grease them and store them in containers.The big ones in 5 gal buckets.The files that I bought new look new.The ones that I picked up at flea markets to clean up and use show abuse.These flea market files were a hit and miss method of picking up a few good files as are the "China" files of today.Some are great,while some will not cut butter without heating the butter.I shopped for files with a small piece of tough,but not hardened tool steel.Also.Some of the courser cheaper files are good for woodworking.Our Southern Seasoned live oak can be worked with a file and can replace even a slow speed Brass or Bronze bushings that you can no longer find to fit along with various barrel bushing,spacers and even recoil lugs in long arms.A seasoned piece off a beach front coastal Live Oak is a treasure when you need it.Now it is as difficult to work as the British found old IronSides.Think "Iron"when you do.

I dissolve a soap based Marine grease in Mineral Spirits (Indoor use)naphtha (Colman Fuel for outdoor use) in a quart jar.I then put it in spray bottles to use.You have to shake it up to use.Don't miss mixing what is in the tube as it will settle out.This will get grease in every tiny crack.I use the various penetrating oils on things but they do not seal out rust like a good marine grease.I use the cheaper ones like Wal-Mart for this.I use this on guns for storage with good results.It gets EVERYWHERE.The old GI bore cleaner helps in cleaning a file in my belief and preserves them.Now that it is scarce,I use what little I have sparingly.If you have a excess,try it.


Bill DeShivs
April 10, 2008, 05:55 PM
Hydrochloric (muriatic) acid is sold as a concrete cleaner. It will clean files.

April 10, 2008, 06:07 PM
The acid trick kinda works one time, but it tends to round over the cutting edges, thereby dulling the file. Better to take good care of them and buy new as required.

April 10, 2008, 08:24 PM
Muriatic acid will work, but remember it is very hydroscopic and will pull moisutre out of the air, If you use it best to wash the file down with a detergent, dry and lightly oil the file. Many years ago ( like 40)I used to do some concrete finishing. The Brick masons used Muriatic and water to clean the mortar spills off of the brick work ( it disolves cement quickly too, also leather boots) I figured it was a great way to quickly clean my trowels. I washed them down with the acid and put them in the back of my truck, the next morning they were covered with rust and I mean a lot of rust.

April 11, 2008, 11:20 AM
I'm not an expert but I read once (and Alfred may know) that you can heat, or maybe boil, sulfuric (battery) acid until it smokes to concentrate it and it will supposedly clean or sharpen an old file.
I've always meant to try it but never got around to it.
I think I read it in an old military manual.

April 11, 2008, 01:45 PM
Dan.I worked with Sulfuric Acid including daily hooking up and disconnecting RR tank cars,piping,pumps,meters and such for well over 30 years.We used a little over a RR tank car a day normally.We were extensively trained and retrained yearly.I was in maintenance & emergency response in a chemical plant.Heating weak Sulfuric is dangerous.If it is in a iron container or has iron particles in it it can react with the water in it,release hydrogen and explode.I personally know of a Sulfuric acid pipeline doing this at our plant when being welded on years ago.The line had been flushed with water,As most know who work with it,weak Sulfuric acid will react far better than strong or 98 degree Sulfuric.We used Iron piping for Sulfuric Acid pipelines until the 80s.We then went to a plastic type of polypropylene lined.It will dissolve nylon and cotton clothing!

Weak Sulfuric Acid was concentrated in a series of 3 evaporators at one time.I don't know about now.You can heat Sulfuric in a container and once it starts boiling it can empty the container without stopping even with the heat cut off!

Weak or watered down Sulfuric will eat your metal better than stronger but is poor beside Phosphoric.Phosphoric was commonly used as a surface "rust killer"on metal before painting.Thick or heavy rust we still sandblasted,chipped and wire brushed.

Be careful.I have coughed white foam for days from Acid & Caustic mist and fumes.I also wear the scars here and there from them on my body and on one eyeball.

My recommendation is If you have to boil sulfuric,Get someone you really hate to do the boiling and use your ex's best pot.


April 11, 2008, 06:29 PM
Avoid sulfuric, nitric, and hydrochloric (muriatic, or pool) acids. All will activate the metal surface which make it vulnerable to rapid corrosion. Sulfuric and hydrochloric are used to "pickle" metal for plating because of this property. Nitric is used to passivate stainless because it attacks free iron so effectively. But if you have been paying attention, you'll have noticed that cold blues using nitric or hydrochloric acid in the mix all suffer after-rust pretty badly if you don't neutralize and treat the surfaces immediately after using them.

Phosphoric acid, on the other hand, tends to leave a phoshpate layer behind that actually helps provide the metal with some corrosion resistance. It's like micro-Parkerizing. The cold blues that use phosphoric acid, like Brownells' Oxpho Blue, or Van's, don't tend to exhibit after-rust.

Phosphoric is pretty commonly available as a concrete cleaner, though many use hydrochloric, too, so look at the labels. Lime Away, and some of the rust removing compounds are also phosphoric acid based.

April 21, 2008, 09:58 AM
You guys are amazing. I think I'll pass on heating the sulfuric unless I use Alfred's wonderful suggestion. I never would have thought ex wives would be good for anything.

Unclenick, I've used phosphoric several times for home parkerizing.

Speaking of which, I've noticed on some forums that guys use steel wool and other chemicals in their parkerizing solutions and cook at high temps until the parts stop gassing. I just did as the gunsmith told me and used phosphoric and water and cooked at a temperature not to exceed 170 degrees (if I wanted to reuse the solution) until the piece got the color I wanted. The longer I cooked it, the darker it got. My finishes always came out nice and (different shades of) gray. Then oil to set or cure the finish. And I've never had rust problems afterwards. I bought some manganese dioxide to try a black finish but haven't gotten around to using it yet.
I also like the way a parkerized finish holds oil.

April 21, 2008, 11:07 AM
As mentioned to use chalk on files. My grandfather showed me this a long time ago and he used soapstone instead of chalk. I have found that the soapstone adhears alot better and lubricates the file due to the almost waxy residue. And it makes cleaning your files afterwards alot easier. You can pick up soapstone at almost every welding supply store and a few sticks go a long ways. And it comes in round, square and flat shapes for those special shaped files. Just wanted to share a little of my knowledge and hope it helps someone.

James K
April 21, 2008, 12:08 PM
Just don't even try to buy a file card locally. 99.9999% of hardware store clerks will send you to the nearest stationery store or even to a computer place for flash cards.


April 21, 2008, 12:32 PM

The finish you will have achieved will be an iron phosphate finish, not Parkerizing, as iron is the only metal available for the acid to act on there. The military finishes are Zinc and Manganese phosphate, and they are what the chemicals made by the Parker company provide. They have different durabilities and porosities and thicknesses, and different degrees of corrosion resistance and surface roughness and lubricity. You select the one whose properties you desire most?

The manganese phosphate is heaviest and darkest and, arguably, the most durable of the Parkerizing formulae. The zinc is considered to be the best base for a painted finish, like Duracoat or Gun Kote, owing to its higher porosity. Iron phospate gets used frequently as temporary protection and an anti-splatter surface for welding. This is the first I've heard of it being used for a final finish, though? I'll have to experiment with that and see how it does? What was the dilution you used?

Harry Bonar
April 21, 2008, 03:01 PM
I just get new files.
Harry B.

April 22, 2008, 04:24 PM
Jim.You got me to laughing and it hurts!

"I been in the hardware business for over 40 years.If there was such a thing,I would know about it"!"There is nothing that I don't know about hardware'!Does this sound familiar?After I got the stock number for him to order it for me from his supplier,he refused."I don't like people going around trying to make a lier out of me"!I told him "it was not trying"."You lied and you did it all by yourself with no help from me".I bet I got 50 people to ask him to order them a file card.I carried one in my truck dash to show him every time I saw him for years.He was a very valuable,important and intelligent man in his own mind.It seems we have many such every where.

I am fortunate as I am stupid but at least I know it.I have found many stupid like me but did not know it.I figure that makes me smarter than they are.


April 24, 2008, 09:31 AM
I first started with a gallon of solution I bought from a local gunsmith. I'm not sure what was in it but it was clear and I used it as he told me to and the parts came out a nice light gray. I then found a little booklet (I think it may have been at a gun show) titled "Home Parkerizing" or something to that effect. And it called for the acid and water and that's what I used from then on. That solution never gassed and the longer you cooked it, the darker gray it got.
I read online about the manganese dioxide and steel wool ingredients and was going to use that the next time I refinished something. I also got some zinc oxide from work and was going to try that also. What I understood was the zinc gave you a gray finish and the manganese dioxide gave you a black finish.
I don't remember the water/acid ratio and was going to get it online the next time I needed it. My little booklet burned up in a house fire last summer and it's been a while since I mixed up any.

April 27, 2008, 05:50 PM
My little booklet burned up in a house fire last summer and it's been a while since I mixed up any.

Hmmm, why does this not surprise me.......:)

May 7, 2008, 06:44 PM