# Rasp and File Sharpening



## Gregn (Mar 26, 2010)

Has anyone heard of sharpening old rasps and files using vinegar or other mild acids. If you have was it worth the effort. I've heard that when using vinegar you need to immerse the rasp or file for 24 hours.


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## swirt (Apr 6, 2010)

Yes, I've used white vinegar often. It works well on files, and moderately on rasps.

The first step is to make sure you get any grease and debris out of the teeth. Grease or oil or dirt may prevent the vinegar from reaching the steel and etching it. I use a brass brush with some dish detergent or a bit of ammonia and water to scrub them and get them as clean as possible, then go right into tube of white vinegar. I often just use a tall narrow flower vase, but some people glue a cap on a piece of PVC and use that.

At least 24 hrs…. inspect and have another go if it doesn't seem to be done yet.

When they are ready to pull out, I rinse them well with running water and a bit of dish detergent again with the brass brush. As soon as I get them all well rinsed, I blot them dry with a cloth then spray them good with WD40 to prevent flash rusting.

Somebody did a nice video on this recently… I'll see if I can find it.


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## swirt (Apr 6, 2010)

Found it http://www.logancabinetshoppe.com/1/post/2010/12/quick-tip-7-sharpen-a-rasp.html


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## Gregn (Mar 26, 2010)

Thats where I heard about it. Was wondering if that worked as well as he claimed. I kinda wondered if it worked with the rasps as well as its suppose to on files.


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## bobsmyuncle (Jan 12, 2011)

I've used Boggs Tool in CA. I don't remember what it was, but it seemed to be just about a couple of bucks each, with the first couple free for new customers. If it's beyond sharpening, they won't try and will either return them if you want or discard to save you return shipping charges. They claim they will even improve sharpness on new premium files such as Nicholson #50 and the like.

http://boggstool.com/index.htm


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## DrDirt (Feb 26, 2008)

Ditto on Boggs in California.

Marc Adams class making the maloof rocker tried them out as well and compared sharpened by Boggs with Brand New Nicholson #49's and the sharpened ones performed better than new shaping chair parts.

Boggs calls the process liquid honing - - so I kind of suspect they are doing the same thing that swirt linked to but on an industrial scale, and maybe with some stonger chemicals.


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## tenontim (Feb 24, 2008)

Interesting video. I've got a couple of files and rasps that have been banished to the scrap box, I'll have to try this on. Thanks for the link, Swirt.


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## Gregn (Mar 26, 2010)

I figure its worth trying as its the fine side of my rasps that are dull. Hate to discard them to the retooling department in the shop. Definitely have enough files I'd like to still use again.


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## Gofor (Jan 12, 2008)

Looks good and I'll try it. However, I do have one disagreement with the video: The statements about "brown rust" are totally inaccurate. Brown or reddish rust is ferric oxide, which is active corrosion. It will continue to eat the underlying iron. "Black" rust is ferrous oxide, which has used up all the oxygen and sealed the surface, so is no longer actively eating the iron. Ferric oxide is soft. Ferrous oxide is hard and brittle. A good example of ferrous oxide is the mill scale on a piece of hot forged angle iron, etc.

One way to prevent the rust ring at the surface of the acid is to coat it with a little vaseline or grease.

For valuable or expensive rasps, do not use a stronger acid [phosphoric, sulfuric, or muriatic (hydrochloric) acids]. Strong acids on hardened steel can cause hydrogen embrittlement. The teeth may actually break off, and the rasp could shatter if dropped on a concrete garage floor, etc.

Go


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## swirt (Apr 6, 2010)

That's interesting info Gofor. Is there a way to force one kind of rusting vs the other?

Thanks for the tip about the grease on the tang. In the past I have not worried about the bit of rusting on the tang as It comes off in the final rinse and brushing. I usually wipe the tang with BLO before pounding on a new wooden handle as a minimal bit of precaution.


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## FatherHooligan (Mar 27, 2008)

I've learned something this evening, thank you.


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## Gregn (Mar 26, 2010)

I assumed that he was referring to what was called rust bluing that was done to guns at one time. Although with following the tip of a little vasoline or grease it shouldn't be that big a deal. It will just be nice to put new life into some old tools.


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## TopamaxSurvivor (May 2, 2008)

EDIT: I see that is a cabinet shop, guess I'd better put my specs on, eh?

Browning is the traditional way to finish a barrel. Just let it rust, keep it smooth and control it with a little oil.

I learned something too, Never heard of this B4 )


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## Gofor (Jan 12, 2008)

When browning a gun barrel, you are letting it get a uniform coat of active rust, and then stopping it in its tracks by sealing it from oxygen (using gun oil or linseed oil, etc). The oil is the protection, but soaks into the microscopically rough rust, so it isn't "shiny". The rust layer is the light defractor so no glint off the barrel alarms your prey. A very effective way to achieve an easily maintained matte finish on an item subjected to a lot of temp variation when fired, abrasion and environment when in field conditions, and the the attack of the corrosive gunpowder (term used loosely for this explanations) compounds it gets contaminated with. Works well as long as the gun is properly maintained with the oil. If not maintained, the oil gets rubbed off, or evaporates if cheap oil is used, or the corrosive gunpowder compounds are allowed to remain on it, and oxygen gets the surface, so rust becomes active again, resulting in pitting.

The black rust is where the iron and oxygen have come to a balance and from a chemical standpoint have become inert. The molecules are so tightly locked that moisture and free oxygen cannot penetrate them to attack the underlying iron. It occurs on the hot forged steel due to the high temps of the process, and the control of the gasses that are allowed in the oven. The other place you may see it is after using some of the commercial rust removal/stabilizer products like "Naval Gel", etc, which are usually a phosphoric/chromic acid combination. They dissolve (oxidize) a lot of the active rust, but where it is heaviest and oxygen depleted as in a deep pit, results in the rust becoming inert. (A process also called passivation). This protects the surface well, but is brittle. On a flexible item like a thin steel car skin (fender, etc), it can crack, allowing moisture and free oxygen in to start the process over again. On heavy iron pieces, this occurs more slowly, as they do not flex as much.

As applied to sharpening the files, if the rust ring occurs, and you keep it coated with oil or remove it, no harm, no foul. I just wanted to alert people that by itself it is not a protective coating at all, but the opposite, so don't just let it set there.

Sorry to cause confusion. Hope I explained it okay.

Go


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## Gregn (Mar 26, 2010)

Gofor, Thanks for the education. This has been a pretty interesting thread.


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## TopamaxSurvivor (May 2, 2008)

Thanks Gofor, I never knew exactly what the diference was, but browning is a lt easier to do. Matter of fact, a gunsmith trying to blue a Douglass barrel could not get it to color. He took some old Birchwood Casey Browing solution (no longer available, new stuff it tame) to start it browning. Once that happened, he was able to blue it.


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## Dark_Lightning (Nov 20, 2009)

Interesting. I'll look the information over, but I'll point out one thing I know about making surfaces smooth. And it involves the same sort of process. Acids will combine with the sharpest/smallest parts of the metallic item first, eroding them off, making them smooth. It's called electropolishing. Stopping corrosion is another deal entirely.


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## swirt (Apr 6, 2010)

Gofor, thanks for sharing all that info.


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