File sharpening

[JackP]

The subject came up on this forum the other day so thought I'd try what I had heard of for many yrs.

I first cleaned and degreased 4 14" long angle lathe *******s files. they are very old and very dull. they have been used for years to back up sand paper while finishing bearing fits on shafting in the lathes at my shop.

I put 1/2 gallon of white vinegar in a shallow pan. I left the files lying in the vinegar for 4 days turning them over and inspecting them every day. at the end of day 4 I hosed them off them blew the water off the coated them with WD-40 to displace the water.

They are now very sharp and cut as smooth as new ones. they may actually be a little sharper than new files.

Give it a try. I might try regular vinegar next time.

Jack

 

[Grizzly Adams]

That's a neat trick! I suppose the vinegar just erodes off the surface of the file leaving fresh metal exposed?

 

[jerrywh]

10% nitric acid. 10 or 15 minutes.

 

[Zonie]

I've heard others say that some sort of acid treatment or another sharpens files.

I have yet to figure out how this can work.

I don't doubt that a acid like vinegar will clean out the bottoms of the files teeth.

How it would sharpen the cutting edges though I can't figure.

Acid will dissolve steel. Vinegar just takes a lot longer.
Anyway, if I visualize a sharp cutting edge on a brand new file, it comes to a very sharp point.

Although the acid will start removing the surfaces that form that sharp edge, it will also attack the sharp edge.

As I see it, if the surfaces got .005 of material removed, the sharp cutting edge would also have .005 removed creating a rather dull rounded edge.

For what its worth, file teeth are punched into the file with automated machines that drive chisels into the surface.

This is somewhat like people forming a dovetail by driving a chisel into the metal and displacing it except with a file, the sharp cutting edge is left sticking upward.

Anyone want to educate me on this? :hmm:

 

[agill]

I would have to agree with Zonie. I think what is happening is the acid or vinegar is cleaning rather than sharpening. Either way, it is something I have not tried, but seems like I need to since it sounds easy to do. In the past I only used chalk to keep the teeth cleaner and a file card brush to clean the teeth. It worked fine, but required some effort. I like easy better.

 

[bpd303]

When my files get too dull to cut I send them out to this company. Never had much luck with acid, other than cleaning them. http://www.boggstool.com/

 

[Stophel]

I was told to try muriatic acid, so I did a couple of weeks ago on some files at work. Now, I only left them in for like 15 minutes.... I don't know if leaving them longer would be more appropriate or not, but, they were fizzing and bubbling pretty actively, so I didn't want to leave them in much longer, and I sure didn't want to leave them overnight! The result was that the files were nice and clean and FELT sharp to my fingertips. However, there was VERY LITTLE improvement in actual use.

:idunno:

 

[Zonie]

I can understand how "liquid honing" would sharpen a file.

The honing material is blasted along the tapered backside of the tooth towards the cutting edge towards the front of the file.
This would remove a small amount of the tapered surface on the tooth and when the abrasive reaches the cutting edge it just flys off into space leaving a sharp edge.

I noticed the company that does this process says a really fine toothed file can only be sharpened once before there isn't enough "valley" or tooth groove under the cutting edge to allow it to cut.

 

[Brokennock]

I agree it must be that the vinegar just cleans the files valley or grooves really well, the cleaner valleys allow the file to cut better because there is somewhere for the cut material to go. I know that when I vinegar patina a hair popping razor sharp knife blade, it is still sharp, but know where near as sharp as when it went in the vinegar.

 

[kaintuck]

#2 for Boggs......they have a bunch right now of mine.....so, send me all your tired, rusty, worn out files.... :grin:


Marc n tomtom

 

[JackP]

The files that I put in the vinegar were extremely clean. The teeth were so dull on one of them they shined a little. Try it and educate your selfs. Vinegar is real cheap, files are expensive?

The file sharpening companies use acid, why shouldn't it work for us? We used to send them off at a shop I worked at 35 yrs ago and all of them were sharpened with acid. It works.

Jack

 

[vulture]

I don't mean to hijack this topic but I need to ask, what brand of files do most of you use? I have had some files imported from some place, sorry don't know where, that I picked up at a very special price years ago, folks had several boxes of them sitting on their counter and even then the price was very good, so I got two of each size, wish I would have purchase a dozen of each size, some of the finest files I have ever been able to get my hands on, but they are wearing out now and the hardware store files don't seem to be up to much. I don't mind paying a decent price for a decent tool, but hate to order something said to be wonderful only to find out I paid high dollar for junk.

 

[M. De Land]

I have a sand blast chamber I use a lot for barrel work and wonder if it could be used for sharpening files?
Perhaps glass beads would work better than sand.
I'll have to give it a try and take a look before and after under magnification. Mike D.

 

[kaintuck]

prob a german or swiss file they are wonderful!!!

and $$$

marc n tomtom

 

[illuveatar]

I just take my old files to the forge and make a blade out of them. Folks at the local flea market sell old Nicholson and Disston files for a buck a piece. Most are still in new condition despite being decades old.

 

[LRB]

I have a sand blast chamber I use a lot for barrel work and wonder if it could be used for sharpening files?
Perhaps glass beads would work better than sand.
I'll have to give it a try and take a look before and after under magnification. Mike D.

Worth a try. I would say direct the blast from the tang end forward. Maybe try one sand and one bead?

 

[jerrywh]

Bumble Beas can fly and acid sharpens file really well. I have been using the acid method since 1961. Some Chinese files are not tool steel. They are only case hardened. Acid will eat through the case and the file will be no good. Good old American files will always sharpen. I only buy the best. Nicolson or Grobet.
Sadly most people don't know how to file Or saw metal. They saw metal like wood and file the same way.
I have never found a way to sharpen a #8 or #6 cut file. The teeth are too fine

 

[JackP]

In a few days I'm going to try to sharpen some chainsaw drag files. I'm hoping the mild acid in the white vinegar will do the trick on the very fine teeth.

I sure can understand why anyone would think this can't work, I guess that's why I waited so long to try it myself.

After they tried my vinegar sharpened files at the machine shop they drug out old files from everywhere wanting them redone.

Think I will take some short pieces of 3" PVC, put a cap on one end and make a few tubes of varying lengths for the vinegar baths.

Let you know how it comes out.

Jack

 

[davec2]

Zonie,

In the rocket engine business we often used an etching process to deburr parts that have holes drilled into blind passages. The etching does fine to remove burrs but it will also sharpen any edge that is etched as well. For example, a hole drilled at 90 degrees to a passage - when etched, the break through edge of the hole is now more acute than the original 90 degrees....i.e. it is sharper.

On a file tooth, the acid etches primarily on the flat top surface and the bottom (gullet) surface. Where they meet at the edge just gets sharper because there is hardly any surface to etch directly. If you want to prove this to yourself, take a small piece of thin steel (like a piece of a broken knife blade or hacksaw blade) an toss it in the dilute acid Jerry H recommends. The piece will not etch uniformly in all directions. It will get a littler narrower, but a lot thinner until you have a very thin piece with very sharp, etched, edges.

I have been sharpening files as Jerry does for 30 + years. The files must go into the acid bath clean to start with or the etching will be splotchy. So the process is really sharpening the teeth not just cleaning out the gullets. I have sharpened rotary files like this as well and, in certain cases, sharpened a brand new file this way as the etched edge is sharper than the way the file comes from the factory.

Actually, these days, I just send them in big batches to Boggs. Certainly more time effective and the acid would cost me as much as paying Boggs.