Renewing Files

[CPeter]

I acquired an older Milwaukee die filer (aren't they all older?) It came with a selection of files. They are dirty and have some rust. Can I soak them in something to clean and sharpen them, like say muriatic acid? BTW, the thing weighs 135 pounds!!

Peter

[rickyb]

Those files are hard to come by, so yes you want to save them. If they were mine I would clean them with a fine wire wheel. Wire size in the neighborhood of 0.007”. Brunch along the grooves of the files. We 40 will hold off the rust afterwards in a relatively dry shop.

before the naysayers chirp in…The wires are softer than the file and won’t damage it. Especially if they are thin and compliant. I’ve been doing it for years on the same files with no issues.

[rickyb]

Forgot to mention that any acid eats sharp points faster than surfaces and will dull the file?

[J Tiers]

Forgot to mention that any acid eats sharp points faster than surfaces and will dull the file?

Yet, the file sharpening services do use an acid treatment.

The acid has no idea what part is thin or thick. What it does is eat inward on surfaces. A triangular shape like a file tooth will be eaten at from both sides. If the "point" is blunt, the action of the acid eating away the metal will tend to make another sharp point. Since the point has little surface area itself, it wont be eaten as effectively as the other surfaces.

There are no doubt details that make all the difference. But the idea is sound.

[RMinMN]

Clean the files first. Any dirt or oils will deter the acid from doing its job. If the file have become clogged with material, us a hardwood block with a very sharp square corner to push along the file teeth and push out the material clogging them, then perhaps a wire brush or file card, then chemical cleaning using soap and an ultrasonic cleaner if available. Once the file is completely clean, then use an internet search to find how much of what acid for how long is needed.

[Rich Carlstedt]

I have heard to use Sulfuric Acid, not Hydrochloric
Auto Parts stores may have some for battery use.
Rich

My File brushes are very fine bronze wire, but I also use Maple Wood shaped like a chisel . Any hard wood should work

[J Tiers]

Yes.... hydrochloric acid (aka "muriatic") is "shop death". It will cause rust all over the place if used or kept in or near the shop. Sulfuric is not nice stuff, but it is considerably less likely to corrode everything in sight.

[chipmaker4130]

. . .Yet, the file sharpening services do use an acid treatment. . .

Maybe someone does, but those I've looked at all use an abrasive blast. From one well-known service: ". . .our ABRASIVE BLAST LIQUID HONING PROCESS to sharpen files and other small tooth tools as seen in American Machinist, Anvil's Ring and many other industry publications. Using steam, we relief-grind with abrasive blasting, taking material from the back edge of the tool to reform and sharpen the edge. Our process will give you the sharpest edge possible."

The prices are very reasonable too: https://boggstool.com/file-%26-rasp-services

[BCRider]

I've got some old Boeing Surplus files that were re-sharpened. They worked but they were no where near as nice as new files. Fine for roughing but the surface finish was not nice. From this I'd say one sharpening and then they are done.

I've also got a couple of straight shank triangle files which confused me as they cut on the pull stroke. I only found out some time later that files for die filers cut on the downward pull stroke... which makes total sense. So I'm guessing that the two I had and should still have around here somewhere are for a die filer.

[CLARKMAG]

I have put dull files in the microwave in a brine of salt and vinegar. They get sharp in minutes.

[Doozer]

I have put dull files in the microwave in a brine of salt and vinegar. They get sharp in minutes.

I think I might try this in the microwave at work first.

-D

[The Metal Butcher]

I think I might try this in the microwave at work first.

-D

About 10 minutes before lunchtime.

[Doozer]

Last time I put a black polyurethane U-cup seal
in the microwave to soften it. Not so good.
In for only 1 minute, it about caught fire.
It stank so bad, the boss bought a new microwave.
Thus is how Doozer's Shop ended up with a
microwave oven to heat my coffee. The smell
went away after only a few days.

-Doozer

[Tim Clarke]

Ya, Doozer! I love it when a plan gone bad pays unexpected benefits !!!

[boslab]

They are about, like

https://www.falcontool.com/PublicStore/product/Swiss-Parallel-Machine-Files,577,183.aspx

mark