View Full Version : How do they do that?

05-06-2004, 04:33 PM
'Nudder dumb question: How are files manufactured? Anybody ever seen the process? The question came up the other night and darned if I knew the answer. I did a Google search but couldn't come up with an answer.

They're hard as Superman's kneecap and are pretty cheap to buy so it can't be that complex. Are the teeth ground on after the hardening process or before? I'm just glad we don't all have to make our own like they did in the old days.


05-06-2004, 05:18 PM
Here is how they used to do it.


05-06-2004, 05:31 PM
Wow, 22,000 cuts per half-round file...by hand! Amazing. So much for the good 'ol days! http://bbs.homeshopmachinist.net//smile.gif

I wonder how it's done now.

Peter S
05-06-2004, 06:08 PM

05-06-2004, 06:12 PM
they are cut by machine now, most files are what they call 95 points of hardness, while the old ones were over a 100, if you order industrial files, the will be about 105 points. informaation from a seminar attended several years ago.

05-06-2004, 06:34 PM
There is a Nicholson file factory in
Cullman, AL. My tech school teacher reported
that the one time he visited he was told they
have a high worker turnover because of the
noise. Even with earplugs and over ear
hearing protectors the din from the machines
was horrendous. I got the impression of dozens of machines hammering at high speed
on file blanks. Steve

05-06-2004, 06:47 PM
Great websites guys....ya'll are better'n the Shell Answer Man!

Toolmaker Extrodinair
05-06-2004, 10:09 PM
used to be a company in Xenia, Ohio that resharpened files by immersing them in a solution. not sure what or if they are still in business.

05-06-2004, 10:47 PM
We used files by the thousands. A company is Texas obtained a contract to "re-sharpen" them. I was told the files were pickled in acid to sharpen. The men who used the files claimed they (the files) were worthless in a short time. Others said the process was common and did work- if and only if the files were really clean. We did not re-new the contract.

05-06-2004, 11:45 PM
File sharpening in acid is the common, and maybe the only, method of sharpening files.

Way back in college a professor talked about the process. Apparently the acid only attacks the flanks of a tooth and not the sharp edge. He said nobody understood the exact reason the acid didn't attack the sharp edge.

05-07-2004, 01:45 AM
I wonder if it's possible to look at the actual edge of a tooth with a microscope, while immersed in acid. I bet it would show that the acid molecules need some minimum surface area to be in contact with to do the etching. This would preclude the actual edge itself from being etched. Just MHO, a static discharge from the grey matter.
Fascinating read on how files are made. For some reason I started to envision an early lathing operation as one where one guy would turn the spindle, and six others would file on the rotating workpiece. Then someone brings out the 'calibrated' wooden forks to check the diameters. The last and quality control guy would then use a meatloaf stone to make the finish cuts. The final product then is shipped off to the Congo, where it gets heat treatment just by passing through, followed by stress relief on a cruise ship in the Mediterranian. In those days, the filers had to do double duty as oarsmen for the ship.
Sorry, I guess the idea of someone chopping at one file 1000 times with a chisel just didn't tickle my rational lobe. I'm not denying that's how it was done, though. Amazing.

[This message has been edited by darryl (edited 05-07-2004).]

05-07-2004, 01:48 AM
It's really not complicated. If you have a shape like a V with a radius on the point and etch it equally so it becomes smaller then the radius of the point becomes smaller, that is, sharper. Also, if the point has a very thin burr on it it doesn't take much etching to remove that burr. If you etch for too long though then you lose the effect and the surface becomes smoother. That is how electropolishing works.