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Hagerty
Hagerty Employee

There is a 50 percent chance you've been filing wrong

Somewhere between fact and fiction live bits of knowledge passed down from mechanic to mechanic. One that I have always felt a little passionate about is the proper use of a file. There is a correct cutting stroke, and pulling back on the file only dulls the edge produced by it.
https://www.hagerty.com/media/maintenance-and-tech/there-is-a-50-percent-chance-youve-been-filing-wr...
49 REPLIES 49
audiobycarmine
Technician

"Using the files on the back stroke removed a measurable amount of extra material from the steel chunk."...

Now who would have thought that the extra abrasion would result in that?!?
Kyle
Moderator

The teeth are formed with directionality and using the file incorrectly based on that design removed a decent amount of material. I would consider that interesting and borderline unexpected based on the measurements shared in the video.
DUB6
Specialist

   I was taught both ways by two different people.  I have to admit that I always thought that the "lift-on-the-backstroke" method was best, as it just seemed to me that it would result in less dulling of teeth.  But I've certainly done it both ways - usually dictated by how big a hurry I was in and how frustrated I was at the moment.  I did note years ago that when filing aluminum and other soft materials, keeping some contact on the backstroke did keep the file cleaner - and even removed a bit more material.  And I always figured that soft metal was not going to dull the teeth of a hard metal file.  But after watching this, I may try to watch the effects of both methods on my own projects to see if the test results look reasonable in real-world use.  Pretty sure, though, that I'm not gonna hold a toothbrush on my work the next time I'm deleting some material, smoothing out a rough edge, or rounding off a sharp corner.  It's an interesting question - which may mean that if I really find this interesting, my life may be a lot duller than my files, eh?  😁

Swamibob
Technician

Kyle:

I had a really funny response, while I was thinking Rob 'The Hack Mechanic' had written this piece, but that irony is now gone. 🙂
I do seem to remember; watching some old movie involving young German machinists, learning how to file, by hand, for a year or two, before they were allowed to start using machines. And yes, there was a specific way to file. YA!
eighthtry
Advanced Driver

Thank goodness for this new knowledge. It will "cut" my restoration efforts by weeks.

On a more serious note, thank you. I enjoy reading your columns and following your way-too-many projects underway at the same time.
GlennTurgeon
New Driver

Makes one wonder, why not have cutting teeth going both ways ?
DUB6
Specialist

Works on a bucksaw...

EventHorizons
Intermediate Driver

There is a story floating around (not certain of it's truthfulness) about a famous scientist who as a young lad was apprenticed to a machinist somewhere in Europe early in the 20th century. He was handed a rough 6-inch round hunk of metal and a file, shown a vise and told to make it into a cube of any size, equal in all dimensions and square to a thousandth of an inch.
He thought "this will be easy!"
He would file and file, take it to the master, who would critique it and send it back, and he would file and file and file some more. By the time he passed the test (weeks?), it was less then 1-inch square but he now knew how to use a file like a pro and had a whole new appreciation for what it took to make something!

Apparently the "cube from a ball with a file" was a fairly common training task for apprentices.
DUB6
Specialist

Sounds like something my dad would assign when he wanted me out of his hair for awhile...

Tinkerah
Engineer

When I was a machinist's apprentice (though later in the 20th century, and in America so possibly no correlation) I got to learn basic techniques on task that were boring but still useful to the shop. Like hand tapping hundreds of 6-32 holes in a customer's job, and having to recover any holes that I broke a tap in. To this day not only can I feel precisely how hard to push a tap before it breaks, but I can still recall the size they were.
Tcoradeschi
Intermediate Driver

Never called myself a machinist, but I spent some time in the early 80s as a machine operator. Basic task? Cutoff saw. Drilling and tapping was a step up! You do learn how to *not* break a tap after a while:-)

Oldroad1
Gearhead

WD-40 greatly reduces tap snap.
Lee
Intermediate Driver

Turning the tap counterclockwise to clear the tap of chips helps prevent broken taps. Chip buildup is the main cause of broken taps.
Lee
Intermediate Driver

Here's a way to tap without making chips. 

Use a Roll Tap.  https://www.yamawa.eu/wp-content/uploads/2017/10/Roll_taps_2017_web.pdf

 

And pair that with a Flowdrill and you have a awesome way to make treads in thin materials.   https://www.flowdrill.com/usa_en/

DUB6
Specialist

   @Lee - those are some interesting tools, and I've never seen nor heard of them before.  Thanks for providing the links - I'm intrigued enough to do some more investigating.  If anyone else has experience with these technologies, let us know!  🙂

jtchew
Pit Crew

In some fairly respectable venue, I read that this or a similar feat (it might have been the converse task of making a piece of bar stock into a sphere) was part of the long and difficult process of attaining the "artificer" rating in the Royal Navy in the between-the-wars years. I'll follow up if I get any traction on a reference.
61Rampy
Instructor

I've heard that story too. I believe that the "Master" was Ettore Bugatti, who insisted that his engines were as precision as they were beautiful. Not sure the story is true, but it sounds plausible.
elvacarsdallas
Intermediate Driver

What is the difference between a **bleep** and a mill cut? The pictures show what could be each.
elvacarsdallas
Intermediate Driver

I am sorry, but the **bleep** file has been a standard cut for my 85 years.
When did they change the file that has two cut angles as opposed to single cut for a mill file.
miata93
Instructor

When I first saw the title of this article, I thought that it was going to be about the Crescent adjustable wrench. There is a correct and incorrect orientation when torquing a bolt while using that wrench. To maintain the adjustment setting, the direction that the torque is applied should be on the solid non-adjustable side of the wrench. This ensures that the adjustment stays fixed and there is less chance of rounding the bolt.

As far as files are concerned: buy good files, work softer materials, keep them clean.
DUB6
Specialist

"There is a 50 percent chance you've been filing wrong" made you think it was about adjustable wrenches?  Hmmm.  I actually would have guessed maybe it was about arranging your folders alphabetically versus chronologically... 😋

miata93
Instructor

The email title that I got from Hagerty was:
"Are you using this tool the wrong way?"
I did not realize that it was only about files until I clicked further LOL.
TonyT
Technician

"Torque" and "Crescent Wrench" are mutually exclusive words.
miata93
Instructor

Been there !!

DAdams
Intermediate Driver

Just a thought. My reasoning may be totally off the wall, but it seems to be plausible. As a file cuts, the scrape creates a burr on the tooth. In the lift on back stroke method this burr will be torn away and replaced by a new burr on the subsequent cut, eventually dulling the file. In the back drag method this burr acts as a new tooth cutting material until it is torn away, effectively resharpening the tooth for the next cut.
DUB6
Specialist

   @DAdams - I would like to see scientific research to prove/disprove the theory, but your reasoning does indeed have a degree of plausibility to it - on paper, that is.

Rick2
Instructor

Anyone ever hear the one about before milling machines files were German milling machines?
F360Spider
Detailer

My favorite file is a die grinder. I find files more useful for deburring than for removing material. When I do file, I use the back and forth method. The more important tip is to attack the material at an angle instead of straight on.

 

cody6268
Pit Crew

The one thing I think most people who own files don't know is that they need maintenance and cleaning like well, basically any tool worth their salt. Those that aren't clean usually dull, and in my experience, old rusty files can't really be cleaned up. I have a massive Black Diamond I'm hoping I can make a decent knife out of.

A wire brush works in a pinch, but I recommend a good file cleaning card. I need to buy a new one. Mine's at least 50 years old, hand-me-down, and half shot. I have cheap Nicholson under Apex ownership, I have USA Nicholson (some of the best), Black Diamond, and even EXPENSIVE (but, I got them used) Swiss Grobet.
Buzz
Detailer

The same guys that lift the file and don’t back drag because it dulls your file are the same guys who don’t downshift at stoplights to save the clutch.
Back bragging helps me more evenly file as it creates a better feel for the material and more repetitious, consistent pressure and motion. It also depends on the substrate I am filing. I lift on softer material as each following stroke requires consideration as to pressure.
DUB6
Specialist

   Back in about 1974, I was taking a test drive with a safety manager in hopes of hiring on with a company as a long-haul driver.  I'd had a couple of years' experience, and figured it'd be a snap.  I was pulling an empty trailer, and he was telling me what to do - putting me through the paces, so-to-speak.  We were about 5 minutes into what he'd said was to be a half-hour test.  When he told me to exit the freeway, I downshifted the 13-speed through several gears while slowing down on the off ramp, then applied just enough brakes to stop at the end.  He chewed me out and said that was all wrong.  "Use only your brakes", he said, "transmissions are expensive to replace, but brakes are cheap".  I said, "I'd rather save my brakes than my transmission."  He laughed and said, "That's dumb - transmissions are more valuable than brakes."  To which I replied, "Not when I'm bearing down on an emergency with a full load - I won't care about the cost of a transmission then, but I'm gonna be glad I saved the brakes for when I really needed them - and so are you."  He told me to turn around and head back to the yard, he was satisfied that I had safety in mind.  😎

John
Intermediate Driver

I can see your point on an 80,000 pound truck. However, in normal daily driving I do not downshift and just use the brakes. Brake pads and shoes are cheaper and easier to replace than clutches.
Tazmanbdj
New Driver

I've got a '58 Bug and the brake shoes are real small even though they were enlarged from the '57 brakes as a "safety upgrade for the '58 model". All that said, the owner's manual teaches the new car owner how to downshift to compensate for the small brakes.
RG440
Instructor

Do yourself a favor and get a “Farmer File” You won’t look back ! Loose clothing around anything running is the #1 NO NO. The #2 is STAY AWAY FROM THE FILE TANG END! Being a machinist with a file is like the Marlboro Man with a cigarette. Handles come off inadvertently, handles can’t be found, handles the wrong size and so on. The farmers file has the handle built in along with the double bonus of a hole in the handle for hanging. They are the safest/best file I have ever owned. Nicholson is the industry leader in files (US) and one can be had for Under ten bucks,Your Welcome
johnmachiner
New Driver

There are several types of files, it appears like a second cut is being tested, which would cut in 2 directions, but a mill file or flat file most likely would not.
wickedace
Pit Crew

This sounds like an"which way the toilet paper roll should be placed in the holder" conversation. I was corrected as a young apprentice to cut and lift but later saw millwrights sliding the file both ways on steel. I asked and the answer was a shrug.
Lemans
Pit Crew

Reminds me of a funny story about buying tools for a job. I used to work for Delta Air Lines as a Technician and your first day on the job they would give you a tool list and on that list was a "Half Round File", well because the list was printed on a mimeogragh (before modern copiers), one of the other new technician from south Georgia thought the list said "Half Rough File", so he bought a new file and tried to make it Half Rough by hitting it with a chisel. The lead tech couldn't believe what he saw, he asked the tech, "what is this" and the tech responded, "a Half Rough File like it says on the list". Well the lead tech started hooting and hollering and called over the other Lead techs, everyone had a good laugh over it and the tech never lived it down (he didn't stay a tech very long). Thanks for reminding me of that event!
GRP_Photo
Instructor

One of the magazines to which my father subscribed (probably Popular Mechanics) in the 60s said (apparently correctly) that filing back and forth was the way to go. I took a jewelry class in '69 in which the instructor chastised me and said "not so." I did some experimentation with silver and discovered that the instructor was correct; working back and forth with silver clogs the file. I suspect that would be true with other soft metals (like brass).
I think the correct answer here is that it depends on the metal you want to file.
DUB6
Specialist

Correct that softer material clogs more.  Hence, when taught to use a wood rasp (essentially a file for really soft material), I was shown that back-dragging was necessary to remove what had just been caught by the teeth.  But I don't think it has any effect on dulling those teeth - nor do I think that stuff like aluminum or brass or silver or gold are hard enough to damage the teeth of a hardened steel file.

TG
Technician

Interesting piece, and very scientific approach, but I probably have 20 or more files squirreled away in my shop and can say with certainty that I will never dull one of them, let alone all of them, no matter how I use them
ConfuciusRacing
Detailer

So I ask: How many readers know what a "file card" is?

...the ones who do are in the 50% who file correctly.
DUB6
Specialist

@ConfuciusRacing - Card File?  They used to use them in the library, right?  😊

Scamersaxe
Pit Crew

I was always taught to cut on the forward stroke. Pulling it back against the metal, or wood, would damage the teeth. Just keep a file card handy to clean out the debris from the file.
clasact
New Driver

Well... I am not a machine!  I like to  get a cut flat and even.  If I were to  cut one direction/ forward only I will get a flat and even cut.  Using a two direction cut  there will be a rocking  motion and I will lose the  precision of finished  product I demand of my self.   Yes ..I use a file card and clean the file frequently depending on the  material  I am working with.  The slightest chip in the file and I get a scratch... which is UN-acceptable!

BPatLeMays
Intermediate Driver

I said: "huh.." when I saw this. I like the method of testing these guys did, kind of a "mythbusters" proof. I always worry about damaging my fine files, but I think I'll be less so now. My concern will be down force now.
jaysalserVW
Advanced Driver

While the demonstration MAY prove that the file is not damaged--there is something more at stake here. I shouldn't need to say this--well, should I? Sigh--I guess that I will, Kyle. It's called Strength. Answer the question which follows--be honest, now! Do you have more strength pushing or pulling the file? When pushing the file--teeth against the metal--prob. most of us will be able to bear down as we push. Bearing down while pulling the file will be more difficult--due to how our arms-muscles operate. It's a matter of how the body is built. Given that you and I are of similar build, and with files which are identical and the material to be cut is identical--I will be able to out-perform you with my file-push-cutting only. Hands-down. Try it! I read a study on this when I young (probably 50 years ago now)--the subjects were given files and told to cut a railroad rail using the files cutting one way and cutting using the file "cutting" by pushing/pulling both directions. Cutting by pushing the file according to the set of the teeth won the day. Thus--whether or not the file is damaged by pulling never was the question I asked myself.
SAG
Technician

I have a tool box drawer full of 'metal files',
no mystery here
NHO
Intermediate Driver

If I need to make a heavy cut I've always pushed a file ahead hard. To make a light cut, I pull it back. Always worked for me in my 7 decades on this earth.
ThumperUSMC
Intermediate Driver

I have used files in both directions for almost 60 years and have never damaged a file to any noticeable extent, although I have worn out more than a few over the years. My "Big Secret" has been to always use a good file card after a few strokes to clear the file. My filing has been on both steel and aluminum in the course of my work. I DO use a different set of files when working on the different metals though to prevent contamination through "osmosis" of the materials as aluminum and steel do NOT get along and putting the two together will cause corrosion at that area. Corrosion IS your enemy when it comes to metals. The video was great. I only wish my skills could match the machine...LOL