Introduction to Files and Rasps




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This is a basic introduction on proper use and care of files and rasps. Here we examine a number of different sizes and shapes of files and rasps.

When sawing and drilling, you create burrs and sharp edges on your workpiece that need to be removed; rasps and files take care of these. Using a rasp or a file is often the first step in finishing a project, or prepping a material for the next step.

Step 1: Identifying Files and Rasps

A short (non-comprehensive) list of files, as pictured below from left to right:

Flat rasp - has large, coarse teeth to quickly remove material
Flat file without a handle - allows you to remove burrs and rough edges
Multi-use rasp and file - has two files and two rasps on one tool
Fine flat file without handle - this tool is for finishing and scratch and gouge removal
Triangle file - allows you to get into corners and clean up edges that have notches
Small round file - cleans small round holes and inside curves
Medium round file - as above, but with coarser teeth
Large round file - as above, but coarser still

For more information:
Wikipedia Rasp Entry
Wikipedia File Entry

Briefly, a file is for detail work while a rasp removes larger quantities of material.

Step 2: Using a File or Rasp

Push the file in one direction only. Remember, it' s not a saw -- this file was meant to cut on the away stroke. Put pressure on the return stroke and you'll dull the file and mangle the cutting edges.

Here, Lynne is filing out the corner of a sign she cut on the plasma cutter. Since she's filing out both sides of the corner, she can butt the file up to both edges. In this situation, you could also use a triangle file to smooth the corner. (She's trying to smooth out a pit from the plasma cutter's piercing move... but that's a different instructable.)

Step 3: Cleaning Files and Rasps

Finally, once you're done, make sure to clean the file. For light work, you can use a file card or wire brush to flick out the metal chips caught in the file's teeth. In this case, the aluminum chips are practically welded to the file, so we've got to resort to tougher stuff. In the ensuing photos, Lynne takes this file to a bench grinder (using the wire wheel). Even so, this file might be done for.



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    28 Discussions


    4 years ago on Introduction

    I would advise never to use a file card for cleaning a file, and definitely not a wire wheel, the steel bristles will ruin a good file quite quickly. If you have a file loaded with aluminum then a quick soak in sodium hydroxide will at least loosen the aluminum enough to remove it with a sharp wedge of wood or brass/copper.


    4 years ago on Step 3

    Almost forgot, a piece of Bamboo cut as flat as possible works almost as good as a copper scraper too. On some files it woks better, like the round tapered variety. In both cases (using copper or Bamboo) Just rub in the same angled direction as the the file grain. You will be amazed with the outcome because it is quick & painless & works 100%.


    4 years ago on Step 3

    A flat copper scraper (made from old cooper pipe opened with tin snips & flattened on one end)works best to clean aluminum & other stubborn Gunk from a file. Also if you are filing aluminum rub an old candle on the file first. Some say use chalk, but your ordinary every day candle wax works better.


    5 years ago on Step 3

    When I've utterly mangled a single file, I usually go in there with a spare scriber (etching tool) I have lying around. With enough patience it can clean the grooves of debris pretty thoroughly.


    10 years ago on Step 3

    Hi! I heard from an old friend, an engineer, that the best way to effectively clean a files is to immerse it in hydrochloric acid. Thereby, the bits and pieces stuck in between the file teeth will either be eaten away by the acid or slowly be dislodged as the acid gradually eats away at the iron filings. Though, I really haven't tried this method because, I dislike the risk of burning myself with acid and finding a place where to dispose of it when I am done.

    2 replies

    Reply 5 years ago on Introduction

    Just found this ible, glad I did!

    I used Muriatic acid, and it cleaned the files up quickly!


    Reply 9 years ago on Introduction

    Yes, I have heard of using battery acid (if you have an old battery around).  But keeping it a little longer in muriatic acid (it is a moderately dilute hydrochloric acid used for cleaning concrete and 'shocking' swimming pools), or even in chlorine bleach (it again is even a weaker hydrochloric acid).  The weaker just takes longer. 

    Once you get them out of the 'acid bath', rinse it off with water to get the acid off.  If it seems sharper, it is working.

    If it doesn't seem sharp enough, then like the shampoo bottle says, 'rinse, repeat'.  I have heard of having to do this several time (3 to 6) depending on the initial shape of the rasp. 

    If it is 'sharp enough', put a light coat of oil (like WD40 or similar) just to help keep the rust away.  If you don't protect from rust, rust will attack pretty quickly.

    And noting will fix mechanically broken teeth on a rasp or file.  They are quality tools and should not be stored in coffee cans where they bang against other tools without protection (ok, soap box here, but you get the idea).


    6 years ago on Step 3

    pennies are no longer 100% copper - in fact they have zinc.

    The link has a table that gives the % of zinc based on each year's production.


    Another trick is to use sidewalk chalk, just run the file over the chalk to load the teeth area with a fine coating of chalk.  After you are done filing, the wire file card (cleaning tool) with flick the metal filings out as the chalk layer separates easily. 
    This works well with aluminum, and plastics.  For files used in metal only, a pre-coat of WD-40 is a handy way to aid cleaning, and to keep the file rust free.

    Don't drag the file backwards, it ruins the cutting edge, and remember, don't press hard, the cutting edges do the work faster with a light pressure as the multiple edges each take a fine cut rather then trying to scrape off huge amounts with just a few teeth.

    3 replies

    Sidewalk chalk is a great method, as is welder's soap stone, and I've heard of people using soap, though I wouldn't recommend it. As for WD-40, I wouldn't use that since it will cause fine metal dust to cling to the niches in the file.

    The "oil" in WD-40 is a fish oil derivative that inhibits rust. The oil is very fine and will hold only the most minute of particles. The next time the file is used, the vibration will break the small particles free, The use of a small wire brush like a 'file card' (available at most hardware stores) will keep the file clean and clog free.

    The file cards are minor tool miracles when it comes to prolonging the life of a file. I've just had issues with bits staying in the grooves/divots of files I've used oils on (including WD-40).


    7 years ago on Introduction

    My "trick" for old, rusty or dull files is to clean them in a bath of vinegar. I use an small mapp gas can (similar in size to the tall propane cans used for small torches) with the neck cut off. I stand the files up in the can and then fill with vinegar. After they've soaked over night, the rust has either flaked off or will easily rub off in bag/box of kitty litter or vermiculite.
    Files that have been totally used up or with too many broken teeth, become awls, scribes, or specialty blades. With some tempering, they make very good knife blades.
    Great instructable.


    7 years ago on Introduction

    A easy way to clean files at


    9 years ago on Introduction

    Thank you for posting this.  In a former life, I taught a Sophomore Mechanical Engineering Design Lab at the University of North Carolina at Charlotte.  Teaching these students that a file only works in one direction and you ruin a file by using a sawing action was a tough sell.  However when they saw the results you get with so much less effort by using a file correctly, they were instant converts.  Its nice to see such advice "in the wild" as it were.


    9 years ago on Step 3

    Jacaroo says:
    Excellent presentation, take it from someone who has used files and made them unusable.
    My dear departed Dad made me sit and clean each one of his files with a piece of Brass which was run along the grooves  and this dipensed of anything from lead to aluminium and other soft metals, it even removed rust if enough elbow grease was applied.
    You see Dad was a Seargent Major and a Master Technician


    10 years ago on Step 3

    My grandfather believed one of the most useful things to have in the workshop was a load of candles. Rubbing a woodscrew on one would make it go in easier, on a saw would make it get caught less, and on a file it would make it easier to clean afterward.

    3 replies

    Reply 10 years ago on Step 3

    Your grandfather sounds like he was a wise man. I still use this trick today. My grandfather told me keeping pennies in your toolbox helps prevent rust. Whether this was ever true (in the days they were made of copper) or not, I don't know, but I still keep a couple of pennies in each of my toolbox drawers as a sort of tribute to the old man's esoteric wisdom. ;-)


    Reply 10 years ago on Step 3

    Well there might be some sort of galvanic/sacrificial-anode chemistry to back it up, like in boats, but would have thought it'd work best with nickel or zinc coins. So maybe he heard it from someone in the USA? The only other mote of wisdom that springs to mind was to place a small square of cloth between the drill bit and metal when drilling through a sheet to prevent it chattering and making a ragged hole. Seems to work, though I'm unsure if the cloth needs to be oiled or not for it to.

    My mom kept a sacrificial galvanic plate in her silver ware box to keep the tarnish down. ... I don't see why the same principle would not work in a tool box.

    I don't remember my chemistry, but if copper is more chemically active than iron, then keeping a couple of pennies (outside is still a good copper plating) in a drawer should work.

    If the pennies get to oxidized, replacing them (or polishing the old ones - but no oil covering or anything to keep the oxidation off, the oxidation on the copper is what is helping, by keep the other metals from oxidizing.

    Also the little bags of water absorbing material helps.  Those can be 'recharged' in a toaster oven by raising the temperature to a little above 100C or 212F for a while (an hour or so to just above the boiling point of water ).  It should drive off the moisture and let it absorb more.  Doing this regularly (very few months) can help too.  Let them cool and toss them back into the drawers!