Know Your Accessories : The Bastard File

Not a glamorous tool, but a darned handy one to have for rough sharpening tasks.

The humble bastard file might not win any awards for beauty or innovation, but mine has been a workhorse over many years. Bastard files fall in between “Coarse” and “Second-Cut” or Finishing files on the coarseness scale. They are most commonly used when a moderate amount of material must be removed , and the appearance of tool marks on the workpiece is of secondary importance.

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The square of cardboard is an old scout trick to protect your fingers from the sharpened edge.

A bastard file can be used for any task where one wishes to remove metal without sparks or with greater control than is possible with an electric grinder. I used mine extensively in the building of my Jeep, especially when refinishing the axles. Most often though, I turn to it for sharpening axes, machetes, and lawnmower blades.

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Using my left hand as a guide/support as I sharpen the flat underside of a mover blade.

With all manner of electrified tools at our disposal, it is temptimg to pass on the hand tools. While I could use a hand-grinder, bench grinder, or belt sander to sharpen the above-mentioned utilitarian blades, it is usually faster to just clamp them in the vise and grab the file. (this often holds true when woodworking as well. You can often take 5x as long to set up a machine as simply grabbing a hand saw.)

I had my file out on Friday when I determined that my mower blades had passed the point of being “sub-optimal”. In fact it looked like I was mowing with a team of goats. It took on average 4 minutes to adequately resharpen each of the 2 edges on the pair of blades.

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The passes on the right were made with the dull blades. The mower bogged down repeatedly in the tall, wet grass. 20 minutes of sharpening and the results (left-most pass) were much better.

Visit EvenfallStudios for a wonderful and thorough guide to anything you ever wanted to know about files. Really an informative page.



  1. I know that this is not the most exciting topic on the planet. However, I really do encourage you to check out the EvenFall Studios link. Incredibly informative.

    What else do you all use to sharpen your outdoor edged tools? (Axes, Machetes, Mower Blades and the like)

  2. Marmot says:

    I was a Scout for many years and never learned that cardboard trick. I’ll use it from now on. Thanks. I’m going to try using the round Gransfors Bruk sharpening stone I bought with my new Small Forest Axe on the lawn mower blade. It will make an interesting comparison to the usual bastard file results.

    1. It is a simple little thing to do (stab the tang through a cardboard square before inserting the tang in the handle). But it works. Saves your knuckles from a slip up.

  3. Raina Collins says:

    I use a combo wet and dry grinder from Harbor Freight, a giant old two grit sharpening stone, and finish with the coarse stone from my old Case knives set. For a customer, I’m willing to mirror polish with progressive grits. You can shave with my axes. 🙂

  4. knightofbob says:

    During my stint as a wildland firefighter, I found the raker files from the saw kits could get an axe shaving sharp during a lunch break. Not that you really needed to keep the axes that sharp, but I did. I could usually limb a pine with a sharp axe faster than most with a saw, but guess which one of us was winded at the end?

  5. Matt in FL says:

    My dad always used (and taught me to use) the bench grinder for the lawnmower blade, but the machete was always sharpened with a file. Long, smooth strokes, and it’d eat up the banana trees in the corner of our back yard like cutting through air.

    1. I have certainly used the bench grinder on mower blades, but it would have taken me longer to sweep up any nearby sawdust (fire is bad m-kay?) than it took to just hit them with the file.

  6. gunfighter 2012 says:

    Shenanigans! I officially call Shenanigans. Unless you are sharpening your lawnmower blades every day, I say it takes a good bench grinder or sander to properly sharpen a set of blades. And unless your willing to come to my house, sharpen my blades aaaaaand mow my lawn. I don’t believe you.
    So there.

    1. Really? There was enough sawdust on and around my bench (my son dumps sawdust out and plays with his diggers) that I didn’t want to take the time to sweep it all up just to sharpen the blades. The sparks are too much in a wooden shop unless I take the time to clean first.

      I actually think the grinder is too aggressive if one is not careful as well.

      One may disagree as to the relative effectiveness of a bastard file, but I assure you my pictures and description are accurate to my experience both at the time of my writing and historically.

      Thanks for reading.


    2. sorry, I missed some of your levity the first time around. My response seemed over defensive.

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Know Your Accessories : The Bastard File

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