Chris Schwarz's Blog

Why I File the Corners of my Irons

Before

After

When setting up bench planes, the enemy is plane tracks – the ugly step created on a board when one (or both) of the corners of the tool’s cutter digs into your work.

In my opinion, plane tracks are uglier than tear-out, rotary-cut plywood and a Cincinnati Three-way.

There are lots of ways to avoid plane tracks. You can sharpen a slight camber in your cutter. You can sand out the plane tracks. You can do magic tricks. (Some woodworkers manage to use straight irons with good results.
– Ron Brese and Deneb Puchalski are two guys you can bug about this.)

Years ago, before I started cambering my irons, I merely filed the corners of the cutters so they were a small radius. This greatly reduced the chance that a corner would dig in.

I still file the corners of the irons for my bench planes. Here’s why: If the problem is caused by the corners, then remove the corners. Even with a cambered iron, the corners can dig in if the blade is set for a deep cut or it is not perfectly aligned in the mouth of your bench plane.

So if you file away the corner, the worst thing that can happen is that you will get some plane tracks with scalloped edges. And that looks much better than the sharp arris caused by an unfiled corner.

It takes just a minute to do. Here’s how it works.

Before you hone the iron, place it on a work surface – I usually use a scrap of wood. Place the iron so the bevel is facing down.

Get a file, almost any file. I use a mill bastard or a Multicut file because that is what is in my drawer.

With one hand, press the iron down. With the other hand, hold the file on its edge and against the side of the iron. Push the file forward and swing it around the corner of the iron until it is parallel to the edge of the tool. Do this a few times until the corner looks radiused.

This will bring up a burr on both the bevel and the face of the iron (which is why you do this before honing).

Switch hands and repeat the process for the other corner. Then hone the iron.

The short movie below shows what the hand motions look like. You can also do this process on a disc sander or belt sander. But a file is less likely to mangle you.

— Christopher Schwarz

Other Sharpening Stuff
• Do you have Ron Hock’s new book “The Perfect Edge” yet? You should. Ron has taken an esoteric topic and transformed it into some thing that is fun to read. Everyone needs a book on sharpening. And this is a very good one.

• Another excellent sharpening resource is Ian Kirby’s DVD “Sharpening Planes & Chisels.” Check it out here.

• For sharpening equipment, you should check out the site SharpeningSupplies.com. The company has a wide range of goods for every kind of sharpener.

• Having trouble sharpening scrapers? Check out this free story I wrote on our web site.

13 thoughts on “Why I File the Corners of my Irons

  1. Tom Holloway

    If I remember correctly, Frank Klausz has been advocating this detail for some time now, for similar reasons. The technique you show in the video looks (and sounds) a little rougher than what I want to do to the iron of a smoother when close to final honing. I use Scary Sharp, and the way I relieve the corners, at the stage close to final honing, is to go back up my marble SS plate to, say, 150 grit, and gently swipe the corners a few times on the edge of the patch of sandpaper, at a somewhat steeper angle than the main bevel. I then quickly move back down the grits ending up with a corner relief that is both gentle and smooth. However it’s done, it’s good to do.

  2. PAUL

    Chris,
    In Arkansas, twas called Spagetti-red. Made by my bride, using her fathers "German chile recipe" it was to die for Literally!

  3. Ed Furlong

    Chris:

    Thanks for the video–it really clarified the process in my mind. For some reason I was having a hard time visualizing how the procedure worked.

    Perhaps you can video a Cincinnati three-way for the community, and provide similar clarity, or are there laws against that in Ohio? I suppose you could always go to Covington.

    Ed

  4. Christopher Schwarz

    What is most disturbing is to hear a creepy old dude order this: A child’s four-way.

  5. Christopher Schwarz

    The rounded over corners do get sharp after some finger pressure — especially on the unbeveled face.

    However, what’s important is that if that area digs in to the work, the result isn’t disaster — it’s a rounded shape instead of an arris.

    Hope this makes sense.

  6. Charles Davis

    From what I read it seems that your current practice is to both file the edges of and camber your plane blades. Did I read that correctly? If so, do you add the camber as you just prefer a slightly radiused cut to a flat one, or is there some other benefit?

    I did google the Cincinnati three-way (somehow my search bar already had the "three-way" part in there). Pasta and chilli together???? My mother would slap the Italian out of me if I ever made such a thing. I am impressed that the boldness does not stop at a three-way and that you in fact can progress up to as far as a five-way, legally.

  7. Chris G

    I’ve always cambered with finger pressure, but haven’t ever tried clipping the corners, so please forgive me if this is a stupid question. Once you clip the corner do those rounded over areas stay blunt or do you hone them sharp using finger pressure? I realize that if you set the iron light enough the blunted corners won’t hit the surface anyway (just like a cambered iron), but if you set the iron two deep won’t there be some dull/blunted areas that end up marring your work??? Am I missing something??? I’ve been curious about this for a while, because this is something I want to try doing.

    Also, the main reason I’m intrigued by filing the corners is that I’ve always imagined that this would allow you to get a shaving the is more uniform across its width, when taking a really thin cut(because less camber would be required). Is this in fact the case?

  8. Christopher Schwarz

    That works brilliantly, too. That’s the way I did it at WIA when I left my file at home.

    In that case, I moved the iron across the stone.

Comments are closed.