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While teaching a class on handplanes this weekend, one student in particular was having a heck of a time with his Veritas No. 4-1/2 smoothing plane. Let’s call him Mr. Papanicolaou. (I just hate it when writers use simple names for pseudonyms.)

Papanicolaou was trying to dress a board with the plane, but the plane refused to take a consistent cut. The plane would take a shaving at the beginning of the board, but then it would kinda crap out somewhere in the middle.

And so began our diagnosis.

First we checked to make sure the frog was secured tightly to the plane’s body. Check.

Then I looked at the board to make sure it wasn’t springing between the bench dogs. Check.

Then I checked his mechanical adjuster to see if there was any backlash in the mechanism that was fouling him up. Nope.

Then we reassembled the entire plane. I checked the sharpness and shape of the iron (check and check). We reattached the chipbreaker and made sure it wasn’t bending the iron off the frog.

We checked the tension on his lever cap to make sure it was holding the cutter assembly against the frog.

Then I took some shavings with the plane myself on my workbench and on a board I knew to be flat. Perhaps Papanicolaou was applying pressure at the wrong places. Perhaps the bench had a bad hollow. Perhaps the board was just wacky on the junk.

I had the same problems as Papanicolaou.

And that’s when I turned my attention to the sole of the plane. I didn’t have any feeler gauges, so I checked the sole using a straightedge and held the plane up to the light. Sometimes this method exaggerates the problem because you see the light reflected off the sole , effectively doubling the error.

But the problem leaped out and poked me in the eye. The sole was the shape of a malformed banana. There was a large bump right behind the mouth. And another smaller bump at the heel. (The photos are of the plane taken in front of a tracing box.)

In this photo the plane is rocked forward on the bump behind the mouth so the toe is touching. This plane rocks!

Papanicolaou sheepishly volunteered that he’d flattened the plane’s sole to try to increase the performance of the tool. Now we had our answer.

This isn’t the first time this has happened during a class. And so here’s my advice: If you spent serious money on a tool, don’t flatten the sole yourself. If you suspect you have a problem, call the manufacturer for advice. If there’s a problem, they can fix it for you.

If you are buying old tools, take a straightedge and feeler gauges with you. Check the sole of the planes you are interested in buying. You need the areas in front of the mouth and along the sidewalls to be coplanar (a hollow area in the middle of the sole behind the mouth is usually OK). If you find problems that are more than .004″ in critical areas, be wary.

If you do decide to flatten the sole of a plane, practice on a junker first and read up on the various techniques on the Internet. Here’s what I do: I glue a long strip of blue belt-sander paper to granite. I can flatten block planes, smoothers and jack planes with this setup. Jointer planes are a bear.

Not all your planes need to be dead flat (anything used for roughing can be wonky). But if you want to take really fine shavings, it’s important.

– Christopher Schwarz

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Showing 16 comments
  • Tracy Luegge

    Wacky on the junk… I nearly peed my pants when I read that!
    Wacky indeed Mr. Schwarz, on the junk or otherwise.

  • bugbear

    I have written extensively (obsessively) on this; my page is quite large, and has many links.


    P.S. I need a new host, since yahho are aborting geocities

  • skip

    Thanks BubBear for sharing some very detailed article; I’m going to bookmark them for future reference (so I hope Yahoo will have forwarding links). I have to say, however, that I’ve never had to go to quite those lengths to get an acceptably flat sole.

    That’s a great suggestion, Ron, for using blue Locktite on the hold-down screw. On the LN rabbetting block plane, I’ve tried marking the tensioning wheel itself, but I don’t seem to be able to remember how many turns (and from what starting point) are needed to put the exact same amount of tenion on the blade (and hence the sole). Lock-tite on the portion of the screw where it enters the casting of the cap might provide a better reference. I’ll give that a try. Thanks Ron.

  • Ron Hock

    A dab of blue Loctite on an Stanley-type plane’s hold-down screw will secure its adjustment (and is still re-adjustable, but much harder to turn) so that the lever cap will snap with the same pressure each time. Don’t use the red Loctite — it’s bond it permanent unless heated.

    (This tip came to me from Brian Burns, guitar maker, tool designer and author of _Double Bevel Sharpening_.)

  • Adrian

    Is the problem that the supporting surface isn’t flat…or is it an inherent problem with the idea of flattening by abrasion? Sort of like the way that if you plane a board you’ll likely end up with a convex surface. Some people insist that the only way to get a flat surface is by testing the sole against a flat reference coated with dye and scraping off the high spots.

    Charlesworth says that you have to flatten shoulder planes with the blade tension set to a known level. He says to put a mark on the tension knob so that you can set it consistently. I suppose something like this might work for a bevel up plane if you’re very consistent about how you turn the screw (or if you never turn the screw, only the tension knob).

  • Skip

    I guess it’s a matter of how flat is flat. I’ve flattened dozens of soles on Stanley, LN, Clifton, Record and other metal planes over the years and never ran into a problem except in two instances (more on that in a minute). The secret is making sure the backing for whatever abrasive medium is used is truly flat (or darn close — within a thousandth or two). Glass is not always flat, particularly if it has been used previously a granular abrasive (glass wears, like anything else). Machined steel is good; granite is better. Where I have had trouble is in flattening the soles of the LN rabbeting block plane and the low angle jack — for precisely the issue that Ron Hock alludes to. The issue is how much tension to put on the blade. These soles, because of the design, can deflect. In fact, a half a turn of the tension screw can change the configuration of the sole. Everytime you remove or even adjust the blade it’s almost impossible the get the same amount of tension back. Anybody out there got a magic suggestion keeping these soles flat?

  • Adrian

    I attempted to flatten my first bench plane, an ebay #5, with the blade installed using sand paper on glass. I don’t think it was great before my effort but afterwords it was definitely considerably worse. I gave up and bought Veritas instead.

    I’ve observed the same problem in flattening water stones: they end up humped instead of flat.

  • Bill

    Thanks for your candor. I’ve always wondered why I pay top dollar for a Lie-Nielson and then have to flatten the sole. What am I paying for? I have flattend my wooden smoothing planes that I picked up, always with the blade in it. But have not had to flatten any of my Sargents, Stanleys or Lie-Nielson. Now I don’t feel like I’m not caring for my planes by messing with the sole which appear flat. It ain’t broke, I’m going back to messing my unfinished projects. I have got to finish my light box made out of pvc, now there is something you shouldn’t cut with a chop saw kind of like bamboo.

  • Mark Wells

    I tried flattening a wooden plane with sandpaper on glass and got the same banana. One of the things on my to do list is to try BugBear’s method:

    Clark & Williams say you can use the same "print & cut" method by using carbon paper or blue chalk as the ink.

  • Matt Wilson

    Papanicolaou? are you kidding? I think you should stick with a simpler name than that of the inventor of the PAP smear…

  • Dave Anderson NH

    Hi Chris,

    I’m a firm believer in the olde adage of if it ain’t broke, don’t fix it. Any addition to my shop of old planes gets a test drive before any work is done. Believe it or not, this includes sharpening and honing the iron. A cosmetic cleaning with an old toothbrush and some mineral spirits after a quick disassembly is next. Finally I’ll remove any rust, squirt on some Top Cote and buff it up, and sharpen and hone the blade.

    I’ve always felt that if you take care in what you purchase the old owner probably had the plane working pretty well and the less you do the better. But then again, I’m not one to get an old plane all shiny and new looking with fresh paint or japanning either.


    Best regards,

    Dave Anderson
    Chester, NH

  • Christopher Schwarz

    No, he didn’t. If I have a follow-up with him, I’ll ask.


  • JC

    did he mention the method he used to try and flatten the sole?

  • Ron Hock

    Hi Chris,

    When flattening the sole it’s important to have the blade in place (but retracted!) and under normal-use compression. This is especially the case with wedged wooden planes but applies to metal planes as well. The pressure applied by the lever cap presses the front of the frog against the sole, creating a slight, but real, bulge. If you flatten without the blade in place, this bulge will appear when you re-install the blade and all bets are off. I’m guessing Mr. Papanicolaou flattened his plane with the blade sitting on the bench.

    Here’s a photo of the guts of a cut-away Stanley plane: that may help illustrate the situation.

  • Amos

    I did the same thing as Mr. Pani. I did a lot of reading from many sources on plane fettling before I bought a flea market plane and "flattened" its sole. I was proud of myself for doing the research and putting alot of time into sole flattening. Of course the sole ended up resembling a warped banana. NONE of the literature I read mentioned this risk, so thanks for putting this out Chris!

  • Turner

    Excellent analysis. I’m printing this one off.

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