Plane Soles: Ham Hands Make Iron Bananas

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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