Chris Schwarz's Blog

Super-specific Smoothing Plane Specs

When I teach people how to sharpen and set up a handplane, I can jabber endlessly to little effect. Sure, I’ll get in a few jokes about lemurs and frogs (and their forbidden love), but I really don’t earn my keep until I start the “show and tell” section of the lecture.

That’s when I take apart each of my handplanes and pass the individual parts around. The students can see how curved the iron is. They can observe how tight the mouth is. And, later at the bench, they can pick the tool up and see how well it works.

When you write about handplanes for a living, it’s difficult to pass around the parts of your planes to your 200,000 readers. So today I’m going to take apart a plane that works extraordinarily well and try to describe its features using measurements that you can use.

About the Plane
If all my handplanes were repossessed and I had time to stuff just one in my pants (believe me there’s room. See this photo from Popular Woodworking for proof. My wife has offered to buy me implants for my birthday.) before the repo man came through the door, it would be the above plane.

It’s the Lie-Nielsen No. 4 in bronze with a 50Ã?° frog. I have more miles on this plane than any other, and I have it set up exactly how I like it.

How do I like it? Let’s see:

The Curve of the Iron
I like a smoothing plane’s iron to have a slight camber. This curve keeps the corners of the iron from digging gutters into your work, and it produces a beautiful finished surface that has a subtle undulation. How much curve?

That’s the problem. If the curve is too pronounced, you’ll take a very narrow, thin shaving at the middle of the mouth. If the curve is too flat, the corners will dig in.

There are math formulas that tell you how much curve you need , it varies depending on the width of the blade and the angle of the plane’s bed. For this plane with a 2″-wide iron, I like to get a shaving that is a little more than 1″ wide, .001″ thick and tapers to lace at the edges. That is what is shown in the mouth of the tool above. That’s a good shaving for general work.

I could describe the curve in terms of its radius (40′ feet perhaps), but that’s not helpful. Instead, I measured how much the corners of the iron were swept away at the edges of the iron. I did this by placing the iron against a square and measuring the gap with a feeler gauge (it’s just like checking the gap on your spark plugs).

On this plane, the corners were swept back by .006″.

The Chipbreaker
Two things are important about the chipbreaker. One: I keep it about 3/64″ from the cutting edge and I keep it fairly polished. I’ve written a lot about breakers, so I won’t bore you here. This setting prevents the tool from clogging and provides efficient shaving ejection.

I polish my breakers with a Klingspor hand block. The hand block removes the gunk that builds up on the breakers and polishes the bevel of the breaker. You can use sandpaper, too. Anything abrasive (except, perhaps, your personality).

The Mouth
I actually thought my mouth was tighter than this. When I measured it with feeler gauges it was .009″. I’m going to try to close it up just a little more. Sometimes the mouth will get changed when I disassemble the tool and demonstrate how the frog moves.

The one thing I cannot demonstrate here that it is really important is how much pressure is applied by the lever cap. It’s probably less pressure than you think. If I had to guess, it’s about the same amount of pressure you apply to open a typical car door.

However, as someone who owns an old Volkswagen that requires a Kung-Fu Grip to get into, that’s really not all that helpful.

– Christopher Schwarz

6 thoughts on “Super-specific Smoothing Plane Specs

  1. Auguste Gusteau

    Yes, there is a formula to find the radius of a circle knowing the height and width of one of its arc, but you probably do not know it, because if the width is 2 "and the height is 0.006", the radius is about 7 ft and not 40 feet as you wrote.

  2. Christopher Schwarz

    Jeff,

    What you are seeing there is not a Sharpie mark. It’s a feeler gauge that I’m using to test the camber. I’m doing this for the photo only. I usually just judge the camber by eye.

    Chris

  3. Jeff Hand

    Chris,

    Thanks for the reference numbers. I generally get good results with my eye-balled setting for the mouth but it’s nice to have something for comparison.

    Is your square in the picture with the iron modified or have a sharpie mark on it? I’m wondering it if that helps visually judge the camber.

  4. Rob @ Evenfall Studios

    Hi Chris,

    I recall you saying you have been fooling with Volkswagens for years.

    Well, the Volkswagen is a relatively simple car, most will agree. The dirty little secret of German engineering is in the door handle. They are a marvel of moving parts in motion. There is more going on inside a Volkswagen door handle than the the inner working of a clock, and you can bet it’s 16 digit part number on it. 🙂

    In a world where tight plus a quarter turn is the norm, thanks for mentioning the lever cap tension, thanks for sharing with folks what it should "feel" like.

  5. Sharon Lev

    Thanks Chris,

    for years I struggled with the amount of pressure to put on the cap iron myself.

    I eventually found a nice reference regarding the cap iron on Lee-Valley’s site. They suggest to turn the screw 1/4 turn after it contacts the cap iron – I find that setting to work very well, don’t need a gym workout to lock/unlock the blade, and it’s tight enough to hold the blade in place, and allow for very easy lateral, and depth adjustment.

  6. dave brown

    Nice tips Chris. When I’m tightening my lever cap, I like it where twisting the lever cap from side takes some effort. Sometimes I get it too lose and I can pull the lever cap off without flipping the cam so I just tighten the screw 1/8 of a turn and call it good. 😉

Comments are closed.