Kanna Workshop – Intro

I’ve been talking with some friends lately about teaching some classes in the future, some of which will likely take place in the States and focus on Japanese timber framing. Those discussions have got me thinking about a few other topics that I’d like to teach, with one being the use of Japanese planes, kanna 鉋. Almost everything in traditional Japanese woodwork gets finished planed, so using kanna is a crucial skill to develop. How to set up a kanna and sharpen the blade are important topics that can’t be ignored, but some of the details on using the tools and dealing with tricky situations are somewhat less commonly covered.

So I started writing down a quick list of the challenging areas that pop up when using kanna, as well as the areas that have to be addresses during use such as maintenance of the dai. What started as a series of quick notes ended up as 4 pages of bulletpoints. While I’d love to teach all this material in a class someday, in the meantime I thought I’d start a little series here on the blog and hopefully it will become a helpful resource to those of you using kanna.

To start things off I thought I’d simply share my list of bullet points, and in future posts elaborate on specific areas in more detail. I’ll probably update/edit this list over time, but I’m also totally open to suggestions so feel free to let me know if there’s something I missed, or if there are any areas of particular interest. The first portion is focused on kanna setup and adjustments, while the latter is geared more towards issues that pop up when using kanna.

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Sharpening

• Nothing solves problems like a sharp blade.
  • Many issues come down to a poorly sharpened blade.

Kanna Setup/Adjustments

• Dai/blade fit
  • Blade tightness and most important points of contact between the blade and dai
    • Must be careful not to be too tight, especially in the middle
    • When pushing in the blade it should seat evenly relative to the throat opening and not shift to one side or the other
    • Should be able to push the blade within a couple millimeters of the throat by hand
• Dai adjustment
  • 2 points of contact easiest to maintain and commonly used for most work
  • 3 points of contact can prevent the plane from digging into the stock towards the end
  • 4 points for joining/special situations
  • Hollow should be deeper towards the “tail” of the plane (the end closest to you when planing) and gradually sloping towards the blade
  • For finishing work the level of hollow is very slight; just a sliver of light when checking with a straightedge
• Adjustment tools
  • Dai-naoshi-ganna – great for a non-sandpaper method, and can be used with the blade protruding
    • Harder to eliminate twist
  • Glass plate/Sandpaper – Great for eliminating twist and ensuring a very even surface
    • Need to pull blade out enough to safely sand
    • Must blow of sanding dust/grit after 
    • Sanding with blade retracked means you may need to touchup with dai-naoshi-ganna after tapping in blade
      • especially behind the blade
  • Scraper – great for touchups while planing.
    • Easier to use than dai-naoshi-ganna, when it comes to quick touchups
    • Not ideal for dealing with twist or flattening the sole, but great for maintaining the hollow
    • Cool DIY scrapers can be made using wood holder and store bought razor blades
  • Straight edge – an absolute necessity for keeping an eye on the state of the dai
    • Best with a notch to allow use with the blade protruding
  • Hammer for tapping in/adjust blade and chipbreaker
    • Steel – will crown the blade and mar the surface
    • Wood – great for maintaining a clean blade but less inertia means it can be harder to make fine adjustments
    • Copper or Brass = good compromise – less severe on blade than steel, but still can potentially mar the surface, definitely better feedback when tapping and making adjustments
      • Copper is really soft and will mushroom

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Planing and Potential Issues

• Planing beam/bench needs to not flex and be flat
  • Also needs to be clean and free of grit/glue drips/etc. – anything that can damage and marr a planed surface or interfere with planing
  • Can be a finely made bench or beam, but can also be a simple post/beam/slab of wood – just needs to be flat and not flex relative to the task at hand
    • Narrow beams work great and can make it easier to deal with wide panels that may be cupped
• Get creative with planing stops
  • With any stops must be careful about the path of the kanna so as not to damage blade
  • Screws work great and are super simple
    • Bite into the wood making it easier to hold down bent or curved stock
    • Can only be used when the end of the piece will not be seen or will be cut off
    • Damage the bench/beam
  • Alternative to screws are Benchcrafted or Crucible planing stops
    • Bite into the wood the same way a screw stop does
  • Wood stops screwed or joined to the bench work great
    • do no damage to the material being planed
    • But less effective at holding stock that may be bent; nothing to bite into the wood
  • Clamps/wood blocking
    • Need plenty of space/clearance to avoid bumping into bulky clamps
• Dealing with bent/warped/curved stock
  • Screw stops are really helpful to hold down one end when planing with the crown down
  • Simple shims like rulers, or thin strips of wood can be helpful when planing crown up
  • For curved panels (across the width) a narrow planing beam can be helpful, follow by shifting the piece across the panel as you plane
  • In really difficult situations water can be used to adjust a panel
    • Can potentially exacerbate the situation
• Reading the grain
  • For flatsawn boards look at endgrain and direction of “cathedrals” to determine the grain direction
  • In tricky situations study the rays or cells and see which direction they are going
    • Sometimes grain lines are misleading, but rays and cells tend to tell the truth
  • Sometimes reversing grain/planing against the grain can’t be avoided
    • Make sure chipbreaker is setup well
• Dealing with tearout
  • Ensure the chipbreaker is setup well
    • Ensure even contact with the main blade; both need to be flat and mated to one another
      • Check with a good light source
    • Ensure the chipbreaker is very close to the edge
      • Taking the main blades mimi back and checking visually is really helpful
    • Chipbreaker shouldn’t be loose but doesn’t need to be overly tight either
    • Chipbreaker should have a slight double bevel at steep angle (doesn’t need to be much)
  • Single blade planes can work but require a really tight mouth
    • More difficult to maintain overtime; mouth with open over time and require maintenance
  • Light passes tend to get cleaner results/Harder to stop tearout when taking heavy passes
• Resharpening – how often?
  • Depends on the person, wood, and blade
  • Some woods are more tolerant of a dull blade than others (ex. hinoki, cherry, walnut)
    • You can keep planing for a long time, but resharpening will take longer since you wear out the edge much more
  • Frequent resharpening, before the blade is heavily worn, makes sharpening faster
  • For the best finish plane entire surface, then resharpen for a final series of light passes
• Soft vs Hard wood
  • Can use any steel on pretty much any wood, but some woods require special consideration
  • Soft woods like red cedar or sugi require a really sharp edge
    • Blade doesn’t last long, frequent sharpening necessary
  • Hard wood like oak, keyaki, etc.
    • Blue steel tends to last longer than white, but really depends on the blade
  • Blade width makes a big difference
    • For hardwoods, especially wide panels, a narrower blade will be much easier to pull
• Reducing/Eliminating blade marks/steps
  • 2 methods – cambering blade or rounding corners
  • Rounding corners
    • Easy to maintain when resharpening – maintains a flat edge which makes resharpening more straightforward
    • Greatly reduces the look and feel of steps, but sometimes “soft” lines are still visible in raking light
  • Cambering
    • Slightly more work to maintain between sharpenings
    • Produces a really clean finish
    • Doesn’t work on some really soft woods like red cedar or sugi
      • Edges that transition to zero leave a fuzzy finish
• Reducing/eliminating burnish marks
  • Rabbet or taper sides of kanna so contact points on the dai are the same width as blade edge
    • Requires a lot of control to maintain even pressure and not dig deeper on one side or the other
• Planing wide panels
  • Glue up panels taking grain direction into account
    • Keeps planing direction consistent as well as finished sheen of the planed wood
  • Narrow kanna easier to pull on wide panels
  • Warping/bowing of panel can make planing really tricky
    • A narrow planing beam can help reduce contact area between the workpiece and planing beam, making it easier to plane tricky pieces
      • Need to get creative to support overhanging material and large workpieces
• Dai fit changing over the seasons
  • Blade tends to get looser in summer, tighter in winter
    • Watch the sides of the blade/dai fit especially during winter
  • Cutting dai in spring or fall can result in a nice balance
  • Summer and winter planes?
• Dai changing over the course of a day
  • Humidity changes can have a big effect on dai flatness
    • Require frequent checking and adjustments
  • Put kanna away when not using
  • Oil soaked/finish dai reduce movement, but not a perfect solution
  • The wider the plane and the finer the dai setup the more exaggerated the changes will be
• Fixing loose blade/dai fit
  • Epoxy works great
  • Paper shims work in a pinch
  • Worst case, cut a new dai
• Flat grain vs straight grain planing
  • Flat grain tends to require more physical effort to pull the plane
    • Ring porous woods especially tricky
  • Straight grain tends to be easy to pull
    • Tearout still a possibility
      • Especially with quartersawn oak and woods like sapele
• Good light is crucial to see tearout and the quality of finish
  • Some tearout is deceptive
  • Broad/even fluorescent light is not revealing, can be hard to see tearout and grain detail
  • Natural raking light is great