Monday, January 14, 2013

Thin on the Ground

I've set a goal for myself this year to improve my planing, and I have come to believe that a hand plane's quality of set up is largely reflected by the quality of shavings it produces. Obviously, one aims for a tear-out free surface, and a flat surface, without tool marks. Beyond that, the wider and thinner the shaving the better, in terms of achieving a optimal result. The shaving should come out of the plane without curling upward. Like a musical instrument, as you approach that point of 'perfection', the greater the number of very minor aspects of set up which come to affect the outcome, and the more demanding and subtle the tuning becomes. It's the same puzzle with a woodworking router for that matter, or grinding lenses for telescopes.

Developing skill at plane tuning takes time, and I am sure I have a lot to learn yet.  Consistent results remotely approaching this continue to elude me:

I am by and large happy with surface quality when I plane a piece of wood. I can obtain a flat surface and leave no tool marks behind, at least on a good day. Trying to go further than that requires some way to gauge progress, and that means going beyond assessing the surface quality to assessing the shaving itself. Namely, full width, fairly flat, and, by the way, how thick is it? It is difficult to measure very thin shavings with any sort of conventional tool, however Mitutoyo makes a type of digital thickness gauge which is well suited to the task:

This is the tool of choice for those in the Kezurō-kai, a group of Japanese craftspeople who meet several times a year to demonstrate traditional woodworking practice and have a competition to see who can produce the widest, thinnest shaving. there is also a Kezurō-kai newsletter, in which tool metallurgy and nuances of sharpening are discussed in great detail. Mike Laine, A craftsman out in California who runs the company Wooden Heart sent me a stack of Kezurō-kai newsletter back issues, which I have been making my way through slowly. That has partly fired me up to work to improve my planing. I think the key to becoming a craftsman is not to settle for anything, to always strive to learn more and develop better technique. Assume that 'you don't know it all' is a good point to start it would seem. I don't know it all, and have found that assuming otherwise usually leads to unfortunate outcomes.

The Mitutoyo gauge measures to a refinement of 0.001mm, or 1 micron:

The current record in Japan for thinnest plane shaving, which I take to be a world record, is 0.003mm, or 3 microns - unless, of course, someone has bested that figure in recent months.

For those who experience blank-outs when seeing metric, 3 microns translates to:


I don't really care to go all-out and strive to match that, as I think it would require an indulgence in kanna-otaku-ness (geeky obsession) to a degree I'm not especially interested in, however I am interested to see where I am at generally at the moment, and then see if I can make some improvements from there. I would definitely like to get into the sub 10 micron zone though. I'm not sure at all at this point how much work lies ahead of me to reach that objective however.

To give a comparison to a commonly encountered item which is considered fairly thin,  I measured a piece of single ply toilet paper. It was 80 microns thick on average.

The measuring gauge is not an inexpensive tool to buy new, however if you are interested in finding one, they do pop up on the used market from time to time. It is model number 547-401:

If I'm not overly appalled at how bad my results are, I may be posting up from time to time over the year to show my progress toward this goal of improved shavings. I guess that wherever I start from in terms of thickness of shaving, I will try to halve that number by the end of the year. Well see - nothing ventured nothing gained.

Thanks for visiting the Carpentry Way.


  1. Is the objective the quality of the finished surface or the of the shavings? If the objective is the quality of the finished surface and time is a constraint then a more meaningful objective might be how thick and wide a shaving can be produced without tear-out or toolmarks.

    1. David,

      Thanks for your comment and question. As I alluded to, but did not state perhaps as well as I could have, this exercise is going beyond the consideration of the finished surface. That is to say, I think one can achieve a perfectly clean, glassy smooth surface (depending upon the species of wood of course) taking, to throw a number out there, 0.05mm thick shavings. From there on into 'thinner land', the reduction in shaving thickness (working on the same material) will probably not improve the surface quality appreciably as far as tool marks or tear out is concerned.

      So, in answer to your question, the objective is not the quality of the finished surface - it will, however, be at least as good as that accomplished when taking a thicker, tear-out-free shaving.

      That does not make the quest to obtain a thinner shaving a waste of time however, any more than striving to run the 100m in under 9.65 seconds is a waste of effort for those involved in that pursuit. Surely a 10 second 100m time is more than adequate, most would think? Heck, the best I ran in High School was 12 seconds - isn't that good enough?

      When Usain Bolt ran 9.58, it shattered quite a few people's ideas as to what was possible for a human being.

      The funny thing when pushing to the limit is that one can learn a lot which can be of great help when not trying to achieve such a tough standard. As I mentioned with an analogy I made in a post back in 2009...


      ...if you can hit the bullseye in a game of darts at will, you can also hit any other number you may care to toss the dart at. The ability to make the hand plane work effectively at ever thinner shaving thicknesses is going to transfer back to having an easier time dealing with problematic situations in planing. Let's face it, if the thinnest shaving you could produce, with your best sharpness and set up with a plane was, say, 0.05mm, and you had tear out, the recourse is what exactly? Choose to scrape or sand? Go to a steeper angled plane? Use a toothing blade and then scrape? In some materials that will be fine, but in others the scraping, sanding or steeper plane blade options will leave an inferior surface.

      We all know that one of the ways of dealing with difficult grain is to make the shaving as thin as possible. If a 0.05mm shaving produces tear out, and one can tune the plane a bit further to shave at 0.008mm, say, then that may well remove the tear out. if it doesn't, and you can't go any finer, then you have run into your personal limit of understanding with that tool in that material.

      So, finding the ways to obtain the thinner shaving, pushing upon against one's current limitations, is very likely to lead to improvements in sharpening, sub-blade setup and tuning, dai conditioning, blade fitting, etc., and every one of those improvements will mean that when taking shavings of a more regular nature, as one would take when doing normal work on a piece of wood, are going to be a bit further within one's capabilities, instead of being more at the edge of one's capabilities.

      Also, I am a person with a lot of curiosity. I see some people in Japan making their 'simple' wooden planes perform like that, and know that I cannot obtain the same result, despite having equivalent quality tools. So, I am interested to find out where the parts of my 'game' are that need work in order to improve. If I'd never seen pictures of people obtaining such thin shavings it wouldn't have occurred to me that it was even possible. So, first order of business really is to adjust the paradigm so as to take in the reality of what actually is achievable.


  2. I see David's (and perhaps others')point of surface quality first regardless of the quality of shavings, but I am a huge fan of trying to get the perfect shaving. The competitions you mentioned are like watching a sport that I can also participate in. It's kind of like watching bike racing as apposed to football. How many people can play baseball or football on a regular basis yet anyone can ride a bike and appreciate the talent involved in a bike race. Probably everyone who reads this blog uses (or has tried to use) a plane with varying results. Being able to take full width superthin shaving is extremly exciting for me (maybe I need to get out more). Everytime I have planed a board to a flat smooth finish the resulting shavings have been like fine silk ribbons, and while no one else ever sees them it gives me an additional reason to be happy the final product.


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