Hand Tools Archive

Some accurate documented cap iron history

Bill Tindall, E.Tn.
Below there was some inaccurate cap iron history posted by Warren. To correct this history:

Some time in late 2011 I was following the seminal work of Steve Elliot on sharpening, when he provided me with some still images for what we came to known as the K&K video. Apparently I was aware of the cap iron at this time and was sufficiently motivated to learn about how to use it that I set about to track down the source of these still shots of the cap iron working. It was not easy (they were in the midst of the huge tidal wave disaster) but I was able to make contact with the source. From my correspondence with Professor Kato he must have posted it on his University web site in January of 2012 so we could fetch the video from there. I believe from my correspondence Mark Hennebury fetched it for us. Audio was translated by someone in our woodworking club and the video and the translation sent to Horne, Elliot, Pan, Weaver, Hennebury, Ellis and maybe others in April 2012.

copy of email:

-----Original Message-----
From: Bill Tindall [mailto:BJTindall@mindspring.com]
Sent: Wednesday, April 25, 2012 10:35 AM
To: Horne, Wiley; elliott, steve; Weaver, David; Smith, Phil, eastman; Mica
Iwasakim Japanese lady
Subject: History of the Kato Video

Professors Kato and Kawai studied
planing in the mid 1980's. They
comprehensively studied the effect of
the cap iron(chip breaker), blade alloy,
grain angle, etc. under conditions
relevant to hand planing. (I believe
their research was directed toward
SuperSurfacer machines). Their results
were published in Japanese technical
journals is dense technical jargon that is difficult to translate. Some of
the journals have been impossible to find in the US. I have a translation
by Mica and summary written by me to clarify(I
hope) the technical jargon and concepts of the chip breaker study that is
most revealing.

In the quest to track down the journals I could not find in the US I found
and contacted Professor Kawai who has sent me the articles I was unable to
find in US libraries. I now have copies of everything these professors have

These professors were at a technical
college and teaching students was an
important part of their positions. Part of the teaching program was
learning to use hand planes. The parts of Professor Kato and Kawai's work
that was relevant to hand planing was published in educational journals as
an aid to teaching students hand planing. (These were the articles that I
could not find in the US libraries.) To supplement the most important of
these articles(it is not translated yet) they made a video showing the
action of the chip breaker at various distances and angles from the blade
edge upon planing wood with and against the grain. The video reveals in
great detail the mechanics of shaving formation.

Professor Kawai posted this video on his University web site for me. It is
MP3 file and can be easily copied to CD for study.

To help understand the pictures it will be helpful to read the summary I
have made from the translation. I will have it ready to share soon. but
till then the variables studied are distance of chip breaker from tip, angle
on leading edge of chip breaker, and grain angle.
The response is the shaving formation, shaving structure and fracture
ahead of the blade tip.

*** end email

Professor Kato later provided me later with copies of his papers and the video in a package postmarked 05/15/2012. Many of these papers were copied and provided to anyone interested. I had translations made of the key ones and these made available.

I wondered about the apparent absence of interest in this work on WoodCentral. I wrote to Wiley and he responded April 27, 2012
***start of emails
Hi Bill and Steve,

Well, a lot of us are having to change our mind on what the chipbreaker does! Based on Steve's work on this topic, I came to believe that the cap iron could indeed bend the chip so as to prevent tearout--but I saw it as an impractical exercise, since I didn't want to get involved in optimizing the cap iron location at such small distances to the blade edge. For practical purposes, I have been seeing the cap iron only as a means of pretensioning the blade and making it more rigid.

Personally, I have opted for 47.5-55 degree bedding angles and tight mouths, using primarily C&W and infill planes. I love the knowledge and the breakthrough findings!! And I might adjust my LN and Japanese planes, as the spirit moves. But am I going to change my tool choices and planing technique?--probably only at the margins. I do want to make experiments with my Japanese planes--that's where I will apply this new knowledge.

More generally, these findings have tremendous power for two classes of users: (1) Japanese plane users, since the Japanese planes readily available are typically bedded at about 42 degrees and have relatively open mouths; and (2) Bailey or Bedrock type plane users, since these planes have adjustable mouths--you can use your 45 degree standard frog, open up the mouth, and use a close-fit cap iron. [Note that Bevel-Up aficionados are not affected by these findings.]

I don't think silence is quite so strange:

1. Those already committed to C&W planes or infills (high angle, tight mouth) have already made their choice, and may have a slight defensive circle-the-wagons attitude. It's human to do so.

2. Those already committed to Veritas BU planes will not see the relevance for themselves, even though the knowledge is intrinsically stunning.

3. Those using Bailey or Bedrock planes are right now mulling over whether they want to open up their planes' mouths, and tighten up the chipbreaker--or keep the mouth tight. Is the cap iron thing more of a hassle than they want to deal with?

I would ask you, Bill, not in a challenging way but just as a matter of curiosity--have you gotten out your LN 4-1/2, opened up the mouth and tightened the cap iron? What happened? I really think the best way forward from here is to demonstrate the power of this new knowledge by adjusting our Bailey, Bedrock, and Japanese planes and showing the difference in tearout control, while commenting anecdotally on any surface differences we can make out. Honestly, it's very tempting to just go with what is already working, rather than change equipment or relearn planing technique. Though the findings are a revelation in and of themselves.


P. S.--Here are a final few notes on the edit I started the other day. Couldn't do much of value without the figures in front of me:


On Apr 27, 2012, at 10:32 AM, Bill Tindall wrote:

> WoodCentral's most vocal have fallen silent on this plane discussion. Strange.

*** end of email

Some time in the midst of all this Kees posted a video of setting up the cap iron and planing success. Things took off after the Kees video and the followup Article by Kees and Pan. As far as I am able to document Warren had no contribution to advancing use of the cap iron late 2011 till mid 2012 when its use gained wide exposure.

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