Eighth post in a series describing the set up of a new Japanese hand plane, kanna.
------------
In the previous installment we looked at aspects of fitting the sub blade (osae-gane), to the main blade (kanna-mi) block (dai) and fixing pin (osae-bō). There we saw that the tightness of fit between the sub-blade and fixing pin could be adjusted by the manner in which the fit between the sub-blade and main blade is tuned. Still, despite one's best efforts, one can be left with a situation where the fit of the sub-blade remains a bit loose under the osae-bō and today's post deals with how that may be resolved.
A 'loose fit' is hereby defined as a situation where, with the kanna-mi fully seated in the dai, the sub-blade can be pushed into position without too much effort using moderate finger pressure:
![]()
Or anything looser than this - - I've seen new planes where the sub-blade can slip almost out of the mouth without the fixing pin doing much of anything. These cases are often the result of an uncaring/ignorant tool seller simply throwing parts together which were never initially fitted to one another in the first place.
A temptation might be to simply hammer down on the middle of the fixing pin to bend it downward. This would increase pressure on the chipper, but the solution would be short-lived. Making the fixing pin into a bowed shape now gives the sub-blade leverage to rotate the pin, and, as soon as the pin rotates, the tightened fit is immediately lost. Bad idea. You could perhaps get away with it if the fixing pin was square or polygonal in section, as a few are, but the leverage problem remains and the pin will ultimately start to work to spin in its mounting holes. So, such a 'solution' is best set aside as ill-advised.
Osae-bō are usually cylindrical pins, and there are two standard nominal sizes, 4.0mm (0.15748") and 5.0mm (0.19685"). If your plane has a 4.0mm pin and the osae-gane is a really loose fit under the pin, then you could possibly look at jumping right up to the larger size. In the case above, the osae-gane is loose, but not overly so, and jumping from 4.0mm to 5.0mm would result in an overly-tight fit. At least that was my estimation.
So, what is needed here is a fixing pin of an intermediate dimension, somewhere between 4.0 and 5.0mm. Fortunately, though there are no 'official' ones, made by someone with a hachi-maki under a full moon with full approval of the Japanese Ministry of Culture, there are metal rods available which make admirable substitutes. Gasp - more non-traditional things here. I hope nobody is starting to feel uncertain or getting a sense of dread. Hang in there if so.
I speak of what is termed 'tight tolerance' rod, which comes annealed and is meant for the fabrication of drill bits. In the US, one source of such precision ground tight tolerance rods, made of O1 tool steel, is McMaster-Carr. The rods are only available in 36" lengths, however they are relatively inexpensive at $3~$5/piece.
Before ordering rod if might be worth trying to get an idea of what sort of dimensional change to the fixing pin would result in a decent fit, and this can be done by using those good old feeler gauges:
![]()
Check for the fit with the main blade fully seated in the dai. The feeler gauge is indicating the increase in pin radius required. It's not an entirely precise method, as the fixing pin can itself bend with the feller gauge underneath, however it gives a rough idea.
The pin is removed from the dai fairly easily, when there are no cosmetic plugs fitted to the pin holes, by simply using a drift pin to tap the sucker out:
![]()
With the pin out, its actual size can be measured:
![]()
3.97mm is 0.15630". I'm going to use metric numbers as well as inch-scale, as many readers of this blog are from outside the US.
I also took a measure of the 5.0mm (nominal) pin:
![]()
From testing the fit with feeler gauges, I had the ballpark idea that a pin which was 0.005" greater in radius - i.e., 0.010" fatter in diameter - would be about right as a starting point. Adding 0.010" to 4.0mm (0.15630") gives 0.16630" (4.22mm). Looking at the sizes of tight tolerance rod available, I selected one length of 0.1680" and one length of 0.1750". I also came across a 3" piece of rod measuring 11/64", or 0.171875". So that gave me a range of possibilities jogging up from 4.0mm to 5.0mm, roughly in 0.2mm increments.
I started with the first size in my pile, the 0.1680" rod, which is 4.2672mm:
![]()
This is where having a larger drill index on hand is really useful. Standard fractional drills are too limiting, you need to be able to select from the numbered drills:
![]()
With a 0.1680" pin to be fitted, I selected the #19 drill, which measures 0.166", or about 4.2164mm, at least it is supposed to:
![]()
Seems a hair under, but it was worth a go. I clamped the dai to a block of wood with a checked 90˚ arris, and drilled out the hole to this size:
![]()
Hole done, I cut the 0.1680" rod to length, with the old osae-bō as a length gauge:
![]()
I chamfered the cut rod and fitted it to the dai. Then it was time to check the fit of the osae-gane:
![]()
It was improved, a bit tighter, but still a bit too loose for my liking. Out comes that pin.
The next size up in my collection of rod was 11/64", however I decided it would be better to jump to the 0.1750" rod, which is 4.445mm:
![]()
My initial estimation that a 0.01" fatter fixing pin would be about right proved to be an underestimate.
The same steps are followed and the larger pin was then fitted. This time the fit was just right, and the last part of the sub-blade seating required some light taps with the mallet handle end:
![]()
You can see, I hope, that with this method any issues with an undersize osae-bō can be dealt with relatively easily.
------
A reader wrote to me and asked if it was a good idea to trim the edge corners of the osae-gane in the same manner as the main blade. I've done this in the past, but it is not the best idea.
With the main blade's mimi trimmed, the osae-gane corners will protrude at each side:
![]()
The handy thing about this fact is that one can use it to judge how close the sub-blade edge is to the main blade edge:
![]()
It can be tricky sometimes to sight the set back of the sub-blade from the main blade by looking down into the mouth of the plane, especially with a tight mouth opening or marginal light conditions, so having the option of the flipping the plane upside down and checking be looking at the osae-gane corner is helpful.
A final step once the main and sub-blade have been fitted is to chamfer the lower edges of the dai:
![]()
The upper arris of the dai-gashira, the spot where you hammer to raise the blade up in the plane, should also be judiciously blunted with a chisel and plane so as not to be prone to any chipping or denting.
That about does it for this overview of the plane set up process. I hope the reader has found it informative. I feel I have brought to light some information not previously available in English. There's a lot to these 'simple' tools.
Here's hoping your shavings are thin and wide, your surfaces glassy and smooth:
![]()
All for now. Thanks for visiting the Carpentry Way.
------------
In the previous installment we looked at aspects of fitting the sub blade (osae-gane), to the main blade (kanna-mi) block (dai) and fixing pin (osae-bō). There we saw that the tightness of fit between the sub-blade and fixing pin could be adjusted by the manner in which the fit between the sub-blade and main blade is tuned. Still, despite one's best efforts, one can be left with a situation where the fit of the sub-blade remains a bit loose under the osae-bō and today's post deals with how that may be resolved.
A 'loose fit' is hereby defined as a situation where, with the kanna-mi fully seated in the dai, the sub-blade can be pushed into position without too much effort using moderate finger pressure:
Or anything looser than this - - I've seen new planes where the sub-blade can slip almost out of the mouth without the fixing pin doing much of anything. These cases are often the result of an uncaring/ignorant tool seller simply throwing parts together which were never initially fitted to one another in the first place.
A temptation might be to simply hammer down on the middle of the fixing pin to bend it downward. This would increase pressure on the chipper, but the solution would be short-lived. Making the fixing pin into a bowed shape now gives the sub-blade leverage to rotate the pin, and, as soon as the pin rotates, the tightened fit is immediately lost. Bad idea. You could perhaps get away with it if the fixing pin was square or polygonal in section, as a few are, but the leverage problem remains and the pin will ultimately start to work to spin in its mounting holes. So, such a 'solution' is best set aside as ill-advised.
Osae-bō are usually cylindrical pins, and there are two standard nominal sizes, 4.0mm (0.15748") and 5.0mm (0.19685"). If your plane has a 4.0mm pin and the osae-gane is a really loose fit under the pin, then you could possibly look at jumping right up to the larger size. In the case above, the osae-gane is loose, but not overly so, and jumping from 4.0mm to 5.0mm would result in an overly-tight fit. At least that was my estimation.
So, what is needed here is a fixing pin of an intermediate dimension, somewhere between 4.0 and 5.0mm. Fortunately, though there are no 'official' ones, made by someone with a hachi-maki under a full moon with full approval of the Japanese Ministry of Culture, there are metal rods available which make admirable substitutes. Gasp - more non-traditional things here. I hope nobody is starting to feel uncertain or getting a sense of dread. Hang in there if so.
I speak of what is termed 'tight tolerance' rod, which comes annealed and is meant for the fabrication of drill bits. In the US, one source of such precision ground tight tolerance rods, made of O1 tool steel, is McMaster-Carr. The rods are only available in 36" lengths, however they are relatively inexpensive at $3~$5/piece.
Before ordering rod if might be worth trying to get an idea of what sort of dimensional change to the fixing pin would result in a decent fit, and this can be done by using those good old feeler gauges:
Check for the fit with the main blade fully seated in the dai. The feeler gauge is indicating the increase in pin radius required. It's not an entirely precise method, as the fixing pin can itself bend with the feller gauge underneath, however it gives a rough idea.
The pin is removed from the dai fairly easily, when there are no cosmetic plugs fitted to the pin holes, by simply using a drift pin to tap the sucker out:
With the pin out, its actual size can be measured:
3.97mm is 0.15630". I'm going to use metric numbers as well as inch-scale, as many readers of this blog are from outside the US.
I also took a measure of the 5.0mm (nominal) pin:
From testing the fit with feeler gauges, I had the ballpark idea that a pin which was 0.005" greater in radius - i.e., 0.010" fatter in diameter - would be about right as a starting point. Adding 0.010" to 4.0mm (0.15630") gives 0.16630" (4.22mm). Looking at the sizes of tight tolerance rod available, I selected one length of 0.1680" and one length of 0.1750". I also came across a 3" piece of rod measuring 11/64", or 0.171875". So that gave me a range of possibilities jogging up from 4.0mm to 5.0mm, roughly in 0.2mm increments.
I started with the first size in my pile, the 0.1680" rod, which is 4.2672mm:
This is where having a larger drill index on hand is really useful. Standard fractional drills are too limiting, you need to be able to select from the numbered drills:
With a 0.1680" pin to be fitted, I selected the #19 drill, which measures 0.166", or about 4.2164mm, at least it is supposed to:
Seems a hair under, but it was worth a go. I clamped the dai to a block of wood with a checked 90˚ arris, and drilled out the hole to this size:
Hole done, I cut the 0.1680" rod to length, with the old osae-bō as a length gauge:
I chamfered the cut rod and fitted it to the dai. Then it was time to check the fit of the osae-gane:
It was improved, a bit tighter, but still a bit too loose for my liking. Out comes that pin.
The next size up in my collection of rod was 11/64", however I decided it would be better to jump to the 0.1750" rod, which is 4.445mm:
My initial estimation that a 0.01" fatter fixing pin would be about right proved to be an underestimate.
The same steps are followed and the larger pin was then fitted. This time the fit was just right, and the last part of the sub-blade seating required some light taps with the mallet handle end:
You can see, I hope, that with this method any issues with an undersize osae-bō can be dealt with relatively easily.
------
A reader wrote to me and asked if it was a good idea to trim the edge corners of the osae-gane in the same manner as the main blade. I've done this in the past, but it is not the best idea.
With the main blade's mimi trimmed, the osae-gane corners will protrude at each side:
The handy thing about this fact is that one can use it to judge how close the sub-blade edge is to the main blade edge:
It can be tricky sometimes to sight the set back of the sub-blade from the main blade by looking down into the mouth of the plane, especially with a tight mouth opening or marginal light conditions, so having the option of the flipping the plane upside down and checking be looking at the osae-gane corner is helpful.
A final step once the main and sub-blade have been fitted is to chamfer the lower edges of the dai:
The upper arris of the dai-gashira, the spot where you hammer to raise the blade up in the plane, should also be judiciously blunted with a chisel and plane so as not to be prone to any chipping or denting.
That about does it for this overview of the plane set up process. I hope the reader has found it informative. I feel I have brought to light some information not previously available in English. There's a lot to these 'simple' tools.
Here's hoping your shavings are thin and wide, your surfaces glassy and smooth:
All for now. Thanks for visiting the Carpentry Way.