Using a Sumisashi and Sumitsubo
by Mathieu
Upon request of several readers we will have a closer look at how you can use some of the Japanese layout tools I discussed in the previous post.
Snapping Lines with a Sumitsubo
Make sure your sumitsubo is prepared well and ready to go. See this post.
Since we snap center lines we have to mark the center first.
Mark the center by measuring and placing a tick mark.
Note how I use 100mm at the edge to increase accuracy. The lens of this camera creates a false perspective. It appears that the stick is less then 60mm but in fact it is exactly 60.
Trick:
Set a marking/scribing gauge to distance approximately half the width of the piece. (about 1mm larger) Mark from either side and you will find the center exactly in between both marks. Very fast, convenient and accurate.
Pin the line either to the end grain or on the surface. I prefer the end grain and early wood since it doesn’t leave a hole on the surface and the pin is easier to remove. When removing the pin after snapping twist it while pulling to avoid bending the metal pin.
You can rotate the pin to get your line spot on your mark. And make sure you tie the line to the metal pin with a halfknot.
After unrolling you can either grab the line before you place the other end on the mark or place the line down while creating tension on the line, the reel is now locked with your thumb or by the palm of your hand.
In order to make sure you snap a straight line without any curvature you have to hold your head still. Put down the line on the mark, make sure you have the right amount of tension and tap the line in front of you. This creates a tick mark. Now without moving your head you lift the line straight up and snap it aiming for the tick you just made.
The centerline is then marked with a Z-type mark.
Voila, two hundred and fifty eight words later we have… a line.
Good or Bad
When holding the sashigane to make marks hold it with one hand and bend it slightly to lay it flat on the surface. The friction between the thickened corner and the blade should be enough to keep it in place.
This might take some practice but avoid using your fingers to hold the blade while marking a line. Sometimes you have to but in general this is considered bad practice.
Laying Out a Mortice
If you align the bottom side of the long blade with your centerline (CL) and mark along the top you have drawn a line that should be exactly 15mm (the width of the square) away and parallel to the CL. Often a mortice is located directly upon the CL. Let’s say your tenon is 90mm wide (which is common) you have placed the long blade with the bottom along the CL and the crossing CL at the 45mm mark. This way you can draw two sides of the mortice at once.
Without moving the square you have placed a tick mark at 90mm.
Use this tick to mark the other short side of the mortice holding the square to the edge of the timber.
Only one side of the mortice remains to be marked and often I flip the square to draw this line since then the short blade has a longer bearing surface on the timber which aids a bit in accuracy.
Mark the mortice and mark the depth if necessary. Eventually you add about 2mm of clearance to avoid that the tenon will bottom out. I Wouldn’t write 122mm, it is something you just know while cutting out the mortice.
All the above takes about 7 to 8 seconds.
Secret Tricks
For what I am about to tell you the guardians of secretive craftsmanship might come and hunt me down. I couldn’t care less and in these times of global industrialism I will do anything that contributes to the continuation of this ancient craft. The last thing we need today is secrecy.
Take a fine file and make a mark on your sashigane at 28mm. You can now quickly use this to mark the offset of the pegholes of your tenons. Seconds saved, consistency guaranteed.
Invest in a reel of superfine braided dyneema fishing line and replace your sumitsubo inkline with this stuff. They don’t soak up too much ink thus leave a clearer and fine line. They are super strong and last a long time.
Cut back the top on the tip of your sumisashi, it will make it write in both directions which works great when doing layout on round logs.
And remember, when laying out always think in function of the centerline!
This post has been a new experience for me and is written in a truly internet-like, how-to, step-by-step-guide way. I hope it will be useful to some. It seems a bit superficial but maybe that is just me being old fashioned. The next step up from here is video tutorials. Cold shivers down my spine when I only think of it. I don’t know I could ever go there, I am sorry. Pictures and text will have to suffice.
∴
HI Mathieu,
Thank you! That was brilliant.
Not sure what’s needed more than this. I think you did great, and the text and pictures are more than clear.
IF you would do a follow-up, then perhaps an outline of how you prepare/square big timber using only hand tools would be of great interest.
Perhaps you could just photo-document the next time you are working with a big piece of house-timber?
ALSO your method of fitting irregular or round timbers would be very interesting.
This is so clear and concise. Very cool. Thanks.
– Henrik
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This is wonderful, thank you! Finding English speaking professional woodworkers who use Japanese tools and techniques has been a rare thing on the internet, I’m very excited if this is a new trend. Really appreciate the thought and time you put into these posts.
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But, and in a partial answer to my own question, perhaps you don’t think that much in terms of flat and square for layout?
Do you just use the center line as the constant reference – and is there then no need for a fair face and square edge?
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Hi Henrik,
I will see what I can do. But it will be ont thing at a time.
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If it is a trend then it certainly isn’t one of the temporary fashion type..
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The centerline is always the main reference and everything is measured from there outwards. If you have a flat face and square edge all the better and you can use them to be more efficient but it is not mandatory. Especially when using round or irregular timbers centerline layout is very effective.
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Hi Mathieu,
See, now I get it:-)
Thanks!
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I would also like to add my appreciation for your tutorial. I am one of those who have great difficulty not holding the sashigane with my fingers. More practice I guess. Maybe the fact that I am using a mechanical pencil for marking is putting to much side pressure.
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Thanks so much for this! Lots of tips I’d never seen before.. Also now you’ve introduced another mortise mark, the arc between corners. If dots are through mortises and slashes are blind mortises, arcs are… ?
Not quite sure about the purpose behind the super-secret tip, though – are you talking about drawbore holes?
My former teacher also used round circles in some of his mortises, but never explained why. Now I am wondering whether these designated through mortises that were pegged. ???
Darrell
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Thank you so much for these basic tips and treasures! I couldn’t agree more of how nice it is to have Japanese tools and techniques explained in our language. Greatly appreciative
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You are most welcome.
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Darrell,
The arches are just another variation on the dots.
Usually the square pegs are located at 30mm from the edge. 28mm gives a good offset to draw them together.
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David,
Just stick to the good practice. it is easier to lear then you might think. A mechanical pencil should work just as well.
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Though I work in another tradition and seldom ping a line through the center, my approach like yours is datum dependent and I do use ink lines and own a sumitsubo.
I do appreciate the ability you afford to to view a parallel journey, as you say, through another perspective.
Thanks for sharing.
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Hi Mathieu
Glad again to read your great blog. I have enjoyed it a lot I think this entry is full of good knowledge. I really appreciate your help sharing all this gorgeus info. I just can say, thanks a lot. See you Sensei.
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Appreciate the comment but ‘sensei’ i am not
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I believe you are a teacher to me. Your kindness is a terrific lesson. If sensei is something bad I promise I won´t call you that again
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It’s not bad at all just not what I am. I’m happy it was helpful to you though.
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Great post Mathieu as always. I feel the little things are the important things.
And the big things are formed by little things.
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Andy,
Happy to hear that you got something out of it.
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Love your blog, it is very infomative
What do you consider a superfine fishingline ?(in mm)
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Hi Juryaan,
Nice to hear that you like the blog.
At the moment I am using a 0.2mm line which works really well.
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Hi Mathieu , what happened? Really looking forward to the continuation of the theme.
Istvan
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Mathieu, do consider video. Your manners are modest and kind, your love of fine points infectious, and the sight of hands in action is a great help for people to, hmm, grasp and emulate. And your friends would love seeing it.
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Hi William, thank you for the encouragements.
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Written with great clarity and insight
Much appreciated that hard earned knowledge is shared for free.
Book
The Complete Japaneese Joinery
Emphasises the centre line as everything
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