Matsui Seimitsu Precision Squares

Maestro Bruno Walter 1876~1962

By concentrating on precision, one arrives at technique, but by concentrating on technique one does not arrive at precision.

Bruno Walter

We would like to introduce some excellent tools made by a company called Matsui Seimitsu Kogyo located in the city of Sanjo in Niigata Prefecture in Japan. We have been using this company’s products for many years and have started carrying a few by popular demand. The time has come to share these with our Beloved Customers in general.

Matsui Seimitsu Kogyo translates to “Matsui Precision Industries,” but I’m just going to call them Matsui Precision. The company has been around for over 100 years. They may not be the largest manufacturer of precision tools in Japan, but their reputation is unsurpassed.

Allow me to digress for a moment while I grind these oak galls to make some ink. Just about out, you see. Anyway, as you can probably tell from my posts to this blog so far, and which will become even more obvious in the future, I love ancient tools and learning how beautiful work was done by determined people using basic, even crude tools. But I am also fond of excellent refined handtools that help me do a better job more efficiently. I am always on the lookout for such tools, and this post is about one such tool I discovered. One thing I like about this tool is that while it is essentially unchanged from the days when Noah was knee-high to a grasshopper, Matsui Precision has subtly improved the ancient and lowly square in ways that are not immediately obvious. For one thing, it really is a “Precision Tool,” even though you wouldn’t think so just by looking at it.

The idea of using “precision tools” for woodworking is offensive to some. I have seen online discussions of precision tools induce psychotic events in some amateur woodworkers. Perhaps the thought of such tools triggers hallucinations of digital micrometers swooping through their dreams while pissing down on the eternal beauty flowing from their masterful hands. Or perhaps they imagine the smelly poor-quality Chinese-made tools they buy in bundles from Harbor Freight to be more expressive than the cold precision tools of the sort less artistic machinists use. To the former I say “Don’t drink alcohol with your medications.” To the latter I exhort: “Extract your head from your nether regions and behold the light of civilization!” 

Anyway, that’s enough ink to last a month, so enough free psychoanalysis. Let’s get back to Matsui Precision Squares.

They have six distinct advantages over almost any other simple square you will find:

  1. Precision: Unlike any square ordinarily available to woodworkers, these are manufactured and certified in accordance with Japan Industrial Standards (JIS). The relevant standard is JIS B7516 (2005). The hardened steel model (SY Series) is rated Grade 1, and the graduated model SM Series) is rated Grade 2. Accordingly, these squares precisely measure 90°. Without using other precision instruments the only way to confirm this claim is with another high-precision machinist’s or diemaker’s square. The MP square will pass this test, not to woodworking tolerance, but to machinist’s tolerances. We guarantee it.
  2. Lightweight and Handy: You will not find a precision square lighter or handier. The blade (long leg) and stock (short leg) are relatively thin, light in weight, and handy to use, unlike machinist’s squares and combination squares with their thick, heavy, clumsy, flat stocks and blades which make it difficult to see light showing between them and the workpiece. The Matsui blade is relatively thin making the square easy to use for woodworking.
  3. Durable: The stock and blade of both SY and SM series tools are joined by spot welds, unlike all but the most expensive machinists squares; Not a compression joint, not glued, not bolted, not pinned. They are not indestructible, of course, but the stock or blade will bend or melt before this connection fails.
  4. Corrosion-Resistant: both blade and stock are stainless steel so they won’t rust even if used and stored in constantly humid conditions, even if you have sweaty hands.
  5. Hardened: This feature is most important in my opinion. The blade and stock of the SY series squares are hardened, a very unusual feature. For the woodworker, this means that the blade will better endure the scraping and shaving action of steel scribes and heat-treated marking knives used in layout and stay straighter much longer than all but the most expensive machinist’s and diemaker’s squares.
  6. Relief Cut: The stock has a small half-circle notch cut into where it meets the blade to prevent wood shavings etc. from jamming between the blade and/or stock preventing them from making clean contact with the workpiece ruining accuracy, an important detail indeed.

In short, the Matsui Precision square will help you do better woodworking, easier, and for many years.

We carry two models of Matsui Precision squares. The first is the SY Series pictured below, with a hardened stainless steel blade but without graduations. The stock is hardened to Rc54~57 and the blade to Rc48~52. This is the tool we use and recommend for layout using a marking knife.

The SM series is different from the SY Series in three ways, reflected in the lower price. First, the blade is not hardened. Second, it has deeply etched graduations (not laser etching) which are perfect for using with a scribe or marking knife because the tool’s tip can get into the graduation for positive indexing. And third, the level of precision is one level lower at JIS Grade 2. The graduations include a √2 scale useful for determining the diagonal distance of a square by measuring a side.

If you are tired of squares that aren’t square, that are bulky, heavy, and clumsy to use, that are destroyed by a single drop, or that get eaten alive by your marking knife or scribe, then you should give these a try. You’ll never look back.

If you would like to purchase one, please inquire using the form below.

Matsui Precision Hardened Stainless Steel Squares (w/o graduations) Model SY-15
Product IDNominal Size (mm)Blade lStock lStock t¥ Price
SY-550524086,270
SY-770725686,270
SY-101001057086,270
SY-151502029986,820
SY-2020025212288,690
SY-252502521481012,320
SY-303003021761015,180
Matsui Precision Hardened Stainless Steel Squares (w/o graduations)
Matsui Precision Stainless Steel Square (w/o graduations) Model SM-10
Product IDNominal Size (mm)Blade lStock lStock t¥ Price
SM-550524083,080
SM-770725683,080
SM-101001127083,080
SM-121201408583,080
SM1515017010083,300
SM-2020022512084,840
SM-2525027514510.56,820
SM-3030032517310.58,800
Matsui Precision Stainless Steel Squares (w/ graduations)

If you have questions or would like to learn more about our tools, please use the questions form located immediately below. Please share your insights and comments with everyone in the form located further below labeled “Leave a Reply.” We aren’t evil Google or incompetent facebook and so won’t sell, share, or conveniently and profitably “misplace” your information.

5 thoughts on “Matsui Seimitsu Precision Squares

  1. About 18 years ago I bought a Starrett 300mm combination square with a hardened steel ruler and head. It’s still dead square. It was expensive even back then but that’s the price you pay for this kind of quality. I also have a larger, flat square (600x400mm) that a machinist friend made for me out of a single piece of 4mm thick steel. Also dead square and perfect for laying out an interior in a boat. The way he made it ensures it will never go out of square. Some people will say this is over the top for a boat interior but it really isn’t. A single corner that isn’t perfectly square isn’t noticeable, but when you add it all up a boat interior just looks cleaner and tighter when everything that needs to be square is indeed perfectly square. Your eyes can tell the difference. Drawing of the flat steel square: https://i.imgur.com/shvF9Ku.jpg

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    1. Henk:

      Thanks for the insight. Always most welcome.

      I agree that precision and quality in layout tools is critical. Some things are relative, like the width of a mortise or thickness of a table leg, while other things like square and straight must be nuts-on. Anyone who has met Murphy knows that errors do not cancel out but accumulate, to be revealed only a few minutes before any deadline.

      I too have the same Starrett combo square in my toolchest. I wore out a Mitsutoyo before that. The downside to the combo square is they don’t handle being dropped well. And Starrett quality is not what it once was, sadly.

      I like the square. What is the material? Any special treatments?

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  2. The steel is nothing special, the same stuff that’s used to make a boat hull. Just a simple low carbon, high tensile steel. He machined it on his CNC machine so the outside corner is dead square. He also made an accessory for it so I can use it standing up. It’s just a flat piece with two uprights that each have two magnets on the inside so the square stays in place. Simple but effective. I polished the square on a buffing wheel to give it some corrosions resistance.

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  3. I have never regretted any of my precision tools. Sometimes ‘unnecessary’ for woodworking but when has that rule ever applied in earnest 🙂 I feel it is better to know than to guess in the pursuit of ever smaller gaps.

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