A machinist square is way more accurate in terms of checking squareness compared to the other types of square tools. This accuracy comes from its stable body, manufacturing accuracy, and material. No part of its body is pinned or riveted. The head and blade are integrated directly with no conjunction.
This machinist square comes with a grade that represents its accuracy or tolerance level. Its inside or outside corner may have different tolerance level. You should take care the spec before purchasing.
The lower-grade machinist square can be used directly as a tool. You could use it to adjust the angle of a table saw so it shapes a 90 degree angle relative to its base. Also, you could use it for checking the squareness of some wood board’s corners you just sawed.
On the other hand, the higher grade can be used for inspection and even calibration of the lower-grade squares such as try square and framing square.
The best machinist square is relative to the users. The lower-grade ones are suitable for small workshops. On the other hand, Professional CNC machine shops should opt for the highest grade. In this article, we are covering several machinist squares on the market that comes from the lowest to the highest grade. Even, we add a master square block. So, if you are seeking one whether for machinist, woodworking, metalworking, and even lab use, hopefully, this compilation helps a lot.
Top 10 Best Machinist Squares in 2024
Many designs and sizes of machinist squares exist. Their accuracy and precision also differ according to the grade level, and that determines the applications they are suitable for. This best machinist square review is a compilation of different products from market research and testing. Every item on this list is professionally approved for the purpose. Read on to pick your best!
| Products | Images | Squareness | Size | Price??? |
|---|---|---|---|---|
| 1. Groz SS/A2 Machinist Square |  | .00063" | 2”, 3”, 4”, or 6” | Price! |
| 2. Accusize Industrial Tools Machinist Square Grade 0 DIN 875 |  | Inside angle: .0002756" Outside angle: .000315" | 6 inches | Price! |
| 3. Moore and Wright Grade B (B.S. 939) |  | Grade B | 12 inches | Price! |
| 4. Starrett 3020-3 Toolmakers Square |  | 0.005mm (.0002") for every 150mm (6"). | 2-31/32” | Price! |
| 5. Starrett 20-6 Master Square |  | .0001" (0.0025mm) every 6" (150mm) | 6 inches | Price! |
| 6. Mitutoyo 311-111 |  | Better than 1µm/300mm | 210.0 inches but there are smaller options | Price! |
| 7. iGaging 34-B06 Grade 00 (DIN 875) 2" and 6" (Affordable Choice) |  | +/-.1" | 6 inches | Price! |
| 8. iGaging 34-246 Grade 1 (DIN 875) Square Set |  | .001" | 2", 4", and 6" | Price! |
| 9. Steelex D3383 Precision Square |  | ±.0006" | 4 inches | Price! |
| 10. Faithfull Engineers Square |  | Not Specified | 4 inches | Price! |
1. Groz SS/A2 Small 2″ Machinist Square
Groz SS/A2 is an excellent piece of a 2″ small machinist square for everyday workshop use. It is the right choice if you are working on smaller workpieces and tight on budget.
This machinist square is designed with hardened steel blades to enhance durability and reliability. Once bought, this instrument retains its shape and accuracy for decades under the right conditions. Both blade and stock are ground and lapped to ensure this machinist square maintains its straightness and parallelism over time.
Groz SS/A2 Machinist Square is handy in setting up and checking carpenters’ squares when marking joints. It is also the tool you need for testing faces and edges for straightness.
Nicely, the 3″, 4″, 6″, and a bundle one (2″, 4″, and 6″) squares are also available.
Buy Now!Spec:
- Grade: B based on BS 939 standard
- Squareness: .00063″ (16 µM)
- Size: 2″
Pros:
- Affordable
- Has both inside and outside true right angles
- High-quality and durable
2. Accusize Industrial Tools 0303-6203 Machinist Square Grade 0 DIN 875
Accusize Industrial Tools Machinist Square boasts high precision of the inside and outside angles. Since it is a grade 0 tool, you can use it for applications that require the best accuracy. Additionally, you can make use of both inside and outside angles.
The Accusize Industrial Tools Machinist Square is designed with a beveled blade. Both beam and blade are lapped for straightness and parallelism and made of fully hardened steel for durability and reliability.
This machinist square is best suited for woodworking and metalworking projects. You can rely on it to verify the squareness of other structures you are making at the workshop or renovation site. It is the best choice for quality control technicians and inspectors.
Spec:
- Grade: 0 based on DIN 875 standard
- Inside squareness: 275.6µin (.0002756″)
- Outside squareness: 315µin (.000315″)
- Blade length: 6”
- Beam length: 4”
Pros:
- Relatively affordable
- Ergonomically designed
- Reliable and accurate
- Strong and durable
- Comes with a wooden case for safe storage
Cons:
- Lacks a brand name on it
3. Moore and Wright 40012 Grade B Engineer’s Square
Moore and Wright is a grade B Engineer’s Square manufactured as a very accurate tool. They come in different sizes, but this particular product is 12 inches long and has a 12″ (300 mm) precision ground blade and 7-1/4 inch (184mm) stock.
This product is engineered to maintain its squareness to eternity. It features blind riveted construction with hardened and tempered blades. You will enjoy reliability and accuracy in different applications, including woodworking and metalworking.
Buy Now!Pros:
- Accurate
- Reliable and durable
- Great value for money
- Suits different applications
Cons:
- Susceptible to rusting
4. Starrett 3020-3 Toolmakers Machinist Square
As the name suggests, Starrett 3020-3 Toolmakers Square is a toolmaker’s grade stainless steel measuring tool. It has a combination of two straight edges set at right angles for measuring both inside and outside squareness. This tool is best for carpenters and machinists who regularly check workpieces.
Starrett 3020-3 Toolmakers Square is made of a hardened stainless-steel blade and a beam that resists corrosion and rusting. The beam is machined at the inner corner to provide clearance. Its premium quality gives it an accuracy of 0.0002″ (0.005 mm) for every 6″ (150 mm).
This product comes with a plastic storage case to help you keep it safe after use. Other sizes also exist. So, you can choose what will work best for your application.
Buy Now!Pros:
- Very accurate
- Rust and corrosion resistant
- Comes with a safe plastic storage case
- Machined beam for clearance
Cons:
- Relatively expensive
5. Starrett 20-6 Master Square
Starrett 20-6 Master Square is a mid-range tool with an accuracy of .0001″ (0.0025mm) every 6″ (150mm). If you can meet the budget, it is a good choice for many applications which require such a high level of precision.
Like other models from Starrett, Starrett 20-6 Master Square has a beam machined inside to provide clearance for burrs and dirt. That feature makes the tool easy to use and fast checking the squareness of the workpiece.
Starrett 20-6 Master Square is made of hardened steel. Both the beam and blade are also hardened, ground, and lapped for straightness and parallelism.
Buy Now!Pros:
- Finest precision-checking squares
- Hardened steel blade for durability and reliability
- Grooved inner side of the beam provides clearance for burrs and dirt
- High quality
Cons:
- Expensive
6. Mitutoyo 311-111 Master Square Block
Mitutoyo 311-111 is a high-end, high-precision square ideal for inspecting other measuring instruments for squareness and straightness. Unlike conventional L-shaped machinist squares, Mitutoyo 311-111 has an overall square design with circular grooves drilled through it.
The ideal application of Mitutoyo 311-111 is checking the accuracy of high-precision instruments and XY tables. It is the best tool for inspecting the straightness of each axis, but only if you can afford it.
Buy Now!Pros:
- Very high accuracy
- Three different sizes are available
- Four precision lapped reference surfaces
- Comes with a fitted wooden box for safe storage
Cons:
- Very expensive
- Available in metric only
7. iGaging 34-B06 Grade 00 (DIN 875) 2″ and 6″ (Affordable Choice)
iGaging 6 is a beveled edge square with right angles inside and outside. Its blades are made of special hardened carbon steel for strength and durability. It is not all that accurate, but it is still ideal for some applications. iGaging 6 has an accuracy of 0.1 degrees.
Buy Now!Pros:
- Affordable
- Long-lasting
- Easy to use
Cons:
- Not very accurate
8. iGaging 34-246 Grade 1 (DIN 875) Square Set
iGaging Machinist Square comes as a set of three tools of different sizes. But you can buy them individually if you don’t need all three. Their sizes are 2, 4, and 6 inches, respectively.
iGaging Machinist Square has all surfaces ground for straightness and parallelism, making them accurate on the inside and outside. They are not graduated but are still easy to use on different applications. You can use them to set your table saw blades, jointer fences, and many other machine tools.
Buy Now!Pros:
- A set of three machinist squares of different sizes.
- Ground on both sides for straightness and parallelism
- Affordable
- Comes with a safe storage case
Cons:
- Not very accurate
9. Steelex D3383 Precision Square
Steelex D3383 Precision Square is the most affordable option on this list, the ideal choice if working on a tight budget. This machinist square is cost-effective but still has many features of some expensive models. Firstly, it is accurate. Secondly, Steelex D3383 Precision Square has an inside groove to provide clearance for burrs.
Steelex D3383 Precision Square is ideal for setup and inspection works. The heavy square ensures stability and precision when being used. Its compactness makes it easy to store.
Buy Now!Pros:
- Very affordable
- Precise and accurate
- Compact and portable
- Made of hardened, tempered, and polished steel for durability
Cons:
- Overall quality is relatively low
10. Faithfull FAIES4 Machinist Square 4″ Grade B BS 939
FAIES4 engineers square is the last item on this list of 10 best machinist squares. It is also affordable but worth the price and has high quality and accuracy to BS 939 grade B standard.
FAIES4 engineers square has a spring steel blade, which is hardened and tempered to make it more durable and accurate. The high-quality tool steel used in the construction gives this engineer’s square the best lifespan.
Spec:
- Grade: B (BS 939 standard)
- Blade length: 4″
Pros:
- Affordable
- Relatively accurate
- Durable and reliable.
Cons:
- Its squareness accuracy could have been better
Machinist Square Buying Guide
If you are familiar with woodworking and metalworking workshops, you know the features to look for in a machinist square. But for newbies, it can be challenging. This buying guide has tips to help you make the right decision.
1. Grades
Different grades of machinist squares exist, which tells you how accurate the tool is. What you choose depends on your specific application. Most machinist squares from the UK are graded according to BS 939, which defines three levels of accuracy. We have grade AA, grade A, and grade B.
Grade B machinist tools are accurate enough for most professional construction jobs. On the other hand, grade A is for laboratory and tool calibration works.
Source:
https://knowledge.bsigroup.com/products/engineers-squares-including-cylindrical-and-block-squares-specification/standard
2. Material and Construction
The material used in a machinist square determines its quality and reliability. Most are made of hardened stainless steel to resist corrosion and rusting. Additionally, they are ground and lapped to ensure parallelism and straightness for a long time. These are the best machinist square to buy as a long-term investment.
3. Dimension
Proper tool sizing makes your work easier. Machinist squares are not exceptional. Choose the right size that matches your workpiece to work more efficiently and accurately. Find the perfect balance – don’t make it too long or too short.
4. The Price Tag
You will be checking the price tag on each product before buying them. It depends on your budget, but mid-range or high-end machinist squares are preferred. But still, your decision should be influenced by the application. Buying a high-end tool for a relatively simple work that does not require much accuracy is uneconomical.
Square Comparison: iGaging Vs. Groz
The other machinist squares you want to check:
Conclusion
In terms of checking the squareness with a high degree of accuracy, the machinist square or we can call it engineer’s square as well is one of the best options available. It’s quick and relatively affordable. However, the disadvantage is it cannot tell you the error in number.
But, if you want to use it directly as the tool in your workshop, this is way more accurate than the wooden or pinned or rivet square out there.
We have reviewed the best machinist squares and included a buying guide in this post. So, which is the best or most recommended product to buy? It depends on the factors explained, but you can consider the following:
Groz SS/A2 Machinist Square is an excellent choice because it perfectly balances price and accuracy. Hobbyist and small workshops will like it. You can use it in many applications, and it is also very reliable and durable.
Accusize Industrial Tools Machinist Square is the second product we recommend for its high precision and ergonomic design. It is also relatively affordable and has a wooden case for safe storage.
Lastly, you can consider Moore and Wright Engineers Square. It is manufactured as a very accurate tool and is available in different sizes. It will give you great value for money.
You should keep one unit of machinist square in your workshop for verification, inspection, and calibration of your try square, framing square, double square, combination square, t-square, speed square, etc. Actually, any square tool you have should be checked frequently with a machinist square.