Engineer Square Vs. Combination Square

Like many other squares, engineer square and combination square can help you establish the right angle, squareness, and perpendicularity. But, they are comparable to doing a certain job.

The core difference between engineer square and combination square is accuracy.

The engineer square or machinist square is the most precise square among the square models available. The squareness is off for a small number only. Therefore, it’s reliable to use when you require high precision such as in precision miter join. In contrast, because the combination square’s head is adjustable, the accuracy is not that reliable. It changes as you slide it. Even, you need to check it before using it. Getting worst, wear and tear can cause greater inaccuracy.

This post is interesting. We are discussing how the engineer square and combination square are different from how how they look like until their applications. Hope this post helps you to decide which one is suitable for your project.

Engineer’s Square (Machinist Square)

1. Accuracy

Engineer squares stand out in terms of squareness accuracy. They come in grades that indicate their accuracy. Therefore, due to their accuracy, the engineer squares are used as a standard in the workshop or calibration lab. But, the low-cost ones may be suitable as a working tool rather than a standard in your workshop.

2. Shape (Body Shape)

The shape of the square is like a try square which forms an L shape. However, a typical engineer or machinist square doesn’t have any rivets or pins to conjunct the blade and stock. That is why it will not wobble. They are totally one-body construction.

A small vacancy or notch is present at the inside corner which is designed to collect small particles of debris. If that debris is collected at the inside corner without the notch, it can disturb how you check squareness properly.

However, you can find the engineer square come in the shape of a total square such as this Mitutoyo 311-111 (#affiliate link). So, it’s not an L-shape. It’s a square.

3. Material

Both the blade and stock are made from the same material. They are made from steel since it’s durable, more heat expansion resistant, and provides long-term integrity.

4. Working

There are no scribing guide holes, no markings, etc. The one thing that we take advantage of in this tool is its accuracy. Simply, we can use it directly. You can use its internal or external corner to check perpendicularity or squareness.

Put the stock and blade of the engineer square so that they stick on the object’s edge. In some cases, you may need a flat surface such as a workshop surface plate to work with this square. Put the blade on the surface plate, while the blade touches the object to check. If there is no gap between the blade and edge, then the angle is 90 degrees.

Any model of feeler gauge may assist you to measure the thickness of that gap. Make sure to use the best feeler gauge for greater accuracy.

5. Applications

The popularity of the engineer’s square comes from its accuracy. It is mostly used by metalworkers, but woodworkers who require high precision also incorporate it to confirm inside and outside 90-degree corner angles. Most importantly, the engineer’s square is used in complex projects where the accuracy of squareness is critical.

Combination Square

1. Accuracy

Combi square has less accuracy squareness compared to engineer or machinist square although it provides more flexibility. As far as we know, they don’t come with a squareness grade. But, the information about the blade straightness may be available when you purchase it.

2. Shape (Body Parts)

A combination square consists of a rule and a head/stock. The head is attached to the ruler. These are the standard parts. In some models, the protractor head and center finder come as additional features that are attached to the rule. These two additional attachments add more versatility of function to the combination square.

So, if you buy the complete one, you will get a combination square with these body parts: ruler, head, lock, spirit level, protractor, and center finder.

The head allows you to establish 90 and 45 degree angles; only those two angles. It also has an integrated spirit level for levelness checking.

The protractor head can be used to not only measure 45 and 90 degrees but also any possible angle in the range of 0 to 180 degrees. Some protractors can rotate reversible, while some cannot. The brand that produces various different models of a combination square is Starrett. So, don’t forget to check their products if you need the best ones.

There are graduation markings on the rule for taking linear measurements. You may need to check the graduation accuracy before trusting it.

3. Material

Different body parts may be made from different materials.

The rule is made from steel (stainless steel or hardened steel) but the lock bolt is made from brass. Cast iron is the material for the head. Other attachments may be made from plastic. It’s very comparable to engineer square which has a single material only.

4. Working

The head of the combination square can be attached or detached by sliding the rule into a slot in the head. There is an adjustable bolt that is used to lock the head in position while transferring a measurement from one object to other. To move the head to the desired length, loosen the bolt.

5. Applications

It can measure depth, height, length, width, and angles. The center finder head can mark lines through the center of a circle or square object. Moreover, the protractor helps you measure a corner with ease. But, the protractor only serves 1 degree resolution. If you need a more accurate protractor, you need a vernier bevel protractor.

A combination square can be used for multiple purposes like measuring, layout, marking, and referencing perpendicular and 45-degree angles (Standard Head). Both the spirit level and the ruler straightness can help you determine a working surface that is level and flat.

All of these functions make it appropriate to use in carpentry and woodworking projects.

But, using the combination square can slow down your work if you only have a single tool of this, meanwhile, you are going to use it for many functions, which makes you have to always adjust the heads all the time.

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