Hand circular saw - a safe and dangerous tool

To the "family" of circular, or circular saws mainly include hand circular saw, miter saw and table circular saw - circular saw. The tool is a saw blade.

A bit of history

The first manual circular saw, similar to the ones we see today, was invented in 1923 by Edmond Michel and had a worm drive. It began to be sold en masse under the Skilsaw brand , so portable circular saws are still often called Skilsaw or Skil in some countries. Saw.

fig. 1 Skilsaw Model 77

Currently, the circular saw has reached perfection, especially in the field of professional saws. Its possibilities and design elements have not changed significantly for a very long time. Recently, cordless circular saws with rechargeable batteries have become popular. However, the difference between a table saw and a manual circular/circular saw is not only that one is stationary and the other is portable, the main one is in the way of cutting. When cutting with a hand-held circular saw, the material to be cut is usually completely horizontal in the vise and the saw is slowly moved along it. However, the table saw has a fixed position and the cut material slowly moves towards the blade.

Cutting takes place through the teeth on the perimeter of the saw blade, which divides the material by creating a groove. The teeth hit the workpiece in sequence, each tooth creating small chips with each impact. These are removed by the teeth of the saw blade. The cut has a narrow notch and a relatively smooth surface, the cuts are straight and precise, the saw usually leaves only small burrs on the cutting edge of metal and plastic . When cutting metal materials, we recommend using cutting oil.

Construction

The manual circular saw is " inflated " with mandatory safety features, which is fully justified in this case. It is considered one of the most technically demanding tools, even if we do not take into account that it can have a whole range of electronic " gadgets " at its disposal, mainly related to high-performance motors of electric circular saws. Therefore, high accuracy of arrangement is required during its construction, also mainly because of the cramped spatial conditions. Do-it-yourself circular saw repair is therefore considered quite risky.

fig. 2 Circular saw today

fig. 3 Circular saw and its main parts

1. Main switch
2. Safety switch
3. Top fixed cover
4. Lower movable cover
5. Base
6. Attachment
7. Setting elements

Where is the arrest?

The main switch does not have a latch where we would expect it. In other words – it has no lock... There is a safety switch at the place of the lock. Prevents accidental starting of the tool motor. When it is not pushed, it blocks the engine from starting. This is important, for example, when we walk with a saw in our hand and naturally hold it by the handle, where the main switch is within ergonomic reach.

Not having an arrest means having more security. It allows the engine to be started only by simultaneously pressing the main and safety switches. We don't have to worry about impractical control, good saws have both switches located in such a way that we can operate them simultaneously with the thumb and index finger, or with the index and middle finger - whichever suits better.

Electronics in the highest level of combat readiness

An example is the electrodynamic brake, which immediately stops the rotating disc when the main switch is released. The system is designed to protect the operator from possible injury, the workpiece from damage and the machine from kickback.

fig. 4 Start the engine with the index finger and thumb

One disc - two covers

The operator is protected from the rotating teeth of the disc by two covers. The upper cover is fixed and the lower one is movable with automatic position adjustment so that it covers the cutting disc as much as possible and thus minimizes the risk of injury during work. A spring presses it against the workpiece from the cutting direction and does not interfere during cutting.

However, the lower protective cover interferes with the need to make a plunge cut, so its position can be changed manually using a lever. However, holding the cover with one hand while cutting with the other requires considerable skill and must be practiced. For this reason, plunge circular saws are used for precise and safe plunge cuts.

There is no base like a base

The functionality of a circular saw depends largely on its base, as this is where all the mechanical adjustments and fixings of auxiliary elements are installed. The possibility of tilting it is essential - thanks to it, it is possible to cut at an angle. It is realized by changing the lateral inclination of the base in relation to the saw blade. The inclination is usually set at different angles: 30°, 45°, and in some machines it is extended to 50-55°, possibly even more.

fig. 5 Setting elements

In good circular saws, a mechanism for adjusting the depth of cut is also available on the base. Usually it's all in the form of grooves in the shape of a quarter circle , with a fixing lever, and mostly with a scale. The main advantage of quality control elements is that they are fast, reliable and accurate.

Part of the base and a good helper, especially for precise longitudinal cuts, is the attachment. Its position is usually adjusted with a separate lever and is usually removable. The bases are made of light alloys or steel. Traditionally, those made of light alloys are considered better, and somehow it was customary that they clearly indicate the professional class of tools.

However, even thick pressed steel bases have their advantages. Although they are heavier, they are also more resistant to impact loads - they do not crack in the event of an accidental impact, they have a lower price and are also used in some professional tools.

Other important elements

Among the elements that deserve attention are the handles, the suction flange, the possibility of arresting the spindle for an easier change of the saw blade, clearly marked cutting marks for straight cutting and for cutting at an angle, etc.

fig. 6 Cutting marks for straight cutting and cutting at an angle of 45°

Cordless circular saw and its use

Until recently, such machines seemed to us to be just a fantasy. Today's batteries are so powerful, engines so economical and chargers so fast that even a power-intensive tool such as a hand-held circular saw today also exists in a battery-powered version, and its popularity and utility value are indisputable.

You only need to take two powerful Li-On batteries with a voltage of at least 18 V and a capacity of at least 4 Ah, plus a fast charger , and you will have no problems with power supply. You work with one, the other is charging.

The power and torque of cordless circular saws today is comparable to similar mains powered machines. And when it comes to mobility and ergonomics, they are unmatched. They are especially loved by builders and roofers , who can work comfortably at heights without dragging long extension cables behind them.

Summary

The manual circular saw is mainly intended for direct cuts in wood and its derivatives, such as OSB, chipboard and fiberboard, plywood and the like. Also, cutting in ferrous and non-ferrous metals depends only on the correctly selected saw blade and, of course, on the power input of the saw.

The fact is that a hand-held circular saw is not nearly as versatile as a jigsaw or jigsaw, and it doesn't even cut arcs. However, it is a tool that perfectly holds the cut line. It has no competition in this, and this is also its main advantage – perfectly straight, straight cuts, even at an angle. That is why it should not be missing from the standard equipment of every craftsman.

Sources:
HERMAN internal technical and training materials
https://en.wikipedia.org/wiki/Circular_saw
Raj Pruthi (2004). Prehistory and Harappan Civilization. APH Publishing. p. 185. ISBN 978-81-7648-581-4.
Rebecca Kraft Rector (15 July 2016). The Early River Valley Civilizations.
The Rosen Publishing Group, Inc. p. 45. ISBN 978-1-4994-6328-6.
https://www.tool-rank.com/com/blog/first-generation-skilsaw-model-77-20100228897/

Ing. Herman Nagypál

I graduated from a military school. I learned to work with tools and equipment as a child with my father on the construction of our family house. I test each of our new products personally - with my own hands in my well-equipped workshop. In my spare time, I study trends in the field and like to try competitive products. Some of them make me laugh, and some of them make me wonder (that someone got caught and bought it), but some are really good. Almost like ours 😊.