Riving knife for circular purpose. Safety devices on a circular saw woodworking machine

When cutting boards along the grain, the teeth of the circular saw coming out from under the table can lift the board up and with great force throw it towards the worker. To avoid this, you need to wedge the board to be cut, or prevent the teeth in the back of the circular saw from touching both sides of the board to be sawn.

This can be achieved with a sword-shaped, sickle-shaped riving knife behind the circular saw (fig. 28). The outer side of the riving knife is 10% thicker than the cutting width. Gradually the knife becomes thinner to inside i.e. in the direction of the saw blade teeth. This shape of the riving knife ensures that the material to be cut is wedged and prevents it from being thrown into the reverse direction.

Rice. 28. Riving knife, fixed under the table: 1 - wedge, 2 - holder, 3 - square, 4 - square console, 5 - circular saw, 6 - nut securing the square, 7 - lamb.

The shape and dimensions of the riving knife must correspond to the diameter of the saw blade, its height above the table, as well as the cutting width. The riving knife must be reinforced so that it can be quickly and easily moved horizontally and vertically. The knife should be no more than 10 mm from the saw teeth. The height of the knife from its bottom edge should be 10 mm higher than the circular saw.

The upper guard of the circular saw serves to protect the worker's hands from collision with the saw teeth above the machine table.

Very practical and reliable is the Simson fence, shown in fig. 29.

The tube 3 is mounted on a stand (not shown in the figure) and can be moved vertically and set the fence to an appropriate height. A roller 5 is seated in the tube 3, which can move horizontally. It is secured with a clip 4. Top part The circular saw is fenced with a cover 6. To the front of this cover, a lever is attached to the suspension, along which the roller 8 can move when the sectors 9 are connected, which protect the working teeth of the saw. Back part saws (non-working teeth) protect two sectors 1. During operation, the front edge of the part presses on the lever 7, which, as it rises, picks up the roller 8 located between the front sectors 9 with its bent end.

As the part is fed, the roller 8 rolls up along the lever 7, and the front sectors 9 rise easily and smoothly, opening the teeth of the circular saw to a height corresponding to the thickness of the part being cut. The rear sectors 1 have teeth at the bottom, which prevents the piece being cut from being thrown back.

The saw blade's bottom guard is a suction device (see fig. 1) that removes sawdust. It shields the bottom of the saw blade (under the table).

If there is no extractor hood, for example in the case of a temporary installation of the saw, the saw blade is protected from below by a guard made of sheet steel... In this case, the possibility of removing the circular saw for a point and replacement is provided. A corresponding hole is left in the lower part of the guard to remove sawdust from under a running saw.

Stop for rip sawing.

Having perfectly aligned the saw with one of the edges of the table, I attached it with M4 screws. To do this, I had to drill the iron base of the circular in four places.

For installation on a table, in general, any circular is suitable, but if you choose the type of fastening with screws to the base, then it is better to choose a model with an iron base. Cast may crack.

There is another popular way to attach the circular to the table without drilling holes in the base - to attach it using clamps that fix the base, pressing it to the surface. Only this method seemed to me not correct enough in terms of the accuracy and reliability of the installation, and I did not apply it.

Another important parameter of the manual circular is the ability to connect a vacuum cleaner. If you cut without a vacuum cleaner, fine wood dust rises into the air.

The disc sawn through to the top of the tabletop. Height - 40mm (160mm Bosh wood disc). The table top reduces the cutting depth by 9 mm. The cutting depth is set on the circular itself. Conveniently, the disc can be completely hidden in the table.

UPD: IMPORTANT! On a number of budget circulars, it may turn out that the disc is tilted imperceptibly. And all the cuts will be chamfered. It is imperative to check with an instrumental square that the disc is at 90 degrees, relative to the table surface. (Before installing the saw, you can check the angle relative to the native site. perfect angle(you can use washers for the screws that secure the saw to the table, but this solution is worse)

I placed a saw socket inside the table, which will now be turned on by the start button.

This is how you can connect a vacuum cleaner to the saw. In general, the table is ready and can be cut. (made in one evening and one morning).

Sawing without equipment, of course, is possible using slats and clamps, but it is inconvenient.

This structure, pressing against the edges of the table and aligning with them, can move along the saw blade. Pressing the rail on the slide, you can easily saw it at exactly 90 o. Thin pieces of wood can be placed inside the sled.

You can even cut a slat like a sausage :) For example, I cut several pieces of different thickness.

Skids solve only part of the problem. For rip sawing, you also need a side fence.

I glued brackets from plywood that will cling to the edge of the table.

Grips the edges with a death grip.

A circular saw is a dangerous tool. In order not to saw off my fingers, I made from waste furniture board unpretentious pusher.

I have already managed to work with this table, sawed and slats, furniture board, plywood. It became much easier to carry out all these work than I did when sawing off with a hand-held circular saw.

In the future, I will further refine this table:
- I will redo the side fence for rip sawing so that, when moving, it always remains parallel to the blade
- I will put a removable riving knife to which the disc protection will be attached
- I will make a dust extraction from the top of the table. (Now, when I saw, the disc throws wood dust in my face)
- I will finish the improved pusher. I have already started making a more interesting and convenient version of the pusher, I will write about this in the future.

I will gradually implement this in the future, but for now I will work like this.

At detailed consideration you can find a lot of circular saws design features... Which of them should a novice user pay attention to?

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On the picture:

Characteristics

Power, blade diameter, cutting depth. The key characteristic of a circular saw is external diameter disk. This parameter determines the maximum cutting depth, and in addition, the speed and motor power (and hence the weight of the structure) "dances" from the diameter. The thickness of the sawing equipment also plays an important role. Some models are equipped with a thin-profile disc. It experiences less material resistance, which allows a less powerful motor to be installed.

Electronic systems

Electronic speed control few saws have it, as this option is rarely used (when sawing non-wood materials).

Soft start system designed to smooth the inrush current that can overload the network. In addition, the disc spins up smoothly, that is, there is no jerk at the moment of switching on.

Frequency stabilization system maintains the rotational speed of the disk at high level under load on the tool. Thermal motor protection will reduce power and then shut off the motor if the windings become excessively hot.

Electronic brake. Some models are equipped with an electronic brake, which significantly reduces the time that the disc runs out after shutdown.

Parallel stop

Facilitates straight sawing. Almost every circular saw comes with this simple device. It guides the tool along the edge and thus makes it easier to even cut... You don't even need to draw the markup. Such an emphasis does not guarantee an ideal straight line, but in some cases it helps out great. An example is the dissolution of boards into slats or bars.

Pictured: the GKS 190 Professional hand-held circular saw from Bosch.

Sole adjustments

Cutting depth adjustment. To set the minimum "overhang" of the disc teeth from the bottom surface of the board, the cutting depth is adjusted. By raising and lowering the saw body above the sole, you can set any value from zero to maximum. It should be added that the depth adjustment allows you to cut grooves.

Adjusting the cutting angle. Adjusting the sole tilt (from 0 to 45-50 degrees one way) is needed to cut at an angle to the surface, and is also useful when calibrating the zero angle of the disc. For convenience, the adjustment mechanisms are equipped with scales (millimeter and angular).

Sole Targets

Simplifies line guidance. There are pillars on the leading edge of the sole that make it easy to cut along the line without using stops. You do not need to look at the disc - keep the line at the desired rear, and the teeth of the rig will follow the markings. It can be noted that a number of advanced saws also have a special groove on the sole for the guide bar, which ensures a perfectly straight cut.

Riving knife

Protects against disc seizure. Many circulars have a riving knife, although not all. It is installed behind the disc and does not allow the sawn parts of the workpiece to close, which could clamp the rig and cause an increased load on the motor.

Package

Cardboard box or case. A circular saw is a rather bulky tool, so it is most often supplied in cardboard box, but some models come in a plastic case. Such packaging is more durable, because the cardboard becomes unusable over time.

Safety clutch

Protects against kickback. The jamming of the blade is accompanied by the so-called kickback, when the saw is literally pulled out of the hands. To protect the user from this dangerous situation, some circular saws install a safety clutch. If the disc is pinched in the array, this clutch will slip like a car clutch.

In this article, we'll show you some woodworking techniques for your home workshop. You will learn how to properly debug the circular saw so that it does not spoil the workpiece when ripping. The article contains techniques and tricks when working with longitudinal blanks.

The problem of burnt hardwood (oak, beech, birch) when sawing along the grain on a circular saw is solved only by grinding. And this is an additional operation, and quite time consuming. The appearance of scorch marks is a sure sign of incorrect setting of the machine, while the overloaded motor suffers, the disc is worn out and the workpiece deteriorates.

Most likely causes of burn marks

1. Resinated disc. Resin can be quickly removed special means or rinse off with regular solvent (this is a little longer).
2. Blunt or broken disc soldering. They can be restored, replaced or sharpened in a special workshop, but it is easier and faster to replace the disc with a new one.
3. Parallelism skew of limiters.
4. Incorrect feed of the workpiece.
5. Structural defects in wood.

The first two are relatively easy and quick to eliminate by cleaning or replacing the cutting blade. The other three are more serious and below we will tell you how to deal with them.

Reception of setting the parallelism of the disk and the stop by improvised means

1. Align the stop 100 mm from the disc.
2. Take a block with a length of 60-70 mm and screw a round head screw into the end. This head, when the bar is pressed against the stop, should cling to the disc tooth.
3. Mark this tooth with a marker.
4. Slide the blank with the screw to the other side of the disc and rotate the disc itself until the marked tooth is aligned with the head of the screw.
5. The force when the tooth engages the screw head should be the same at the beginning and at the end. This can be determined by ear - the metal of the disc perfectly reproduces vibrations. If the sound at the beginning and at the end is different, you need to more accurately set the saw device in accordance with the instructions (for different models, the methods will be different).
6. Professional models whose saws are stationary have workbench adjustment *. To do this, you need to loosen a few bolts (with which the workbench is fixed to the bed). Carpentry machines provide precise adjustment of the position of the saw unit.

* This refers to the part of the stationary saw, which is also called the "saw table".

Precise parallelism adjustment with hour indicator

This is a more professional and accurate method, but it requires a special device - the ICh-10 hour indicator. In this case, the reference point for the stop is the disc groove.

1. Install a rail or block into the groove.
2. Install the ICh-10 between the rail and the limiter. Then reset the reading.
3. Using ICh-10, adjust the stop according to the readings of the instruments - the difference in readings should be zero.

As you can see, this method is much faster and more accurate (graduation 0.1 mm), but such a device costs about 20 cu. e.

The trick when aligning the disc

The saw unit is always secured with several bolts. Therefore, when adjusting it, it is best to use one of them as an axis around which the entire mechanism or disc will move (by millimeters):

1. Select the "axle" bolt based on the location of your saw mounts.
2. Loosen it and then tighten it slightly more than hand tighten.
3. Loosen the remaining bolts carefully until they are free.
4. Set the mechanism or disc to the desired position, focusing on the readings of the ICh-10 or the alignment device.
5. Do not press on parts of the mechanism to move it, but tap on reliable parts- it will be more accurate.
6. After reaching the exact position, tighten the “axle” bolt first - this way the adjustment will not be knocked out.

This method is relevant for any stationary circular, reciprocating or band saws.

Riving knife trick

The final step in fine tuning the machine is to check and adjust the riving knife. This is a strip of metal behind the saw blade that opens the cut, preventing the pieces from being pinched. It must be strictly vertical and parallel to the disc. Parallelism is checked by the usual rule. For safety reasons, some models are equipped with toothed pressure plates - they prevent the workpiece from retracing (the disc rotates towards the operator). Their adjustment is reduced to checking the spring force.

Sometimes when wood has high density, the standard riving knife is not enough - the unfinished workpiece tends to return to its original position and there is a clamp behind the riving knife and inevitable burn marks. In this case, craftsmen use a simple solution that has no analogues in terms of simplicity and reliability: an ordinary spacer wedge on a leash.

Wedge for circular on video

How to make a spacer wedge:

1. After the workpiece has passed the standard spacer knife, insert a wooden wedge into the cut.
2. Next, make a full pass of the workpiece and fix the extreme position of the wedge.
3. Select a fixed point above the machine and match the leash in length from point to wedge. It is advisable to use a spring material.
4. Tie the leash to a fixed point (details).
5. After full passage the wedge will be removed from it and remain on the leash.

For convenience, when cutting many identical parts, you can adjust the length of the leash.

Correct feed of the workpiece

Marks and spoiled workpieces are the easiest consequences of incorrect workpiece feeding. Even well-set knives and stops will not help if the workpiece is not fed correctly - skewing, jamming, backward movement or uncontrolled jerking of the workpiece is very likely. Given the tremendous speed and strength circular saw even small light workpiece capable of injuring a person.

Correct filing rules:

1. Vertical clamp. No matter what angle you start the workpiece, remember that it must be firmly pressed against saw table at a distance of 30-100 mm from the disc.
2. Horizontal clamp. Tight contact with the stop will ensure the workpiece runs smoothly.
3. Wind and control the workpiece with both hands. This rule follows from the first two - one hand presses against the table, the other against the stopper.
4. For small parts make or purchase a pusher - it will avoid dangerous proximity of hands and saw blade.

1. Apply the "clamp-comb". This device is freely sold (price from $ 3), has many options. You can also make it yourself (especially if your circular is homemade) according to specific sizes. To do this, you need to make a lot of cuts in the bar and cut the "comb" at an angle of 75 °.

Of course, when working on machines, you should not be distracted or do other operations in parallel.

Structural defects in wood

Defective wood is usually discarded at selection. Working with such blanks is fraught not only with scorch marks (they will necessarily appear even on a precisely set machine), but also injuries. At the same time, the material can be clean, without rot and knots.

The main signs of structural defects:

1. Longitudinal curvature across the thickness of the workpiece. Craftsmen call such blanks "saber". If the curvature is small (the deflection height is up to 10 mm per 1 m), the workpiece can be pressed harder when cutting. Billets with a larger curvature are rejected.
2. Longitudinal curvature across the width of the workpiece. The popular name is "rocker". The rule is the same as with the "saber", but the allowable deflection is 20 mm.
3. The grain of the wood is not parallel to the workpiece. The most dangerous type of defect is that there are significant internal stresses in the workpiece. When sawing, they are released and it can behave unpredictably. The only option to use such a workpiece is to level it with a thickness gauge (double electric plane).

The first two cases can lead to burn marks, the last one will certainly lead. The sawn-off products of skewed wood will also have a curvature and must be in a relaxed state after installation.

Conclusion

Timely check of the machine will save you from the unpleasant obligation to remove burns and burn marks from the workpieces. Remember that all manipulations with the machine must be carried out after disconnecting it from the mains.

In this article, we'll show you some woodworking techniques for your home workshop. You will learn how to properly debug the circular saw so that it does not spoil the workpiece when ripping. The article contains techniques and tricks when working with longitudinal blanks.

The problem of burnt hardwood (oak, beech, birch) when sawing along the grain on a circular saw is solved only by grinding. And this is an additional operation, and quite time consuming. The appearance of scorch marks is a sure sign of incorrect setting of the machine, while the overloaded motor suffers, the disc is worn out and the workpiece deteriorates.

Most likely causes of burn marks

1. Resinated disc. The resin can be quickly removed with a special cleaner or washed off with a regular solvent (this is a little longer).
2. Blunt or broken disc soldering. They can be restored, replaced or sharpened in a special workshop, but it is easier and faster to replace the disc with a new one.
3. Parallelism skew of limiters.
4. Incorrect feed of the workpiece.
5. Structural defects in wood.

The first two are relatively easy and quick to eliminate by cleaning or replacing the cutting blade. The other three are more serious and below we will tell you how to deal with them.

Reception of setting the parallelism of the disk and the stop by improvised means

1. Align the stop 100 mm from the disc.
2. Take a block with a length of 60-70 mm and screw a round head screw into the end. This head, when the bar is pressed against the stop, should cling to the disc tooth.
3. Mark this tooth with a marker.
4. Slide the blank with the screw to the other side of the disc and rotate the disc itself until the marked tooth is aligned with the head of the screw.
5. The force when the tooth engages the screw head should be the same at the beginning and at the end. This can be determined by ear - the metal of the disc perfectly reproduces vibrations. If the sound at the beginning and at the end is different, you need to more accurately set the saw device in accordance with the instructions (for different models, the methods will be different).
6. Professional models, the saw of which is stationary, have a workbench adjustment *. To do this, you need to loosen a few bolts (with which the workbench is fixed to the bed). Carpentry machines provide precise adjustment of the position of the saw unit.

* This refers to the part of the stationary saw, which is also called the "saw table".

Precise parallelism adjustment with hour indicator

This is a more professional and accurate method, but it requires a special device - the ICh-10 hour indicator. In this case, the reference point for the stop is the disc groove.

1. Install a rail or block into the groove.
2. Install the ICh-10 between the rail and the limiter. Then reset the reading.
3. Using ICh-10, adjust the stop according to the readings of the instruments - the difference in readings should be zero.

As you can see, this method is much faster and more accurate (graduation 0.1 mm), but such a device costs about 20 cu. e.

The trick when aligning the disc

The saw unit is always secured with several bolts. Therefore, when adjusting it, it is best to use one of them as an axis around which the entire mechanism or disc will move (by millimeters):

1. Select the "axle" bolt based on the location of your saw mounts.
2. Loosen it and then tighten it slightly more than hand tighten.
3. Loosen the remaining bolts carefully until they are free.
4. Set the mechanism or disc to the desired position, focusing on the readings of the ICh-10 or the alignment device.
5. Do not press on parts of the mechanism to move it, but tap on reliable parts - this will be more accurate.
6. After reaching the exact position, tighten the “axle” bolt first - this way the adjustment will not be knocked out.

This method is relevant for any stationary circular, reciprocating or band saws.

Riving knife trick

The final step in fine tuning the machine is to check and adjust the riving knife. This is a strip of metal behind the saw blade that opens the cut, preventing the pieces from being pinched. It must be strictly vertical and parallel to the disc. Parallelism is checked by the usual rule. For safety reasons, some models are equipped with toothed pressure plates - they prevent the workpiece from retracing (the disc rotates towards the operator). Their adjustment is reduced to checking the spring force.

Sometimes, when the wood has a high density, the standard riving knife is not enough - the unfinished workpiece tends to return to its original position and a clamping occurs behind the riving knife and inevitable burn marks. In this case, craftsmen use a simple solution that has no analogues in terms of simplicity and reliability: an ordinary spacer wedge on a leash.

Wedge for circular on video

How to make a spacer wedge:

1. After the workpiece has passed the standard spacer knife, insert a wooden wedge into the cut.
2. Next, make a full pass of the workpiece and fix the extreme position of the wedge.
3. Select a fixed point above the machine and match the leash in length from point to wedge. It is advisable to use a spring material.
4. Tie the leash to a fixed point (details).
5. After full passage of the workpiece, the wedge will be removed from it, and remain on the leash.

For convenience, when cutting many identical parts, you can adjust the length of the leash.

Correct feed of the workpiece

Marks and spoiled workpieces are the easiest consequences of incorrectly feeding workpieces. Even well-set knives and stops will not help if the workpiece is not fed correctly - it is very likely to skew, jam, reverse or uncontrolled jerk of the workpiece. Given the tremendous speed and strength of the circular saw, even a small, light workpiece can injure a person.

Correct filing rules:

1. Vertical clamp. At whatever angle you start the workpiece, remember that it must be firmly pressed against the saw table at a distance of 30-100 mm from the blade.
2. Horizontal clamp. Tight contact with the stop will ensure the workpiece runs smoothly.
3. Wind and control the workpiece with both hands. This rule follows from the first two - one hand presses against the table, the other against the stopper.
4. For small parts, make or purchase a pusher - it will avoid dangerous proximity of the hands and the saw blade.

1. Apply the "clamp-comb". This device is freely sold (price from $ 3), has many options. You can also make it yourself (especially if your circular is homemade) according to specific sizes. To do this, you need to make a lot of cuts in the bar and cut the "comb" at an angle of 75 °.

Of course, when working on machines, you should not be distracted or do other operations in parallel.

Structural defects in wood

Defective wood is usually discarded at selection. Working with such blanks is fraught not only with scorch marks (they will necessarily appear even on a precisely set machine), but also injuries. At the same time, the material can be clean, without rot and knots.

The main signs of structural defects:

1. Longitudinal curvature across the thickness of the workpiece. Craftsmen call such blanks "saber". If the curvature is small (the deflection height is up to 10 mm per 1 m), the workpiece can be pressed harder when cutting. Billets with a larger curvature are rejected.
2. Longitudinal curvature across the width of the workpiece. The popular name is "rocker". The rule is the same as with the "saber", but the allowable deflection is 20 mm.
3. The grain of the wood is not parallel to the workpiece. The most dangerous type of defect is that there are significant internal stresses in the workpiece. When sawing, they are released and it can behave unpredictably. The only option to use such a workpiece is to level it with a thickness gauge (double electric plane).

The first two cases can lead to burn marks, the last one will certainly lead. The sawn-off products of skewed wood will also have a curvature and must be in a relaxed state after installation.

Conclusion

Timely check of the machine will save you from the unpleasant obligation to remove burns and burn marks from the workpieces. Remember that all manipulations with the machine must be carried out after disconnecting it from the mains.