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Does your table saw leave burn marks on wood or produce smoke when cutting? Here are some of the most likely reasons why this happens and how to avoid it.
A good table saw with a proper blade should cut wood smoothly and cleanly without burning through it. But when the wood comes out of the table saw with burn marks like toasted bread, you know there is a problem. Sometimes the burning can happen along with a bit of smoking.
Why Does Table Saw Burn Wood?
A table saw can smoke or burn wood when the saw blade is unable to power through the wood effectively. In other words, when the blade experiences excessive resistance when cutting, friction builds up causing the blade to heat up and burn the wood fibers. Sometimes you might also see smoke or smell burning wood.
Reasons why a table saw heats up and burns wood
When cutting wood on a table saw, several factors can cause the saw blade to heat up and burn the wood. The 7 most common factors that you can easily control to reduce burning include:
1. Feed rate
Feed Rate is how fast you drive wood into the blade. It can influence the amount of friction that builds up on the blade when cutting.
A high feed rate inhibits effective dust removal. And when the saw dust accumulates in the kerf, it increases friction which in turn causes heat to build up and scorch wood.
On the other hand, a slow feed rate causes the blade to spin at one position on the wood for a longer time. This results in heat building up and subsequently burning the workpiece.
Therefore, pushing the wood too quickly or too slowly into the blade increases the chances of the table saw burning wood. You should drive the stock into the blade gently and safely with a push stick for best results.
2. Type of wood
The wood itself can also affect the way the table saw cuts. Some types of wood have oils or resins that get released when they heat up, which can cause them to scorch. Woods that have high oil or resin content like cedar, redwood, or pine are more prone to burning or smoking when cutting.
Another important factor relating to the type of wood is the wood moisture content. Wet lumber is more prone burning because the moisture increases the density of wood, leading to increased resistance when cutting. This causes heat to build up on the blade, resulting in the vaporization of moisture into steam and burning along the kerf.
Furthermore, wet wood or wood with a high amount of oils and resins makes the blade dirty and less effective.
The best way to ensure that wood is not too wet for woodworking is to use a wood moisture meter. The acceptable moisture content range is 7%- 19%. If the moisture content is higher, just leave the wood to dry or take it to the kiln dryer.
3. Blade quality
A poor quality blade does not cut effectively. It experiences high resistance when cutting which subsequently results in the build up of heat. This excessive heat causes the blade to burn through wood instead of cutting through smoothly.
Some factors that affect blade quality include blade sharpness, teeth alignment, the presence of dents on the surface, and the overall quality of the blade material. A dull saw blade or any blade with chipped or bent teeth will cut roughly and generate a lot of heat and smoke.
It is good practice to inspect the table saw blade to make sure the teeth are sharp, well-aligned, and not chipped. You should replace the blade if it has dents on the surface or a missing tooth.
Another important factor that affects the quality of the blade is dirt. A dirty saw blade cuts just as badly as a dull blade. You should always clean the saw blade after every project to remove gunk and pitch that may affect the cut quality.
In fact, most of the time you can restore the sharpness of a blade that seems blunt by simply cleaning it. As such, always clean the blade and test it before you conclude that it is dull and needs sharpening.
4. High-cutting speed
The faster the blade is moving, the more heat will be generated by friction. If the blade speed is too high, it can cause the wood to scorch. Similarly, if the blade spins too slowly, it will not clean sawdust from the kerf effectively. As a result, the blade may heat up and burn the wood.
The best practice is to not exceed the maximum RPM rating of the saw blade. Also, do not spin the blade too slowly such that it struggles to make a cut.
5. Misaligned fence
One of the most common reasons why a table saw blade would burn wood even when it is new is if the fence is not square. This is the straight bar on a table saw that keeps the stock parallel to the blade while rip cutting. The rip fence for table saw should be parallel to the blade.
When the fence is not true, it causes the stock to wedge the blade. As a result, the blade may experience increased resistance while spinning causing it to heat up and subsequently scorch the workpiece.
It is good practice to regularly measure the distance between the fence and the blade to make sure they are parallel. A fence that is true should measure exactly the same to the front of the blade and the back side of the blade.
Always use the blade as the reference point for setting the fence on a table saw.
6. Type of blade
There are two main types of table saw blades; cross-cut blades and rip-cut blades.
Crosscut blades are for cutting across the grain and have a higher teeth count per inch (TPI), which is good for making smooth cuts. On the other hand, rip-cut blades are for cutting along the grain of the wood and have fewer teeth for better sawdust removal.
If you use a saw blade with a high teeth count to rip lumber, sawdust may build up in the kerf, binding up the blade and causing it to heat up and char the wood. The best blade for ripping lumber should have 25 – 40 teeth.
When wood is cut with a table saw, it can appear burnt or scorched because of the high-speed rotation of the blade and the friction that is created between the blade and the wood. The friction can cause the wood to heat up, which can cause the fibers on the surface of the wood to be charred or burnt.
7. Underpowered table saw motor
Lastly, a weak table saw motor cannot drive the cutting blade through thick lumber without struggling. This may inevitably cause the blade to heat up and burn the stock. The motor may also produce a burning smell.
You should make sure that the motor on your table saw is powerful enough to handle the cutting needs gracefully. Otherwise, you will have to deal with ugly charred lumber and/or a burned out table saw motor.
How do you tell that a table saw motor is not strong enough?
Some of the telltale signs of a table saw with a weak motor include:
- The saw struggles to start or begins to stall frequently while in use.
- Difficulty cutting through thick or hard materials, even with a new blade.
- The blade does not rotate at its full speed without load
- The saw is unable to maintain consistent RPM and the blade slows down while in use.
- The amperage draw of the saw is lower than the motor’s rating. However, this test should be done by a professional technician.
There you have it. Those are the most common reasons why your table saw is burning wood and what you can do to prevent it.
To recap, always use good quality sharp blades and adjust the speed of the blade and feed rate to minimize the burning of the wood. Also, use the correct type of blade for crosscutting or ripping wood, and make sure the blade is clean.
Lastly, set the table saw fence so that it is square with the blade. But all these measures might not be so fruitful if the motor of your table saw is too weak to drive the blade through lumber effectively.
That said, if you take all these measures into consideration, your table saw will produce less heat, resulting in cleaner and more accurate cuts. And although sometimes you might not eliminate the burn marks on wood entirely, they will reduce noticeably!