Rip-cutting circular saw blades are manufactured to cut with the grain of the wood. The blade characteristically has a wide gullet, aggressively positive angle hook, fewer teeth than any other saw blade type. The main purpose of such design is to rapidly rip the wood without grinding it, and easily get rid of waste such as sawdust or chipped lumber. Rip cutting or simply “ripping” is cutting along the fibers of the wood, not across, meets less resistance of the stock and splits it very quickly. Circular saw blades designed for this type of cutting vary greatly from saw blades designed for crosscutting. Most of those differences come from the fact that it is easier to rip than crosscut, meaning that each tooth of the blade can remove a larger amount of material.
The best type of saw for ripping is a table saw. The blade rotation and table saw fence help to control the wood being cut; allowing for very accurate and fast rip cuts. With the right blade, hardwoods can be ripped as thin as 1/8”. Radial arm saws are not as good for ripping, as the blade rotation tends to lift the wood off of the table, creating the potential for an unsafe situation and damaging the wood on the sides of the kerf. Ripping is always accomplished against the rotation of the saw blade; allowing the rotation of the blade and the bite of the teeth to force the wood down onto a table saw’s table. If one were to attempt to cut with the direction of the blade rotation, the blade could grab the wood, lifting and propelling it forward as a missile. Wood that is grabbed in this manner can easily go through the wall of a workshop.
Rip cutting circular saw blades typically have a large positive rake angle, helping to ensure that they get an aggressive “bite” into the wood, removing larger chips on each pass. A rake angle of 20 degrees is not uncommon. Positively angled rake, next to large gullets, are set in order to increase the feed rate. Side clearance angles are adjusted to get rid of large amounts of wood.
Blade teeth are often flat-top ground (FTG) as splintering and splitting is not much of an issue. Simple FTG shape offers good durability and efficiency, as these characteristics are prerequisites of a successful saw blade. The small flat chisels on a rip saw blade that slice parallel to the grains easily become blunt, since the actual surface of the wood they cut is absolutely non-comparable to the crosscut saw blades. Some rip cutting blades alternate the standard FTG teeth with a modified tooth, which has the corners knocked off at a 45 degree angle. This combination of a shorter FTG responsible for removing sawdust, and higher, but corner-less shape is TCG pattern. TCG blades are designed for longer life, as the tooth without the corners can cut the center part of the kerf, allowing the teeth with the squared corners to clean out the corners of the kerf. It’s a perfect choice for rip-cutting any type of wood. For this application even combination saw blades with ATB design, but lower teeth number, can be a good purchasing option.
To accommodate this larger “bite” of the wood, rip cutting blades have less teeth, typically only having 18 to 36 teeth. The number of the teeth can be even higher, depending on the saw blade diameter and tooth design. The tooth count for TCG shape is around 30, 40 to 60. The gullet is considerably larger, in order to accommodate the larger quantity of chips and sawdust that accompany faster cutting. A major concern is the blade’s ability to expel the wood chips, preventing binding and the subsequent overheating.
Plate Materials and Coatings
Rip cutting blade plates are made from stainless steel or high speed tool steel (HSS); a ferrous metal with alloys of chrome-vanadium or cobalt. The saw blade won’t tear-out or become warped so soon if it’s made of quality steel like HSS, having tough physical properties, and especially if teeth are coated with protective layers. They are typically carbide tooth blades, for high durability and longer life expectancy between sharpening. Tungsten carbide tipped blades are considered as premium quality saw blades.
Finish, Dimensions and Safety
Due to the low tooth count, ripping blades do not provide for a smoothly finished cut, regardless of the material being cut. It is necessary to finish off the cut with a plane or electric sander, if sanding is required for further treatment. For this same reason, they are not good for crosscutting. When used for crosscutting, the low tooth count and high rake angle will make the blade try to pull through the wood too quickly, causing damage and poorly finished, rough cuts. The usual carpentry jobs include cutting moldings, which generally must be done very precisely, according to the length and thickness. Rip cuts should be done with thin-kerf blades in this case to define dimensions properly. Watch out for this label when buying a circular saw blade. The biggest problem you can expect is a nail in a plank, which can seriously damage the blade plate and prevent its further use for demanding jobs. Circular saw will more likely hook it when ripping that cross-cutting. A nail could not only crack the saw blade plate, but damage the circular saw while revolving or seriously injure a worker. Woodworking with electrically-powered machines like circular saws requires caution and wearing carpentry safety equipment for your own good.
Vibrations and Kickback
Vibration and flexing is a major issue with these blades, as the blade will naturally try and follow the path of least resistance. This can cause a blade to try and wander to one side, following the grain. To combat vibration, vibration dampeners are often cut into these blades. Many ripping blades are designed with an anti-kickback feature, to provide maximum comfort and safety while working. This is a rise in the blade plate, behind the shoulder. In a kickback situation, the wood typically rises off of the table, moving back away from the saw blade. In the process of moving back, the kickback point (which isn’t sharp enough to cut) would bottom out in the kerf, causing the wood to drop back down to the table, thereby ending the kickback.