Many woodworkers consider circular sawblades to be the most complex of all the cutting tools. Available in a number of sizes, the steel discs have a number of shaped teeth around the periphery and a hole in the centre to fit a machine drive shaft.
The teeth of a circular sawblade give it it's distinctive capabilities. The teeth are brazed to the trailing edge of the gullet and are designed to perform a range of cutting actions on a variety of materials. Each blade incorporates a specific tooth style, gullet, tooth angle and is designed specifically for a specific function. For instance a woodworker should not use a crosscut blade to rip wood and a ripsaw blade should not be used to make a crosscut. Doing so is not only inefficient, but also dangerous. In general, blades with more teeth give a smoother cut, and blades with fewer teeth remove wood faster. Crosscut saws usually have more teeth than ripsaws.
Sawblade performance considerations
The sawblade by itself has very little lateral strength, most of its power comes from the force exerted by the speed of the saw teeth. A 250mm diameter sawblade on a machine spinning at around 4,000 rpm travels at a speed of around 190 kmph at the tip. A considerable amount of heat is generated at this speed by the friction of the teeth as they slice through the wood. The heat generated is also dependent on other factors such as the condition and type of blade, the wood being sawn and the moisture content of the wood. While the centre of the blade will have a temperature of around 80 degrees Celsius, the periphery of the blade can have temperatures of around 400 degrees Celsius. The saw body has expansion slots built into the saw body, which allows the blade to expand at the outside.
Bore tolerance is another important aspect that woodworkers should be aware of when using circular sawblades. The sawblade is not perfectly round when you cut. It is not possible to exactly fit a 30mm bore sawblade onto a 30mm spindle and there is always some small difference to allow the blade to fit. To minimize the difference, the bore of the sawblade must be as close to the spindle size of the machine as possible. Any larger difference will result in the blade running out of "round" so that only a few of the teeth cut effectively. To fit a 30mm bore sawblade to a 20mm spindle, you can get a sleeve to take up the difference, but every little variation will add up to poor performance.
Noise is a factor that woodworkers cannot ignore. Noise is created by the movement of air at high speeds. It can be reduced by the design of the saw gullet and by adding laser cut grooves in the body of the saw-blade or by a dampening treatment. The cheaper option are laser-cuts provided on some good quality blades. Crosscutting blades are noisier and more prone to dampening.
Maintaining your circular sawblades
Woodworkers can increase the efficiency of their sawblades by as much as 15% with proper maintenance. Proper maintenance can result in saving power required to drive the saw through wood and also a reduction in the operating temperature of the saw tip. Organic acids are claimed to contribute towards saw blade steel corrosion, and it is important to clean the blade regularly. Also the gullets, if clogged will increase the tendency for the sawblade to crack from the gullet base.
Keeping the blade sharp ensures that it always operates at peak efficiency. A dull blade will wear out faster and will not cut as efficiently. Woodworkers should also remember to never run the blade after it gets burnt as sharpening an overly dull blade require removal of a larger portion of the cutting material than necessary for superior performance.
Sawing is a primary machining function in the woodworking shop and circular sawblades are the main sawing tool. To get the best from circular sawblades. Woodworkers will do well to remember to use the correct blade for their project, maintain the machine in good condition and use safe sawing practices to get the best out of the machine for a number of years.
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