Friday, August 8, 2014

V5.32 - Table Saw: Drives and Fences

Ok, back to the mission at hand - Mr. Table Saw. We had introduced the Table Saw and left off talking about how the motor is connected to the arbor. One thing I might mention, there are several table saws that use a ‘universal motor’ (this motor has brushes inside it, just like your electric hand drill) and some of those motors have a cogged drive belt inside the motor unit. (most of them have reduction gears, not a belt) This gives some folks the opportunity to claim that the saw is a ‘belt-drive’ saw and cheat unsuspecting buyers. Now, technically, they are correct, but in the world of table saws, a universal motor that uses a drive belt is NOT the same thing as an induction motor, with a v-belt and pulley drive system.

Ok, to continue our saw drive information; the v-belt and pulley drive system has certain advantages over direct-drive systems. For instance: A- the maximum thickness of wood that can be sawed is greater, because it is not necessary to keep the motor down to allow for motor clearance under the table. All that is needed is room for the arbor pulley and that is a lot smaller, so the arbor itself can get closer to the bottom of the table - therefore, the blade can cut deeper. B- It is easier to change from one motor to another in case of motor failure or in case the saw is transferred from one shop to another with a different power supply. C- A belt-drive saw does not coast as long as a direct-drive saw when it is turned off. This adds to the safety of the belt-drive saw. D- Problems with the saw motor or drive system are far easier to troubleshoot on a belt-drive saw. E- If the saw motor is a true ‘direct-drive’, meaning the blade is mounted directly on the motor shaft AND the motor is an induction motor, it will be a quieter running saw. But if the motor is a ‘universal motor’ with a gear reduction drive, it will be much, much louder. The belt-drive saw is almost as quiet as the direct-drive.  

There are two methods of accurately guiding the workpiece past the blade: a rip fence and a miter gauge. The rip fence is usually guided by, and mounted to bars that are fastened to the front and rear edges of the table. On some smaller saws, the rip fence is mounted on the table edge itself. In either case, the front rail or front table edge will have graduated markings that tell how far the rip fence is from the blade. The rip fence is used for all ripping operations and is secured during sawing operations by lock knobs or clamp handles.

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