Monday, March 15, 2010

The Table Saw: Heart of Any Fine Woodworking Shop

          There are many things you will want to consider before purchasing a new table saw for your shop. There are three main types of table saws: (1) the lightweight, inexpensive and portable contractor’s saw, (2) the cabinet saw, so-named because it has an enclosed cabinet as opposed to open base and (3) the new breed of so-called “Hybrid” table saws which fill the price gap between contractor’s saws and cabinet saws. This discussion will be only concern cabinet saws because, in my experience, nothing less will do for a shop that produces fine woodworking. Smaller saws lack both the accuracy and capacity of cabinet saws.


          The table saw is the heart of your shop. You will use it more than any other machine and its accuracy and capacity will determine the quality and size of what you will be able to produce. This is akin to picking someone to marry: Ideally, it’s for life and you will have to live with your decision for a long time to come. Therefore, rushing into purchasing the first table saw you see, without doing your homework, is like a quickie Las Vegas marriage, always a gamble.

          There are many things you should consider before you should consider before investing your hard-earned dollars in any particular machine. As I have said again and again, any woodworking machine you buy should be just slightly more capable than what you will demand of it now or what you imagine you would likely to demand of it in the future. While price is important, affordability should not be the sole determining factor in your purchasing decision. If you can’t afford the saw you need, wait until you can. Don’t saddle yourself with a table saw that may drive you crazy every day of your life. Take a few moments to consider what you really need and which machine will best fill the bill for you.

          I’d like to take a minute to talk about the features that you should be looking for and what these features will mean to you after you unpack and set up your new table saw. These features include: motor horsepower, blade size, trunnion construction, tabletop flatness, tabletop size, arbor size and arbor bearings, sawdust extraction, ease of operation including raising, lowering and tilting the blade, tilt of the blade (left or right), the necessity of a magnetic switch and the importance of its location, ease of access to the interior of the cabinet, accuracy and ease of operation of the fence, the amount of rip space to the right and the left of the blade, safety features and table saw mobility around the shop. In addition to the table saw itself, you may want to construct an outfeed table around the back of the saw, if space permits. We’ll talk about that, as well.



MOTOR HORSEPOWER

          Motor horsepower and blade size are closely related. The larger the blade, the more horsepower you will need to cut, at full blade height, through a piece of wood. Too much power is never a problem. Too little power can cause the saw to bind, slow down and even stop in the middle of a cut. This is not good, nor is it safe.

          The smallest motor I would even consider for a 10-inch saw would be 3 horsepower. For a 12” to 14” saw it would be 5HP and for a 14” to 16” saw, I’d like 7.5 HP. You will also need to consider if the saw motor is single or three phase. Three phase motors use electricity a bit more efficiently. If you don’t have three phase power at your location, however, you will either have to buy single phase or purchase and install a phase converter large enough for your saw motor. Most saw motors use 230 or 460 VAC power, so make sure you have available in your shop the voltage your saw will require. Three phase motors can run on 208 to 220 volts or higher, depending on the motor.



THE TRUNNION


          The trunnion is the mechanism inside the cabinet which is responsible for both raising and lowering the blade and tilting the blade for bevel cuts. It is controlled from the outside of the saw by two separate wheels or cranks: one for raising and lowering the blade (usually found on the front of the cabinet) and the other for tilting the blade (either left or right, depending on the saw) which is usually, but not always, located on the side of the cabinet.

          The trunnion determines the accuracy of your cuts so you want to be sure that it is well built and accurately machined. The saw blade must always be exactly where you need it to be. Furthermore, the trunnion must be easy to operate. It should not require Superman to raise or tilt the blade. As time goes on, you may find that it is harder to turn the wheels or cranks that operate the trunnion. This is usually because of sawdust contamination of the gears and/or lack of lubrication. Some better saws have ways of eliminating sawdust from the cabinet into an external dust port before it can get into the gears. Other saws come with self-cleaning gear teeth.



TABLE FLATNESS AND SIZE


          One table saw manufacturer I know believes in “aging” its cast iron machine table tops before milling them flat. The tops are cast and then left outside in a “bone yard” to bend, bow, warp and twist in the sun and rain for a year or so. Then, they are brought inside where all the rust is removed and the table top is ground absolutely flat and polished to sheen. The theory is that the metal needs to settle into a place where all post-casting movement has ceased and that the table should not be ground flat before this is done. Otherwise, the table may move out of absolute flatness after it is part of your new table saw and that it not at all desirable. Why? Because the flatness of your table saw top will determine the accuracy of your cuts. Be sure to check your new table saw for table flatness with a straightedge on or before delivery and afterwards from time to time. Lay the rule across the table top at all angles and check for daylight under the rule or rocking of the straightedge on the table top.


          The size of the cast iron table saw top is also important: the larger the better. When you are sawing large objects, you want as much flat table surface as you need to support the work piece flat to the blade for accuracy. Larger table size is usually accomplished by attaching cast-iron table wings to the edge of the main table. These wings must be as flat as the table and the seam they create must be aligned so that the top of the wing is flush to the table saw table along its entire length.



ARBOR SIZE AND ARBOR BEARINGS

          The saw blade is mounted on an arbor with an arbor nut and the arbor is turned by the motor usually via pulleys and 1 to 3 V-belts. The arbor is mounted into the trunnion inside two or more arbor bearings. These should be sealed from dust for obvious reasons. The size of the arbor determines the size of the hole in the middle of the saw blade. This is usually 5/8” for a 10” blade and 1” or larger for blades larger than that. The strength and alignment of the arbor and the bearings which support it determine the accuracy and smoothness of the table saw. Vibration and noise should be kept to a minimum and the saw blade should be straight in the table from front to back at all elevations and bevel angles.



BLADE TILT


          Most table saw trunnions are made to tilt either left or right (but not both) to a maximum of 45 degrees from vertical. If you have a choice, and you usually do, never buy a right-tilt saw for the following reason. A right-tilt saw tilts the blade towards the fence and can pinch a work piece into the fence, causing a jam or, worse, a kickback just as the cut is finishing. Further, on a right-tilt saw, the blade is tilting towards the fence and could cut into and ruin it if the fence were to be inadvertently moved too close to the spinning blade. A left-tilt saw tilts away from the fence and instead of pinching the work piece, allows it to rise vertically slightly, if need be.



KICKBACK AND PERSONAL SAFETY


          There is a rule that says, “Never stand directly behind a horse or a table saw.” Sooner or later every table saw operator will do something stupid that causes a kickback. If the operator makes it a practice to avoid standing where the kickback will occur behind the blade, he or she will probably avoid the severe injury that can be inflicted by a flying piece of wood striking the face, neck, chest or arms of the woodworker.


          There are many hold-down and anti-kickback devices on the market. Some are good and some are a hazard in themselves. I had a large metal combination hold-down and anti-kickback device get caught in the saw blade, ripped off the fence to which it was clamped and flung into a plate glass door behind the saw. I heard it go whistling past my right ear. It missed me because I was standing, as always, well to the left of the saw blade.


         Woodworking can be a dangerous business. Always use a push stick or similar device. Fingers are not replaceable. Never try to rip narrow strips next to the fence. Instead, cut them off of the left side of the work piece. In this case, you would stand to the right of the blade. In short, think ahead about the possible complications of what you are about to do, keep your eyes wide open (wearing goggles, of course) and keep your wits about you at all times.

          Another important safety device is the magnetic switch. This device protects you after an electrical power failure. If the power fails and you have a regular switch, the saw will come back on when the power comes back on. If you were to be near the blade at the time, this could be disastrous. A magnetic switch will not allow the saw to start again until you press the button. The location of the switch is also important. It should be right out front where it can be quickly accessed by a hand, foot or knee in the event of an emergency. The off button should be wide, red in color and should extend outside of the switch box like a mushroom for fast access.



SAWDUST EXTRACTION

          My ideal would be to never have a speck of dust reach the gears of my table saw trunnion and that all sawdust would be sucked away from the saw blade and out of the machine as soon as it was made. I would never need to clean out sawdust from inside the saw cabinet and the trunnion would always operate smoothly and easily. While I don’t expect to ever see my dream fully realized, there are saws on the market today that closely approach this level of efficiency in sawdust extraction.

          Some saws shield the blade in a casing underneath the saw table and suck the dust out directly from there. Others slant the floor of the saw cabinet towards a dust collection port. Many just allow the sawdust to accumulate on the floor under the saw until you clean it out. You will always have some cleaning of the interior to do. Perhaps you won’t wait until the sawdust has totally encased the trunnion gears packing itself up to the bottom of the table top. You will need to connect the saw to a dust collector through its dust port. The suction of the dust collector should be about 350 CFM for a 10” saw and more for a larger saw.



CABINET ACCESS


          At least one, but preferably two or more access doors should be provided leading into the cabinet of the table saw. The one you will use most often will be for cleaning out the interior of sawdust. Another should give easy access to the motor, trunnion and belts for adjustment and repair. Many saws provide a removable access panel instead of a second door. That’s fine for occasional motor, arbor, belt and trunnion access but you will want the sawdust door to open and close easily.



THE FENCE

          The saw should come with a Biesemeyer or similar type fence included in the purchase price. This type of fence locks and aligns itself to a rectangular tube attached to the front of the saw table when you press down on a handle. Fence accuracy and ease of operation will be important every time you touch your table saw and so a cheap fence is no bargain. The fence will probably read measurements along a stick-on measuring tape on the top of the front fence rail tube. You will need to carefully adjust the fence for accuracy. Instructions of how to do this should come with the set-up instructions for the saw.

          The fence must be aligned so that the front of the blade and the rear of the blade are exactly the same distance from the fence at all settings. Once you have ascertained that the blade and fence are parallel to each other, you must cut some test boards to accurately set the fence to the scale. Set the fence to exactly 2” on the measuring scale. Rip a test board and measure it. Adjust the fence to the scale by moving the viewer’s hairline left or right. Rip more boards until you have exact accuracy. The viewer through which you see the tape should be strong in magnification.



RIP CAPACITY


          Your new saw must have a rip capacity equal or wider than the widest thing you will ever want to rip. Usually, a cabinet saw will have a rip capacity of around 30 inches or 50 inches. A large rip capacity to the right of the blade will require an extension table to support work wider than the cast iron table. Many times, this extension table is included with the saw or, alternatively, you can easily build you own. The fence must have a tube or rail long enough to achieve the maximum with you want to rip.


          If you consider that a sheet of plywood measures 48” in width, I would think that you might want to opt for a 50-inch rip as opposed to the slightly less expensive 30” rip capacity. You might want to rip off only one inch from that sheet of plywood and, while doing that, you will want the plywood to be fully supported. You might want to crosscut a sheet of plywood into two 48” pieces. You also should consider the rip space to the left of the blade: The wider, the better. Sometimes, you might want to accomplish tasks that require the fence to be put over to the left side of the blade.



TABLE SAW MOBILITY


          Some shops are small enough to require that all machines be able to roll around on the floor. The theory is that you pull out only the machine you are using at the time. In planning your shop, you should decide if your space requirements will mean that everything has to roll, some machines but not others have to roll or all machines can remain in their own positions permanently. Many cabinet saws offer the optional extra of some sort of mobility device. In the case of a table saw, you don’t want it rolling around while you are pushing lumber through it and so the wheels must retract enabling the saw to rest on its cabinet base on the floor.


          Some of the nicer table saws have the caster wheels permanently mounted inside the cabinet so they are never seen and are never in the way. A foot pedal controls raising the saw up into the mobility position and then lowering it back down onto the floor. If your table saw does not have this feature, after-market mobility bases can be purchased as needed.



BUILDING AN OUTFEED TABLE


          The ideal solution is to have enough shop space so that you will never have to move your saw around at all. In this situation, you can construct an outfeed table to support large work pieces and long lumber as they leave the back edge of the table saw table. Ideally, depending on space available, you should build this outfeed table so that it extends eight feet or more in back of the blade. You can use the space underneath the table for lumber storage and/or drawer space. The table can also serve as a work bench for the construction of large cabinets and tables. You can use it for pipe clamp glue-ups and spray painting layout, as well.

          Needless to say, the table must be exactly the same height as the top of the table saw table and you may need to extend the slots for the miter gauge into the beginning of the top of the outfeed table. If your saw extension table extends 50 inches or so to the right of the blade, so should your outfeed table and it should extend along the entire back edge of the table saw to the left of the blade. The saw should ideally be oriented so that you can bring long lumber through the shop door and directly onto the saw table without having to turn a corner.


          If you keep what you have read here in mind, you should be able to find a machine that is perfect for your needs. Remember, cheap price guarantees neither satisfaction nor success.


Bob Gillespie

Woodworker

For similar articles and tool reviews see:

http://www.perfectwoodworking.com/




© 2010 Robert M. Gillespie, Jr.

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