It's one thing to own an expensive sports car or a luxurious boat, it's another thing to keep it in top condition over time. Regular maintenance is essential to keep all of our "adult toys" operating at their best. A table saw - or any power tool - is no different. A well-tuned machine is a pleasure to use, while a poorly maintained one is at best inaccurate and a pain to use and at worst can cause a serious accident.
Keeping a table saw in top-notch condition isn't difficult, it just takes a bit of attention in the form of regular maintenance including cleaning, inspection, replacement of worn parts, alignment and fine tuning. I like to go over my saw and perform each of the operations I've described in this column at least once every six months - more often if I'm using the saw all the time. It's also prudent to go through most of these procedures on a brand-new saw right after you assemble it. Good maintenance will keep any kind of table saw - cabinet, contractor's or portable - performing both accurately and safely over the decades to come.
Cleaning the Guts
Sawdust builds up on a table saw's mechanical components, like the trunnion sector and worm gears, angle stops, and the mechanism that raises and lowers the blade. Sawdust and gunk tend to make adjusting the saw sluggish and can even lead to inaccurate settings, say when returning the saw to square.
Start by unplugging the saw from power and take off any dust collection hoses or catch bins from the saw's base. If it's not too heavy, carefully tip the saw backwards and rest the back edge of the table on a pair of sturdy boxes. (With contractor's-style saws, use boxes tall enough to keep the saw's motor from contacting the floor.) Lighter portable saws can be flipped over onto their tops. Inverting the saw makes cleaning a lot easier than trying to reach up underneath and have sawdust fall in your face!
To loosen dust and oily gunk that have built up and caked on mechanism surfaces, scrub the parts with a brush that has either firm nylon or medium-stiff brass or steel bristles. To get greasy dirt off the saw's trunnion and gear teeth, you may need to dip your brush in a non-flammable solvent degreaser, such as LPS T-91. Pry gunk that's trapped in narrow slots and cavities with a thin wood stick or narrow screwdriver.
Next, use a strong shop vacuum to suck up the debris from all surfaces. Vacuuming is preferable to using an air hose, as high-pressure compressed air simply blows dust all over the shop, where you'll have to clean it up again. To help get into hard-to-reach spots, fit the end of the vac's hose with a crevice tool. While the saw is inverted, you should also vacuum the saw's motor housing and electrical switches and junction boxes. Fine dust built up in these areas can actually ignite from a tiny spark and cause a shop fire.
Lubrication
Once the saw's internal mechanisms are clean, it's time to lubricate them, so they'll operate smoothly and make adjustments easier. Since the inside of a table saw is constantly bombarded by flying sawdust, never apply wet lubricants, such as greases, oils and non-drying sprays like WD-40. Sawdust sticks to these compounds and eventually gums up the works. Instead, coat the saw's trunnions, gears, screw threads, and other working parts with a dry lubricant, such as powdered graphite or a drying spray lubricant such as Boesheild T-9 or LPS 1. Some woodworkers prefer to use paste wax for this purpose, although it takes more time and trouble to apply the wax to gears and hard-to-reach surfaces. Incidentally, drying lubricants are also great for preventing rust on your saw's other ferrous metal components, including saw tables and extensions, rip fence rails, miter gauge bar, and saw blades.
Checking Gear Wear
With the table saw still tipped or inverted, carefully inspect the blade height adjustment and tilt mechanisms for damage or excessive wear. If you can turn the saw's height or bevel adjustment wheel more than 1/8 turn without the blade arbor actually moving, there's too much play in the gears. A good way to check the bevel setting mechanism is to tilt the blade slightly off 90 degrees, lock the wheel, then remove the blade. Grab the arbor and see if you can make the trunnions move. If it moves easily or excessively, many saws have eccentric bushings or repositionable wheel-bearing retainers that allow you to tighten the fit between the mechanism's rack and pinion gears. As the procedure varies with different table saw types and models, it's best to consult your particular saw's manual for specific instructions on making these adjustments.
Pulley Alignment
To transmit power from the motor to the blade arbor with the least vibration, a table saw's belt pulleys (aka sheaves) need to be in good shape and proper alignment. On cabinet saws and portable table saws, it's usually easier to check and align pulleys with the saw still tipped or inverted; on contractor's saws it's necessary to do this with the saw set back upright (but still unplugged).
Inspect the pulleys and replace any that are bent, warped or excessively worn in any way. To check pulley alignment, lay a straightedge across the face of the motor pulley and arbor pulley. On some saws, you may need to tilt the blade so that the straightedge will clear the saw's cabinet or base. The straightedge should make full contact with both edges of the two pulleys. If there's an even gap at one pulley or the other, loosen the setscrew on the motor pulley and move it in or out on the shaft as necessary. To keep the setscrew from vibrating loose, apply a dab of LocTite thread compound to the screw's threads before retightening it. If the gap between pulley surfaces is uneven, loosen the bolts that secure the motor on its mount and shift the motor as necessary to bring the pulleys into alignment.
Belt Wear and Tension
A worn, partially broken or poorly tensioned belt can not only cause noise and vibration, but also reduces the power transmitted from the motor to the blade. With the still saw unplugged, inspect the belt carefully by turning the pulleys by hand. If there are any cracks, ply separations or lumps or areas of uneven or excessive wear, replace the belt right away. If your saw is fitted with multiple belts, you should replace them all at the same time, even if only one is damaged or worn out. Always use replacements that match the original belt(s) size and type. If you need to adjust the tension of the new belt(s) to keep them from flopping or putting excess stress on the motor and arbor bearings, follow the tensioning steps described in your table saw's instruction manual.
Adjusting the Blade Angle Stops
With your table saw clean and back on its feet (but not plugged in), you're ready to adjust the two stops used to set the saw's blade tilt for square (90 deg.) and 45 degree bevel cuts. After removing the saw's throat plate, mount your best saw blade; one with a clean, flat plate. Raise the blade to its full height and crank the tilt wheel until you've solidly engaged the 90 degree stop - just don't crank so hard as to put undue pressure on the stop. Using a large, accurate square, check the blade's squareness to the table from both sides. Make sure the blade's teeth don't get in the way of the square. If the blade isn't square to the table, loosen the 90 deg. stop screw (consult your manual if necessary). Now readjust the tilt angle until the blade is dead square, and reset the stop screw. Repeat the process until the stop reliably squares the blade to the table. Check the accuracy of the final setting by crosscutting a wood scrap in two using the miter gauge.
Lay the parts on the saw table cut end to cut end and flip one part over and see if the ends meet squarely. Readjust the stop as necessary and recheck it.
Adjust the saw's 45 degree stop the same way as described, but use a miter square or a protractor to confirm the correct tilt angle. Check the final miter setting by cutting a scrap stick in half and arranging the 45 deg. cut ends like the corner of a picture frame. Use a large, accurate square to confirm that the beveled parts form a perfect 90 degree corner.
Adjustments for the Miter Slots and Gauge
To keep your miter gauge crosscutting accurately, there are several checks and adjustments you'll need to make. The first step is to make sure that the bar on your miter gauge fits snugly, yet slides smoothly in the table slot. Some miter bars have special inserts that can be adjusted in or out with a small Allen wrench. If your gauge lacks this feature, you can replace the bar with an aftermarket steel bar that has adjustable spring plungers that keep the bar tight in the slot.
Next, check that the slots on your table saw are actually parallel to the blade. If they're not, you'll never get accurate miter cuts, no matter how perfectly the gauge itself is adjusted. Start by mounting a good, flat saw blade and raising it to full height. There are several ways to check the slot/blade parallelism. The easiest method is to use a dedicated tool, such as Rockler's Superbar (available through
Rockler's website) or the Woodpeckers Saw Gauge. These specialized tools accurately fit into the saw's miter slot and use a dial indicator to take readings on the front and rear surfaces of the blade body. If the dial shows a different reading front to back, then the slot is likely not parallel to the blade.
A lower-tech way of checking parallel is to clamp a scrap wood stick to a miter gauge set for a square cut. Extend the stick so that it just touches the front edge of the saw blade. Slide the gauge until the stick is touching the back edge and see if there's a gap (if there's resistance sliding the gauge, reset the stick to touch at the back of the blade and slide it forward). Measure any resulting gap between the blade and stick with an automotive feeler gauge. To make sure that any gaps aren't due to an un-flat saw blade, rotate the blade 90-180 degrees and repeat the process (also be sure and do this if you're using a special saw gauge).
If the parallelism test reveals a discrepancy of more than, say, .003-.005 in., then you should realign the blade and miter slot. On contractors' and some portable table saws, resetting parallel is done by shifting the saw's rear trunnion side to side on the underside of the saw table.
On most cabinet style saws, this job is accomplished by rotating the entire table top relative to the saw's base. In either case, loosen the necessary bolts and shift the position of the trunnions or top slightly, then retighten the bolts and recheck the parallelism of the slots and blade.
Finally, check the angle stops on the miter gauge head by taking cuts and 90 and 45 degrees, and comparing the cut ends as you did when adjusting the blade tilt angle stops, described above. Readjust the screws on these stops as necessary so that they yield accurate cuts.
Adjust the Rip Fence
One of the most important things to do to maintain the cutting safety and accuracy of your table saw is to make sure the rip fence is basically parallel to the blade. A fence set with its back end closer to the blade than the front end tends to pinch the workpiece against the saw blade, which can result in a dangerous kickback.
An easy way to check for parallel is to press two 3/4-in. thick blocks at either end of the saw's right-hand miter slot, then lock the fence down just shy of the blocks and measure the gaps. Ideally, the gap at the back edge of the blade should be just a skosh (.001 - .002 in.) greater than the front gap (this provides just a slight bit of clearance at the back of the cut). Use a feeler gauge to check the gap. If the setting isn't right, loosen the screws or bolts that secure your rip fences bar to the fitting on the front rail and reposition the bar as necessary. Retighten the bolts and recheck fence alignment.
If your table saw has a cursor and scale on the front rail, position the fence bar so that its face lightly touches the saw blade teeth and lock it down. Reset the fence's cursor to read zero on the rail's scale.
Set the Throat Plate Height
The throat plate that fills the gap between your saw table and the blade must be set level relative to the surrounding saw table and so that it doesn't rock as the workpieces passes over it. This prevents workpieces from hanging up or tipping as they pass over the plate, which can result in miscut parts or worse.
Most stock and aftermarket table saw throat plates have small screws that allow you to set the plate's height and flatness. With a straightedge or the butt of a large try square bridging the table over the throat plate, adjust the screws until the plate is flush with the straightedge/try square and doesn't rock. You may wish to set the plate just a hair lower at the front, to eliminate any chance that the stock will hang up on it. If your plate doesn't have screws, use masking tape to shim the underside of the plate to raise and level it.
Extension Tables and Saw Level
If your table saw has bolt-on extension tables, check them with a straightedge or other flat block, to confirm that they're still aligned to the main saw table. Loosen the bolts and tap the extensions with a dead-blow mallet to realign them as necessary.
It's also a good idea to level your table saw table. Check by placing a carpenter's level on the top, both parallel and perpendicular to the blade. Readjust level by raising or lowering the feet on the saw's base, or driving shims under the saw cabinet.
Check the Blade Guard and Splitter
An important part of keeping your table saw safe to operate is making sure that the blade guard is in good shape and operating properly. Inspect the guard to make sure that its mounts and pivots are in good shape. The guard should float up over the top of workpieces easily; if it doesn't, lubricate the pivots. If the guard itself is cracked, broken or otherwise malfunctioning, it likely best to simply replace it.
If your guard has a splitter, use a straightedge to make sure that it's both parallel to and in line with the saw blade. If it's misaligned, loosen the splitter/guard mounting bolts or screws and move it sideways as necessary. Also inspect the guard's anti-kickback pawls (if your guard has them) and make sure their tips are sharp and springs are in good working order. If not, resharpen the tips with a file, and replace pawl springs if necessary.
Regular Blades and Table Maintenance
An easy thing to do regularly that helps improve table saw performance is to clean your saw's table top and blades so that they're shiny and rust free. Corrosion forming on saw table surfaces is a very common problem. But unless your shop is in a swamp, rust or corrosion (that forms on alloy tables) is relatively easy to deal with. First, remove crud and corrosion using a cleanser designed for either ferrous or non-ferrous metals, depending on whether your saw table is cast iron or aluminum alloy. Apply the cleanser and scrub the surface with a plastic abrasive pad, such as ScotchBrite®, and allow the surface to dry thoroughly (use a hairdryer, heat gun or compressed air to speed things up). To keep corrosion from coming back quickly, apply a dry coating, such as BoeSheild T-9, or Bullfrog rust preventative.
Clean all your saw blades, dado sets, molding cutters, etc. often to remove pitch and resin that builds up on the teeth and plate surfaces. One way to remove grime is to scrub your blades using a nylon-bristled brush and a specialized blade/bit cleaner, such as "Oxi Solve" or "Pitch Rx." Another approach is to spray blades with a household oven cleaner.
Working outdoors or in a well-ventilated space, lay the blade on newspaper or cardboard that you can throw away afterwards. Wearing gloves and a mask if you're sensitive to cleanser fumes, spray the blades' surfaces and coat them thoroughly. Leave the cleaner on for at least 1/2 hour before rinsing the blade with lukewarm water. Dry it immediately with compressed air or a hairdryer, then coat the blade with a drying lubricant.