Workshop Project: Table Saw Tune-up
As durable as most table saws are, they do require attention from time to time. If you're table saw is is leaving rough saw marks, burning wood or bogging down when you rip average stock thicknesses, chances are something's amiss, and it's time to diagnose the problem.
Fortunately, in most cases that problem can be easily fixed with a table saw "tune up" or a modest investment in a new, or more appropriate blade. In this article, we'll take a look at the most common table saw problems, offer some advice on getting your saw back on track, and point out a few resources for more in-depth table saw research.
Are You Using the Right Blade?
Using a dull, inappropriate, or inferior saw blade is the most common source of poor quality cuts, burns and slow, difficult feed. A dull saw blade won't cut well, of course, and should be sharpened. But you should also evaluate the quality of the blade, and check to see whether it's the right kind for that type of cuts you want to make.
Do these things first: Even if you're saw has other problems, you won't be able to accurately diagnose and correct them if you're using a dull or poor quality blade, or a blade that wasn't designed for what you're asking of it. If you're a little fuzzy on how to judge saw blade quality and on what the different types of blades are designed to do, see our Woodworking Tips article on selecting the right saw blade. It will help you get up to speed on the most important saw blade facts and terminology.
Aligning the Blade With the Fence and Miter Slot
For your saw to cut cleanly and safely, it is extremely important for everything used to guide stock past the blade to be parallel with the blade. In other words, you need to make sure that both the miter gauge slot and the saw's rip fence are in as near perfect alignment with the blade as possible. here is an alignment procedure that can be performed with tools that you are likely to have on hand:
Most fences have a provision for adjusting parallel alignment – again, the manufacturer is the best source of information on the procedure. If the fence cannot be accurately adjusted, or if the degree of disagreement between alignment measurements varies as the fence is positioned and repositioned, there is a strong possibility that your current fence is incapable of providing reliable parallel alignment. If you are generally satisfied with your saw's other qualities, correcting the problems with the fence is worth considering.
- Unplug the saw and raise raise the blade to its highest position.
- Lay a straight edge on the surface of the table so that it is centered across the diameter of the blade and tight up against the blade plate (make sure that the straightedge is in contact with the blade plate itself, and not resting on the blade's carbide teeth).
- Next, measure the distance from the straightedge to the miter slot milled in the surface of the table at each end of the straightedge. If the measurements do not agree, the blade is out of alignment.
- Follow the manufacturer's instructions for adjusting the blade alignment. In most cases this will involve loosing three of the four bolts that attach the trunnions to the saw, tapping the assembly into the correct position and re-tightening the bolts (be sure to check the alignment again when you are finished to make sure that the act of tightening the bolts didn't pull the blade out of alignment).
- Now you are ready to check the alignment of the fence. Use the straightedge, again, to check the alignment of the surface of the fence and the surface of the blade. The measurements of the distance from the surface of the fence at the front end of the fence and the back end of the fence to the straightedge should agree. If they don't, the fence is out of alignment and should be adjusted.
Checking for Arbor Runout
Ideally, a table saw blade should spin in a perfect circle, without deviation upward and downward or from side to side. In reality, there is always a certain amount of inaccuracy in the path of a blade, and the term used to describe it is "runout." Checking table saw runout down to thousandths of a degree isn't hard to do, but it does require a more sophisticated measuring device than you may have on hand - a dial indicator - and some special rigging. The whole alignment package is available in specialized table saw alignment tools, such as the Master Plate with Super Bar.
How do you check table saw runout? Here's the basic procedure, as described by Michael Dresdner in Woodworker's Journal eZine:
"Unplug the saw and raise the arbor to its highest position. Mount a flat plate (I use a blade stabilizer) onto the arbor and snug it down with the retention nut. Mount a dial indicator on a magnet and set it on the table with the tip reading the face of the plate near the outer edge. Spin the arbor by hand and watch the dial. As you go through a rotation, watch how much the dial changes from the highest to lowest reading. That is the amount of runout. If luck is with you, it should be less than .005" on a 10" plate, and half that on a 5" plate."
The best way to test bearings is to listen to them while the saw is running. You can hear a bad bearing before spotting it any other way. Good ones are quiet; bad ones make all sorts of wierd noises.
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