SIGHTING IN YOUR TABLE SAW

Those who are hunters know that before hunting season comes you have to take your rifle out and make sure that the bullet goes where you sights say it is going to go. Your table saw is the same. It needs to be sighted in when you first get it, either new or used and on a regular basis after that. A properly tuned saw will give predictable cuts, both rip and crosscut.

The equipment that is required to do an exact job is not expensive. You can make a simple alignment tool from some hardwood scraps and a $9.00 dial indicator. This will give results that are within half a thousandths or less, much more accurate than is needed. The dial indicators that I use come from MSC supply. If you are going to order one or two, also get a dial caliper at the same time. The part numbers are 76450071 for the dial indicator and 76367069 for the dial caliper. They are on sale almost all the time. The web site is www.mscdirect.com.

The table saw alignment tool is shown in figure 1. Is consists of two pieces of hard wood ½” X ¾”. The holder for the indicator is about 8” long and the crosspiece is about 5” long. The holes in the holder are spaced ¾” apart. They are held together with a ¼” carriage bolt that is countersunk into the bottom of the crosspiece. See figure 2.

      Fig.1                                                                                             Fig.2

To get straight and accurate cuts on the table saw, the blade, the miter slot and the fence need to be parallel. You will notice that I said miter slot and not slots. It is quite possible that the two miter slots will not be perfectly parallel to each other. For that reason I do my alignment procedures using the left slot because that is the one that is used most of the time.

On a cabinet type saw, the trunnions are attached to the cabinet and moving the table makes adjustments. On a contractor type saw the trunnions are attached to the table and moving the trunnions makes adjustments.

BEFORE STARTING THIS PROCEDURE, UNPLUG THE SAW

One of the first things to check is the trueness of the arbor. Putting the indicator point near to the center of the blade and rotating it by hand using the arbor nut can do this. This should be within the .003” to .005” range or less. If it is not, you will have a significant wobble in the blade. If the arbor is good, you can then check the flatness of the blade by placing the indicator point near the edge of the blade inside the line of gullets and again rotating by hand. A good blade will have very little wobble.  See figures 3 and 4

      Fig. 3                                                                                           Fig. 4 

To get the saw blade parallel to the miter slot, start by raising the blade to the maximum height and marking a tooth with a marker. I use the marked tooth to make the measurement at the front of the saw and then rotate the blade to bring that tooth to the back. This eliminates any errors caused by wobble in the blade. See Figures 5 and 6.

      Fig. 5                                                                                           Fig. 6

The alignment tool should be loose in the slot. Hold it against the right side of the slot when measuring. This should be the same side that you hold sled and jigs against when cutting. If corrections are to be made, loosen the trunnion or table bolts as appropriate and nudge with a block of wood and hammer. It may take several tries to get the desired result. When you have the two measurements the same or as close as you wish, retighten the bolts and then recheck the measurements again. If they have changed, repeat the above steps until you are satisfied.

To align the fence, lower the blade and bring the fence over to where it will contact the alignment tool in the left miter slot at the front of the table. Clamp the fence in place and note the reading on the indicator while holding the indicator against the right side of the slot. Move the indicator to the rear of the table along the slot, holding it against the right side as you slide along. Take note of movement of the indicator dial and the reading at the rear of the table. Movement as you slide along the slot, indicates waves in the fence surface. I like to have the fence perfectly parallel to the blade, but others like to have the fence tapered up to .005” to the right, front to rear. If you do go with the taper, remember that you can not use the fence on the left side of the blade without correcting for this. See figures 7 and 8.

      Fig. 7                                                                                           Fig.8 

The last thing to check is the alignment of the tape measure and indicator that allows cuts to be measured with the fence. Take a board and rip it at a given measurement on the fence indicator. See fig. 9. Then measure it with a dial caliper and make any necessary corrections to the indicator on the fence. See fig. 10. Repeat the test until you can get within .005”.

      Fig. 9                                                                                           Fig. 10

I use a home made splitter to keep rip cuts from binding on the blade and it reduces the tendency to kick back and also eliminates burning of the wood that happens with some woods, especially fruit woods. The splitter is .005” thicker than the blade kerf, .130” for a 1/8” blade. See figure 11. It is centered on the blade. This puts a slight pressure on the board towards the fence as it goes by the blade and prevents the blade from contacting at the rear of the cut. See figure 12.

      Fig. 11                                                                                         Fig. 12

This whole procedure takes little time and will give you a saw that makes accurate and repeatable cuts, quickly and easily. You will find that you can rip more accurately using the fence indicator and tape measure, than you can, measuring from a blade tooth to the fence and in less time. I do check the distance with a rule to verify the distance as in “measure twice and cut once”.