table saw, locking mechanism

Table Saw Fence

Through the years I’ve worked with a number of table saws, from my dad’s venerable Craftsman to a Delta Unisaw to the portable tablesaw I used when I was in construction. The one thing I learned through all this, is that the fence is the most important part of any table saw.

Now, I know that there are people who will disagree with me, and I’m not talking about safety measures such as using the push stick. Most of them will say that the blade and the blade drive are the most important part. But, while I agree that they are important, I don’t think they are more important than the fence. If there’s a little bit of wobble in the blade, due to a poorly designed or aligned drive, it will mar the finish of the cut. But if the fence is off, the cut will be crooked. That’s a bigger problem to deal with.

But not all fences are created equal. Far from it. If there’s one thing I’ve seen through all the table saws I’ve used, it’s that there are a lot of poorly made table saw fences out there. If you’ve got a saw with one of the bad ones, it’s going to affect every cut you make.

There are two things you can do, besides just putting up with it. The first is to buy another table saw; and the second is to build yourself another fence. While there are some fairly complex fence designs out there, you can actually make one fairly easily, which will provide you with excellent service. But first, there are a few key things that you need to keep in mind, when designing and building any table saw fence:

  • Perpendicularity – The key thing that any fence has to be able to do is maintain perpendicularity with the saw’s table. Another way of looking at this is that it has to remain parallel to the saw blade. Poorly designed table saw fences don’t have enough of a crossbar for the “T” portion of the fence, causing it to have a tendency to wobble.
  • Rigidity – Any table saw fence is only going to work if it can maintain rigidity. It can’t flex under the pressure of material being wedged between it and the saw blade, especially if the cut starts to go crooked.
  • Security – When you clamp the fence in place, it has to stay there, no matter what. Just as with rigidity, there are times when the material between the fence and the sawblade will push against the side of the fence, trying to move it. That can’t be allowed to happen.
  • Ease of Use – Any fence which is hard to move and clamp in place is not going to be used. This is why commercially manufactured fences have an over-the-center clamp. That’s fine, if you’re making it out of metal, but a wood over-the-center clamp is only going to last so long. Therefore, I’ve chosen another design.

For this design, I’m using a combination of wood and aluminum extrusions. The fence itself, the part that guides the wood, is made of wood, but the “T” head and the rail are made of aluminum. That allows me to take advantage of the strengths of the two materials, applying them where they will do best.

Making the Fence Rail

For the fence rail, I’ve chosen a 12 gauge piece of 1-1/2” square “C” channel. This is the same sort of channel that you might see used for the rail on a horizontal sliding door in a factory or a gate. Normally, these are made of steel, rather than aluminum, but I’ve gone with aluminum for weight. If you can’t find this material in aluminum, you can just as easily make it out of roll-formed steel.

Typically, a fence rail is the width of the table, but I’ve extended it six inches beyond the edges of the table on both sides. This ensures that my fence will still maintain perpendicularity, even when at the extreme edges of the table. If you were planning on building extensions onto your table saw table, I’d do that, before building the fence, or make your fence long enough to accommodate those, while still extending past the edges of the table.

The saw’s table should already have holes drilled and tapped into the front edge, from the original fence rail. You should be able to use these same holes, if you remove the existing fence rail. If there are not enough, you may need to drill some additional holes. As the table top is probably made of cast aluminum, this should not be a problem.

Be sure to mount the guide rail so that it is slightly below the surface of the table, to ensure that it will not hold the fence off the surface of the table. Also ensure that it is perfectly level or parallel to the surface of the table, so that the fence doesn’t ride up and down, vertically, as it moves across the table.

Building the Fence

I’ve chosen to use MDF (medium-density fiberboard) for the fence itself. Another good option would be applewood plywood if you can find it. The thin plies of the applewood are perfect for this sort of project, and it is extremely stable. That stability is why I chose MDF, which is easier for me to get.

The fence itself is made of four, ¾” thick strips of MDF, all 3” wide. Because I am working with a fence that is not all that reliable (the one I’m trying to replace), rather than count on the fence’s clamping system for perpendicularity and security, I clamped the existing fence in place with two C clamps, one at each end, after checking the distance and the perpendicularity with a square.

table saw fence, sketch, mdf fence
Building the table saw fence

In the diagram above, you can see how the four strips of MDF are connected together, to form the fence. These were glued together and nailed, with brads and then screwed for extra strength. To ensure that the screw heads would not protrude from the surface of the fence, the pieces were drilled (clearance holes only) and countersunk before assembly. Once glued and nailed. The pilot holes for the screws could then be drilled and the screws driven home.

I chose to make both sides of the fence equal, so that it could be used either right-handed or left-handed, although I do most of my cutting with the fence to the right of the blade. I could have also done basically the same thing, using a 2” x 4” aluminum C channel, rather than the two middle strips of MDF, but this would have required buying one more type of aluminum extrusion, adding to the project cost.

I also chose to make the fence overly-long, just as I made the rail overly wide. My table saw has a support extension behind the table, so I made the fence long enough to reach this support, even at its longest extension. This increases the surface I have available for the workpiece to ride against, helping to ensure that I run it through the saw straight and evenly.

The aluminum angle, shown in the drawing above, forms the “T” head of the fence and is bolted to the bottom of the fence. I would recommend using three to four bolts, for security, along with nylon insert locknuts. After all, this is the most critical part of the assembly, as it needs to be exactly perpendicular to the fence.

To check perpendicularity, use the fence, with the T head attached, as a square to mark a line on a piece of sheetrock or plywood. Then flip the fence around, putting it on the other way. If it is exactly square, when you mark the line from the other side, it should exactly overlap your original line.

Making the Locking Mechanism

In order to make the fence easier to build, I’m using a knob and screw as a lock, rather than an over-the-center lever mechanism. Not only are those harder to build, they must be extremely precise to work properly. A screw and knob on the other hand is something easily accomplished in a home workshop.

Before we look at the locking mechanism itself, we need to talk about the “T” head for the fence. Opinions differ, but most good fences have a head that is about 1/3 the length of the fence. I would modify this by saying that your head should be at least eight inches long. However, unless you have a huge saw table, any longer than a foot will be difficult to work with. Be sure to radius or chamfer the corners of the aluminum angle you use for the “T,” so that you don’t injure yourself when you run into it.

The locking bar, which goes inside the fence rail, should be roughly the same length as the fence “T.” You can make it out of whatever material you have available, but it should be at least ¼” thick and able to support being threaded, without the threads pulling out. This pretty much limits us to aluminum or steel.

table saw, locking mechanism
Table saw locking mechanism

As you can see in the diagram above, the locking mechanism consists of nothing more than a bolt with a knob attached, running through the T head and into the fence rail. On the inside, the bolt goes through the locking bar. To lock the fence in place, all that is needed is to tighten the knob, once the fence is positioned.

You need to be sure that you use a good knob or knob/screw combination; one that won’t come apart as torque is applied to it. I would also go for the largest thread size that you can reasonably fit through the opening in your frame rail. If you can get it, use fine threads, as that will be easier to work with. You can buy these through industrial supply companies, rather than trying to buy one at your local hardware store or home improvement center.

You will need to drill and tap the locking bar to match the thread of your knob/screw. If necessary, cut the knob/screw to length, and grind a chamfer at the end of the bolt. You want it to go all the way through the locking bar, but you don’t want it to be able to hit the bolts that are holding the fence rail to the table saw table.

One last item that is needs is a spacer for the knob head to press up against, when it is tightened. This must be made of some sort of metal, as the tightening of the knob will try to compress it. If you use plastic, for example, it will crush and your fence won’t be secure. Placing a washer between the knob head and this spacer, to act as a thrust washer, will help it to tighten and loosen a bit smoother.

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