What is a Table Saw Sacrificial Fence, And How You Build One

The table saw sacrificial fence is a special shop-made fence that literally sacrifices itself to serve its purpose.

You can use the sacrificial table saw fence to help you line up notches that run along the edge of a board. This type of cut is called a rabbet, and to get a better idea of what a rabbet is, vs a dado or groove, read this article here on woodworking grooves.

A good sac fence (short for sacrificial fence) is usually custom built to fit right over you main rip fence. But in a pinch, you could also just clamp a board to the side of your main rip fence. This works as long as you can still make the cut safely without the clamps getting in the way.

But as for me, I wanted a dedicated, long-lasting sacrficial fence that supports vertical feather boards, and that’s what I’ll be showing you here.

I built my table saw sacrificial fence so that it’s really easy to line up, and it locks in place with a simple plastic knob which applies pressure on one side to keep the fence from sliding.

You can build a sacrificial fence with basic plywood, by creating a partial box around your main rip fence.

Here’s a few shots of my sacrificial fence set up on my table saw:

You’ll get the most benefit from this fence when you pair it with a set of stacked dado blades. 

I prefer a tall fence design because when you are making any kind of groove or notch cut, where the blade does not go all the way through the board, you’ll get better results by using a feather board.

You can clamp your feather board right to the sacrificial fence if it’s tall enough. Here’s a shot of my setup with the feather board clamped to the fence.

This keeps even consistent pressure downward on the board, and is important so you’re rabbet depth is even all the way through.

Without the feather board, you’ll sometimes find that the work piece tends to raise up just a bit while making the cut. This affects the depth of the rabbet and you may not even know it happened until you go to glue it up to it’s mating piece. The other piece will not sit flat in the rabbet.

Related: Build Your Own DIY Feather Board

How To Build A Sacrificial Fence

To build your sacrificial fence, basically you’ll want to box in your main fence. I found it easiest to use pocket hole joinery for this process.

You’ll use 3 pieces to build the main sac fence, with the tall piece against the blade-side of the rip fence. These pieces should be about the same length as your main fence.

Have a look at my clamping setup. It’s a strip of pine wood about 1/8″ thick. About half of it is glued to the inside of the fence. The other half flexes in and out.

Underneath the flex side, I drilled a hole and mounted a t-nut, which I counter-bored for clearance. Then my 1/4″-20 bolt goes through and pushes the shim into the side of the fence.

The top horizontal piece of the fence is just barely over 1/8″ wider than the fence, to give clearance for this shim.

Now attach the 3 pieces with pocket joinery and add some small support pieces to help keep the fence ridgid and square.

Drill a ½” hole in the top near the end and glue a piece of dowel in so it will act as a stop. You’ll use this to line up your fence so it’s the same every time.

Just attach the fence and pull it back until the dowel is against the end of your rip fence.

If you’re wondering why my fence has all the odd angles, it’s to help reduce weight where possible. This whole fence is made from ¾” plywood after all.

How A Table Saw Sacrificial Fence Works

To use your sacrificial fence, you’ll first attach your dado set to your saw. You’ll want the stack of blades to be wider than what the rabbet will be, since part of the blade set will be underneath the fence.

If it’s the first time you’re using the fence, then go ahead and lower the blade until it’s completely underneath the throat plate of your table saw.

Now attach your sacrificial fence to your rip fence, and slide it over the blade. The sacrificial fence will be over the blade, but you don’t want your rip fence itself over the blade. 

With the sac fence locked in place and your main fence locked down, start the table saw. Now slowly raise the blade so it goes into the sac fence only. Raise it up about an inch into the wood, this will be more than enough height  to cut rabbets with your fence.

Now you can shut off the saw and lower the blade where you need it. Slide your fence away and set the height of the blade first.

Now slide your fence over and measure the blade set from the left edge of the left blade, to the fence. This will be the width of the rabbet.

Once it’s locked down, you can set up your feather board to help keep steady, consistent downward pressure on the work piece.

Now run a few practice cuts to get the width and depth of the rabbet just right. Make adjustments to the fence position and the blade height until you get it where you want it.

Taking a little extra time during this process is worth it when you can ultimately cut all your rabbets with this single setup of your table saw.

Now with everything where you want it you’ll be able to cut duplicate rabbets on multiple pieces for your project. The depth and width will be just right on each one.

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Related:
Woodworking Rabbets Explained
Pocket Hole Joinery
How To Build Base Cabinets
9 Useful Shop Projects For Woodworking and Tool Upgrades