How to make a sacrificial rip fence that never wears out
Like a lot of woodworkers, I use a dado set on my tablesaw. And like many of you, I learned (from Norm Abram) that when you cut a rabbet with a dado set, you make a stack that is wider than your rabbet, put a sacrificial fence on you rip fence and raise the blade into the sacrificial fence. Then you adjust the fence so the width of the blades exposed is equal to the width of your rabbet. Without the sacrificial fence, the dado set would cut into your rip fence–not good.
I often use the same trick when cutting tenons with a dado set. I set up the dado blades and sacrificial fence and guide the rail through the blades with a miter gauge. I use the sacrificial fence as a stop, too. (Some might gasp and wonder how I can do that, as you supposedly should never use the miter gauge and rip fence together like that. But, I’m not making a through cut, so there is no danger of an offcut getting traped between the blades and the fence and being thrown back at me. So, it’s safe and I’m comfortable doing it. If you’re not comfortable doing it, don’t.)
What I’ve always hated about the method is that you have to cut into the sacrifical fence. Eventually, it gets ragged out and needs to be replaced. And if you use the blade at a lower height than a previous cut,there will be a gap in front of the blade and behind it where the fence was cut away when the blade was higher. I don’t like that all.
Well, I won’t have that problem any longer. On a recent trip to Michael Fortune’s shop, I watched him set up to cut some tenon cheeks with a dado set on this tablesaw. But he didn’t bury the blades in the sacrificial fence. Instead, he raised the fence until it was just above the teeth. He could still “bury” the blade in the space beneath the fence, but didn’t need to cut into it. And, importantly, the space between the raised fence and the dado set is a place for dust to fall and be out of the way (instead of against the fence, which becomes a mess that you have to clean between every cut so that it doesn’t prevent you from pushing the workpiece against the fence.). Take a look at the photos to see how to do it. I’ll never go back to the other method.
PS: I’ve answered some questions/objections in the comments section below.
Bury the blades without ruining your fence. All you have to do is raise the sacrificial fence just a bit higher than the blades.
Set the fence height. The bottom edge should be just above the blades. That allows you to have the fence over them and so bury them, but it's not so high that you need worry about the workpiece falling into the gap between the blades and fence.
NOTE: This photos shows the relation between the blades, fence and workpiece. I am not actually cutting here and the TS power was disconnected. Do not make cuts with your fingers in this position!
The tenon still rides on the fence. Here's another reason to have the fence just above the blades. After cutting the second cheek, the tenon left behind still has a surface to register against.