Table saw technique, cross-cut dados on multiple boards

Question

I bought a table saw recently and it's the most terrifying tool I own.

I want to cut a 5/8" dado across four 5" wide boards in identical positions, about 14" from the reference edge. I have a 1/2" stack so I'll have to make two passes. What is the safest technique for this?

It doesn't feel good to use the fence, one at a time, because it's difficult to keep the board flush to it given only 5" contacts the fence with 14" distance to the blade.

I could use the mitre slide but I'm not sure how to get consistent position for multiple cuts. Is there some magic jig I can cut or a good marking / measuring technique for the mitre slide? (I am thinking, maybe I can make an "L", laying on its side, with the long edge mounted to the slide and the short edge 14" from the blade, but I foresee problems keeping the angles true and the short edge sturdy; I could make it out of scrap steel maybe but now it seems like a whole project of its own.)

Can I somehow load all the boards at once? I was thinking maybe I could temporarily mount them all to a piece of plywood or something then run the whole thing along the fence, maybe once to make all the edges flush then flip it around to cut the dados. But I don't want to put screw or brad holes in the boards and I'm not sure how to mount them otherwise.

How can I safely and accurately make these cuts?

Answer 1

I bought a table saw recently and it's the most terrifying tool I own.

As a beginner, that is the right attitude. I note that the most dangerous time will be when you are no longer a beginner but not yet an expert; that's when people make careless mistakes. I try to remind myself frequently that my table saw is trying to kill me.

It doesn't feel good to use the fence, one at a time, because it's difficult to keep the board flush to it given only 5" contacts the fence with 14" distance to the blade.

Correct. This is a recipe for the work rotating and kicking back.

And you never want to use the miter slide and fence in combination because again, the work can bind against the fence and rotate away from the miter. However there is a way to safely use the fence as a reference; more on that in a minute.

I could use the mitre slide but I'm not sure how to get consistent position for multiple cuts. Is there some magic jig I can cut or a good marking / measuring technique for the mitre slide? (I am thinking, maybe I can make an "L", laying on its side, with the long edge mounted to the slide and the short edge 14" from the blade, but I foresee problems keeping the angles true and the short edge sturdy; I could make it out of scrap steel maybe but now it seems like a whole project of its own.)

If you're going to go to that kind of trouble then it is better as others have noted to simply make a sled. I use my sled for all but the most trivial cross cuts.

Can I somehow load all the boards at once? I was thinking maybe I could temporarily mount them all to a piece of plywood or something then run the whole thing along the fence, maybe once to make all the edges flush then flip it around to cut the dados. But I don't want to put screw or brad holes in the boards and I'm not sure how to mount them otherwise.

Not worth it. It'll be hard to keep everything together and awkward to try to cut so much at once. And this is not the last time you will have to solve this problem.

How can I safely and accurately make these cuts?

The cheap solution is to use the fence as a reference but not keep the work against the fence while it is being cut. You reference the fence before the work engages the blade like this: (Though I personally would be inclined to use the other miter slot.)

Clamp a scrap known-to-be-flat board to the start of the fence, set the fence-with-board as your reference, and push the work against the board before you start moving the miter. When the work engages the blade it is past the board, and so there is no chance that the fence will bind against the work.

But again, building a sled pays big dividends. Repeatable, accurate cuts are easier, and you can build as many safety devices into a sled as you desire. My sled is covered with points where clamps can be added to hold work in place. Hands are terrible clamps.

Answer 2

There are 2 points of accuracy you'll want: keep the piece moving at the same orientation and get the correct distance from the reference edge to the blade. The second is easy, just set the fence tot he correct position and you are set for that.

If you are uncomfortable using the fence as a stop, then you can clamp a bit of wood to the fence so the back end does not reach the front of the saw and use that as the reference surface. By the time the piece is cut it won't be rubbing against the block any more.

For the orientation then you can use the miter slide and the fence in combination: The miter slide will prevent the piece from turning and the fence will be the point of reference.

Make a sled that runs in the T slot next to the blade and put the workpiece on that.

The sled can consist of just a piece of plywood with a wooden runner screwed in the bottom. Perhaps with a few dowels that you can use as a backstop.

Then because it will be the sled doing the sliding and it will be at a fixed angle, the workpiece can be kept at a consistent angle much easier. Again use the fence as a side stop for the 14".

Answer 3

You are correct to not want to use the fence alone for these cuts. That has a high probability of ending very badly.

The miter gauge that came with your saw should be adequate (use it in conjunction with the fence for accuracy), but since it sounds like you're not comfortable with that, here's some alternatives:

Build a miter saw sled. Lots of versions of this on the interwebs, but at a minimum, it's a sheet of something that runs in your saw's tracks that has a perpendicular fence. It can be as simple or as snazzy as you'd like.

With over-long stock, attach them to ply or whatever and run them through as a group. Cut off the ends that have screw holes through them and you'll be left with what you want. The hard part of this plan is attaching them securely enough that they don't twist or rack while on the ply.

It's right to be wary of the tablesaw, but practice will improve that. If it's a huge dado, take it in progressive heights, so you're not cutting everything at once.

Answer 4

I will assume that you do not have a dado stack for this? They are a set of blades designed to cut a dado in one pass. That way using a fence and a mitre sled (most table saws come provided with one.). It does get easier and safer than that though.

Some general safety tips apply

• make sure that if the board is longer than your table saw that it is supported.
• The tips discussed in all the answer here: How do I prevent dangerous kickback on a table saw?
• Keep your hands away from the blade and use push blocks or push sticks if you are not using a sled.
• Any other table saw safety Q&A we have here

Blade Choice

To save yourself from having to clean the dado (at least to minimize it) use a flat tip blade. See more: How do I look for a table saw blade with non-angled teeth?

Jig it up

Crosscut sled

A basic cross cut sled (something every table saw owner should have) would make this process easier. A wonderful, must watch video about making one from come from WNWoodworks; the youtube channel of William Ng. These are discussed here in greater length: What is a crosscut sled used for?

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Still would need to have stops on the sled

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You can just use something as simple as a block as a stop. As long as you measure properly you can make the same cut on multiple board. After each board is cut then adjust the stop and cut all the boards again.

Box Joint

A lot of the tutorials you would see for box joint jigs would work in this area as well. This particular one by Matthias Wandel at WoodGears, while not sized for your project, shows that you can make precise and progressive cuts one pass at a time. These jigs have a more controlled and automated way to control the "stop" mentioned earlier.