A few weeks ago my house was burgled, and the thief stole most of my construction tools. I was devastated. However, my friends came together and created a fund that has enabled me not only to replace the stuff that was stolen — I’ve also been able to add a big new tool. Wow, my friends are great!

The tool I added is a SawStop Jobsite Table Saw. I got it for a lot of reasons; here are the top two. First, I want a table saw big enough to cut big plywood but small enough to store in the garage. This one is pretty easy to move around on its integrated hand truck.

Second, I wanted a saw with tech that recognizes a finger and refuses to cut it off. I’m very, very impressed by the testimonials from YouTubers I admire (like this one and this one) about how the SawStop actually stopped and they walked away from a situation where they could have been very seriously injured.

A table saw blade turns about 4000 rpm, the teeth are moving at about 200 feet per second, around 1365 mph. The teeth point toward the user (into the board you’re cutting), so the teeth can (and sometimes do) catch a finger and pull it into the blade. It happens so fast that you can be seriously injured multiple milliseconds before a signal can make its way to your brain. I decided to do the math.

A signal from hand to brain takes about 20-40 milliseconds (that’s just the transmission time, not considering any thought from the brain, let alone a reaction and retransmission). In half the shortest possible transmission time, 10ms, the teeth on the blade move about 2 feet. There are 50 teeth on my blade, so in 10ms, about 30 teeth pass through a given point. When I hit my hand slowly on just one tooth (like when I’m installing a blade), I get a good nick. 30 teeth (driven with effectively infinite power) could easily sever a finger in half the time it would take for the signal to reach my brain.

This model has a capacitive touch sensor in the blade. When it touches something conductive, like, say, a finger, it stops in <0.0004 seconds, which is less than the travel time for one blade tooth. The videos and testimonials are amazing. I love the one where they push a piece of steak into the blade and it stops with only a tiny nick. I bought this model bc I think it will reduce the chance of losing something important when I’m distracted for an instant.

However, I’m a little sad I can’t also have a hyper-precise Byrnes Mini Saw. It looks absolutely gorgeous. However, they’re not being made right now, and it would really be too small for anything other than building small enclosures for my electronics. But then again, most of what I want to do is build small enclosures. You can see the dilemma.

Availability won out, and I got the SawStop. Right away I noticed that making cuts with the fence isn’t precisely square. The key test is to cut a board on each side in turn, and then check square on the final cut. A simple cut using the saw’s fence is not all that close: look at all the light under the rule.

I decided to build a cross-cut sled, which seemed to me perhaps the most fundamental helper tool for a table saw. I followed the basic pattern described by Tamar at 3×3 Custom, though mine is somewhat simpler. There are tons of videos online about how to do this, so I’ll hit the highlights:

  • cut plywood for the back and front fence; I used two sheets of 1/2" glued together. I clamped them to a monster 1/4" thick chunk of aluminum L frame I have from an old project to make sure that as the glue dried, the fences stay as flat as possible. After they dried, I trimmed them so they are flush.
  • I cut runners out of a maple board; I used the sneak-up-on-the-cut method that Newbie Dan describes. I don’t know whether I cut the strips properly to account for how they shift with the weather. I used a Grr-Ripper to control the wood as I cut it. (btw I like the Grr-Ripper a lot).

The image below is the bottom of the sled after I secured the back fence with a zillion screws.

The sled itself is about 18" deep by 24" wide, with a big chunk cut off the back left where I don’t think I need too much support and I can reduce weight (this idea comes from Tamar).

By far the most important part of the sled is getting the back fence perpendicular to the blade. There’s an amazing trick for this, invented by William Ng, called the "five-cut" method. The idea is to cut a board on each side in turn. The error (i.e., the amount the cut differs from perpendicular to the blade) compounds with each cut because the cut side becomes the base of the next cut. The amplification of the error makes it easier to measure and to correct.

I’ll leave the explanation of the method to others – there are tons of great explanations of how to do the cuts and the calculations. Here’s my final cut with the associated measurements.

(note: the A measurement is 1.1700, and B is 1.1575; when. I wrote on the board, I omitted the ‘1’ in the tenths position, oops). From this, you can calculate that my sled’s error is ((A-B)/4)/len(test) = 0.00033 per inch. That is, cuts made with this sled will be off square about 3 ten-thousands of an inch over every inch of cut.

So if I cut a board 24" square, the diagonal in one direction would be around 0.02" different from the diagonal in the other direction. I can definitely live with that! Of course this sled is too small to cut 24" square, but you get the point.

This is a first attempt. The runners aren’t great, the fences should be 3/4" rather than 1/2", and the whole thing should be made of higher-quality plywood. But it’s a great "hello, world" with my new saw.

And it’s a great lesson that in woodworking (probably in other areas, too), the great tool only gets you part of the way. There’s some skill, sure, but also some technique (which isn’t quite the same as skill).

Finally, I’m really glad to have a way to cut seriously square. This is a great first post-burglary project. I’m deeply grateful to my friends.

PS: yes, we changed & upgraded all the locks, and we added cameras that save video to an online repository (the "cloud"), but crucially for me, the cameras do not connect to the police. And in the garage, the saw is chained to a bolt drilled & epoxied into the foundation. Of course we could be burgled again, but it’s going to be tougher for the next thief.