Introduction: Table Saw Crosscut Sled - Simple & Precise
Since upgrading to my new table saw a few months ago, I need to start putting together all new sleds and jigs, first up is a good crosscut sled.
I want to thank Acme Tools for their support with this project and video. If any of you are looking at buying or upgrading a table saw, Acme Tools as a really good post on their blog about the top table saws for 2018. My old Dewalt Jobsite saw is on that list, and so is my new SawStop saw. Having personal experience with two of their top 10, I would trust what Acme Tools has to say on the matter because I have loved both of my table saws. Weather you are looking at an entry level tool or a high-performance machine, they have compiled the information you need to make a good decision. Click here to check out that write up for yourselves.
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Step 1: Runner Options
There are really only two hyper-critical parts of a crosscut sled - the runners and the back fence. Other than that, the rest is all just personal preferences and some bells and whistles.
It is critical to have very stable runners that fit without any slop inside the miter tracks in the saw. There are lots of different materials that will work for this, and there are even more opinions on which is best.
Some people will tell you that a good hardwood that is cut so that the grain runs a specific way is the best option. Others will insist on using plywood or MDF because they are less prone to expansion and contraction. I have heard that plenty of people find success by buying a cheap plastic cutting board and cutting strips out of it. There are also some companies that sell adjustable runners that you can dial in to fit your miter slots perfectly. Obviously there are lots of options and I have no idea which one, if any, is the best.
Last year when I helped clean out my grandparent’s old house, I came across a few four-foot square sheets of what I believe is PVC plastic in varying thicknesses. I saved them and added them to my collection of materials knowing that eventually a project would come up where I needed them. I decided to use this material as the runners for my sled thinking that they will be impervious to any expansion or contraction, they will resit ware longer than any piece of wood and they would probably have a more slippery surface to aid in sliding down the miter tracks.
Step 2: Cutting Precise Runners
I ripped a strip off the edge of my plastic sheet that would be wide enough for two runners, then I cut the stip in half. I used a calipers to get a precise measurement of the miter slots, which was three quarters of an inch on the dot, then I set my fence to a hair over that. I wanted them to be oversized so I could sneak up on a perfect fit.
I cut a strip at that width, then tested the fit in the miter slot. As expected this first one was too big. I nudged the fence over just slightly, ripped the strip and tested it again. This time I could get it to fit, but it was quite tight and didn’t slide well. This is exactly what I was looking for, so I ripped the second strip to the same size. I actually cut four runners while everything was set up, knowing that I had more sleds coming up in my future and I didn’t want to have to dial this in again next time.
I hand-sanded the edges of the runners with 220 grit paper until I had the EXACT fit I was looking for. They slid back and forth effortlessly, but had no discernable play side to side.
Step 3: The Fences
With my runners ready to go, I switched my focus to the fences. Once again there are lots of possibilities here for materials, but the main focus should be on something that will not move and warp once you have the fence set square. Some people do this by laminating several pieces of plywood together to get one really thick piece. For me, I had a huge beam of rough-cut cedar that had been drying for close to 10 years. I figured this would be pretty stable, and it has the added benefit of being a pretty light-weight wood, so my sled wouldn’t be too heavy once it was finished.
I used a jointer and planer to get the two fence pieces perfectly flat, square and down to the thickness I wanted. Then I used the table saw to rip them to what will be their final height and cut them to length. I tipped the blade on the table saw to 45 degrees and shaved about an eighth of an inch off one corner. This creates a small recess in the back fence. Without this recess, the dust gets trapped in between the fence and the workpiece and will throw off the cut. With the recess, the dust slides harmlessly out of the way and keeps your cuts more accurate.
Step 4: Sled Body & Sizing
For the main body of the sled I used three quarter inch MDF. The overall size I am going for is pretty arbitrary. I wanted it to be big, but let the materials I had on hand dictate the specific dimensions.
Step 5: Attaching the Runners
The first step in assembly is attaching the runners to the body. I put several washers in the miter slots to lift the runners up just higher than the surface of the table. Then I ran a thin bead of CA glue down the entire length of the runners. This just needs to be enough to hold the runners to the body while you flip the whole thing over. Make sure you don’t use so much that there is squeeze out. You wouldn’t want to glue your unfinished sled to your table saw.
I locked the table saw fence down then used it as a reference to push the MDF sheet against. This way I could slowly lower the sheet down onto the runners while keeping everything lined up and as square as possible. With it set in place, I pressed down on the runners to make sure the glue made contact, then I walked away for a few minutes to let the glue set up. Most of the time I use accelerator with CA glue to speed up the process, but in this case, I really didn’t want to use any on the MDF, since MDF sucks up moisture like a sponge and I was afraid this would hurt the flatness of my sled.
Once the glue dried, I very carefully pulled the runners out of the miter slots and flipped the sled upside down. I drilled pilot holes every few inches along the length of both runners using a flag on my drill bit to make sure I didn’t drill all the way though. Then I used a counter sink bit on all the holes to make sure all of the screw heads would be recessed below the surface of the plastic. After driving in a bunch of three quarter inch screws, the slides are locked down for good.
Step 6: Perfecting the Fit
I flipped the sled back over and put the runners in the miter slots to test how well they slide. They moved, but they were binding up just a little bit, so it took too much effort to push and pull the sled. I flipped it back over then used a scrap of wood with a square corner wrapped with some 220 sandpaper and slid it back and forth along both sides of each runner. The fit was already so close to perfect that I didn’t want to remove too much material, so I only made a few passes before flipping it back over and testing the fit. This time the sled moved back and forth effortlessly, but there was ZERO side-to-side movement.
Step 7: Attaching the Fences
Moving on to the fence, I lined up the right corner and made the back of the fence flush with the base of the sled. This won’t be perfect, but it’s really close so it’s is a good place to start. I clamped the pieces together, then drilled a pilot hole from the bottom and ran in a screw to hold this corner in place.
I needed to cut a reference line in the MDF by raising the blade up through it, so I had to temporarily remove the riving knife from the table saw. Then with the saw running, I turned the crank until the blade just started to poke through in the middle of the board. Pushing on the base, not the fence, I slowly slid the whole thing forward until the blade had cut right near the fence.
I grabbed my biggest square and referencing off the cut line, I pivoted the fence until it was as square as I could make it. Then I clamped down the left corner, drilled a pilot hole and ran in a screw.
The front fence doesn’t have to be perfectly square to the blade. So I just flipped the sled over, lined up the back edges of the fence and the MDF then screwed it in place, putting a screw in each end, as well as close to both sides of the saw line. This way none of the parts will move around when I cut all the way through the MDF.
Step 8: Perfectly Aligning the Fence
Here is where we start to test and adjust the rear fence to get it perfect. I am using a commonly known process called the 5 Cut Method. In essence, you take a scrap of wood and cut off one side, then you put the freshly cut side up against the fence and cut the next side. You continue to do this until you get all the way around then cut roughly a one-inch strip off the side you started with.
Make sure you mark the front and back of that strip, then measure each end to see how different they are. At this point, some math is involved - and since I’m not good at math and can’t in good conscious try to teach someone else how to do it. Here is a link to the document that I used to to help walk me through the process.
If you do everything correctly, you will eventually come up with a number that tells you exactly how much you have to adjust your fence by to get it square. To make my adjustment, I found a feeler gauge that matched the number I came up with. I have to move the left side of my fence forward, so I put the gauge up against my fence then put the point of a carpenter’s pencil against the gauge and clamped it down.
I removed the screw from the underside of the fence and carefully nudged the fence forward until it just barely touched the tip of the pencil. Then I clamped the fence in that position, drilled a new hole and ran in a screw.
With the new fence position locked in, I performed the test again. This time I had reduced my previous error by more than half, but I still wanted it to better, so I just repeated the process again. It took me three times before I had my fence as precise as I wanted it, but you could keep doing it as many times as it takes to make you happy.
Step 9: Lock It in for Good
With my fence dialed in, I flipped the sled over and put screws in both the front and back fences every few inches to keep them from moving around. I made sure to have screws close to the cut line, but not so close they were in any danger of touching the saw blade. I rubbed paste wax into the bottom of the sled and over the runners to help reduce friction and keep it gliding easily over the saw.
Step 10: Adding a Safety Feature
The final touch was adding a bit of safety to the sled. I took a scrap block of cedar and glued it to the back of the fence. This way when the blade passes through the fence, it’s contained inside this block of wood and doesn’t present a danger to my fingers. I only used CA glue when mounting this block, because I haven’t decided if this is my permanent solution to this problem. If I change my mind, I can just tap this off with a hammer and do something else.
This is the nicest and most precise crosscut sled that I have ever had in my shop, but it is still very basic by comparison to some the the sleds that are out there. Just check out this one from Nick Ferry. I left the top of my fences flat and square just in case I want to install a t-track at some point. A t-track would be useful because it adds some modularity for adding other jigs or a flip stop to the sled. If you knew this wasn’t something you wanted, there are other shapes you could make your fence in.
A popular one looks a bit like an elongated oxbow where the highest point is just over the blade line to hold everything together, then it sweeps down so the rest of the fence is at a lower maximum height. This design looks pretty cool, and it also makes it much easier to get your hands over the fence and hold down your workpiece.
What I’ve made here is pretty much just a crosscut sled in its purest form. No frills, just a large capacity, durability and precision. If you’ve never made a crosscut sled before, you NEED one, and this is a great place to start.