Tablesaw crosscut sled

[Travis Porter]

I want to build a tablesaw crosscut sled. I have two Incra miter slot bars, and have checked out several of the pictures people have posted, but how do you make sure you have your bars straight before you mount them so that you get a perfect 90 degree cut off?

Reason I am doing this, I am not happy with the quality of the cuts I get with my 12" Dewalt miter saw.

[DaveO]

Drop the bars in your miter slots with pennies under them as spacers to raise the height, add some double stick tape to the top of the bars. Then use your rip fence to line up the base board, set it on the bars and lift up they should be attached. Mark and drill your holes to mount the bars, the Incras have great top side adjustments so you can tweak the fit. The mount your rear fence. Cut a kerf in the rear fence and 2/3 through the base board with your chosen x-cut blade. Then square your main fence to the kerf. Install two screws in larger than needed holes in the bottom of the main fence so you can adjust it for perfectly square, and when you get it perfect add a few more to lock it in place. Once you get the fence as close as you can off the kerf, take a wide board with two parallel edges and x-cut it, flip one section and put them back together if there is a gap you are out of square by half that amount. There is another 5 cut method I have heard of but I don't know it well enough to explain. I used the first method and mine is dead on square. HTH

Dave

[DaveO]

The Incra miter sliders do mount from above and have a hex head screw adjustment system that allows you to adjust the sliders width to take up any slop in the miter slot. IMO they are the best way to make an x-cut sled, always adjustable and no seasonal movement issues. I have made two with them.
Dave

[Steve D]

I agree, I did the oversized holes on the back fence too. I'll look into the Incra runners for a future sled. I have not had any issues with the hardwood runners but I run a dehumidifier in the shop during the humid months.

[Joe Scharle]

I do it a little different. I make sure one edge (rear) is square, using my miter gage (with an extension) that is set at 90 deg to the blade, I glue one runner. After it sets (1-2 hours), I glue the other. Always maintaining squareness to the miter gage. Before the 2nd rail sets I slide the whole assembly back and forth to make sure the runners don't bind. Excess glue pops right off the cast iron of the table, if you keep it waxed. Center the sled and raise the blade while running. Then I mount the front & rear fences, squared to the blade. Glue, hold pressure and squareness for 10 min. Turn out the lights til tomorrow.
I've made at least a dozen, so to me they are throw away.
Good luck,
Joe

[Steve D]

I'm assuming the Incras mount from below. I have done them in the past with hardwood runners and screw them in from the top with the runners in the miter slots.

[Travis Porter]

I haven't looked at them in a while (had them for a month), but I believe they mount from above, but you drill larger holes to allow for some adjustment. Dave's recommendations make a lot of sense to me especially the oversized holes for the back fence as that was the piece that was causing me confusion.