I use Baltic Birch...
very good results...
last a very long time...
and it will hold fasteners too, MDF does a piss poor job of this...

 

Baltic Birch for sure. Double check to make sure it's flat when you buy it. Most of the time it is, but every once in awhile, a sheet warps. Rockler and other suppliers sometimes have precut sheets, and those are the ones I found were sometimes warped because they'd been stored vertically with pieces leaning against each other. MDF should be on the very bottom of your materials list. Good for a pattern, but the sawdust it produces is really nasty, dangerous stuff.

 

I just used some good fir ply. Fastener holding power is an issue with other materials. It needs to be thick enough to hold a screw without stripping out easily so at least 1/2". I think mine is from some 5/8" sub floor ply. At least that's how I made mine. One screw at the end to anchor the guide strip and allow it to swing so that I could square it and then firmly attach it. I tried using UHMW but it swells when you tighten screws into it unless you countersink and use pan head or truss head screws. I went with hardwood instead. And I went with a one runner design BTW.

 

I tried using UHMW but it swells when you tighten screws into it unless you countersink and use pan head or truss head screws. I went with hardwood instead. And I went with a one runner design BTW.

counterbore instead of counter sink...
clearance hole for the screw in the runner...
flathead screws tend to act as wedges and spread/split what they are screwed into...

.

 

On the design, remember the bigger it is the heavier it is... my back told me to bring that up.

 

I have made several out of ply wood. The one I have now is 1/2" melamine 2 sides particle board with one runner and fixed runner on the right side that is stationary to catch the drop off. The left side slides and only has a fence on the back with a sliding sacrificial fence like half of a router fence.
Herb

 

I always use 1/2" plywood for mine, no screws or nails, all glue fastening.

 

When I am designing things, I tend to be thinking about re-usability of bits and pieces for some future project. All glue precludes that. However, I am rethinking my design philosophy because the most critical thing about a sled is that the runners remain absolutely fixed in place after the saw kerf is made in the sled. This insures that the saw kerf will remain parellel to the miter slot on the table saw.

Have you used any plastic runners and if so what kind of glue do you recommend?

 

I made one out of BalticBirch and decided to give it up based on ease of use. Now use an extended fence faced with 220 grit sand paper attached to the miter.

 

That is a big consideration,Jon. I made one out of plywood and 2X4's front and back to do cabinet sides and doors, one time. It was so awkward and heavy I finally pitched it after a time. It worked great on the saw,but was a PITA to store and move around. Also eventually the slot got worn so that it wasn't zero clearance anymore. I think sleds are great jigs for the table saw to cross cut and quite safe too. but storing them becomes a problem at times,like all jigs. That is why a lot of guys just make temperary ones and throw them away after use.
Herb

 

@herb Stroops

Agree with you on all points there.

Managing to stay cool?.


Jon

 

Yep, got the A/C fixed. The first quote was $5400-new compressor, Secound Quote new unit $6800. Third Quote recharge unit $900. That did the trick.
Herb

 

About 10 years or so ago, I built what I considered a premium CC sled. When I finished, I had what I sought to build. However, 10 years down the road you tend to view things a little differently. The sled I biuld, to this day is rock solid, performs beautifully and does everything I could ask of it. Not bad ya might say....but, sometimes more is not necessarily better. The more bells and whistles you add, the more weight you add. Bigger is heavier (typically, especially if your using standard materials) Esthetics do not necessarily add to functionality!!!!! I tend to like to build jigs that look cool, but that doesn't mean that work any better than one built to bare bones standards. Consider carefully application and practical usage.
IMHO the foundation for a really good sled has got to be Baltic Birch ply. Second choice would be a really good sheet of oak or maple ply. Just not a big fan of MDF for this kind of application. And certainly not particle board. Longevity is always an issue with shop built jigs and i just don't see either material holding up after a few years of use. 3/4" plys work great, but there is always the weight issue. If its just a small sled, then it probably won't make that much of a difference, A medium to large sled, it'll start adding up quickly. Most of the assembly can be handled with good screws. 1/2" ply works great, ya just gotta be careful when installing T-tracks etc.... 1/8th inch isn't much to hold a screw. I prefer to go with an epoxy on 3 sides to hold tracks in place. Pretty much eliminates any flex. Dado fences into place, don't use butt joinery. .....The very best advice I could give would be to just build one. See what you like, don't like, what works for ya, what don't and consider how to improve upon the design... then build the next one based on what you've learned.

Here's a link to one of my sled builds..
https://www.routerforums.com/twoskies57-gallery/17549-crosscut-sled.html

 

That is a super nice jig you built, I missed it by about 5 years, do you still use it?
HErb

 

HEHE Thats funny,you made it to last alright. And it looks classy too. I like the hold down concept.
Herb

 

A quick MDF story. I have a 90 degree crosscut sled made from ply. For a project I needed one for 45 degrees. I figured it would be a one off so I used MDF for the base. It worked. I moved to FL a little over 3 years ago and brought it with me. I had it stored next to the back door (people size) in my garage. I had the back door open, which I usually do since it gives me a cross breeze, but had gone into the house for a drink and short break. Suddenly, it started to rain, heavy, as it does so often in FL. By the time I got to close the door the water had puddled just inside the door and the cross cut sled was in the middle of it. I had stood it on it's end and it had sucked up the water for about 3 inches of had swelled. I let it dry but, and you know if you've been down this road, it didn't go back to it's original shape. I was actually able to cut the bad section off and the sled is still usable, but I'll never do that again.

 

This thread prompted me to dust off some cross cut sled notes that I have accumulated over the last few years.