Cross Cut Sled Questions

[Teresa Jones]

How can such a simple concept be so difficult to execute??

I machined two runners out of mahogany to fit both miter slots. I then cut a piece of 1/2 inch baltic birch plywood to the dimensions of the table top (48 inches side to side and 28 front to back).

With the runners in the miter slot, I applied double-sided tape to the top sides of the runners and then placed the plywood on top of the saw, aligning all the edges.

Removing the assembly, I proceeded to drill pilot holes for the screws to attach the runners to the plywood. The first runner attached without any problems. The second one split in two different places.

Now, the sled would not slide, because the split runner is binding in the miter slot. No problem, I removed the runner, ran it through the jointer and reattached. OK, now we get a nice smooth slide all the way through.

This morning, getting in the truck, heading for work, I notice that the plywood base is now warped at both far ends - arrrghhh!!

I need your helpful suggestions and I am willing to start all over again.

Things I am considering - using UHMW plastic for the runners and 1/4 inch MDF for the base. I think 1/2 inch MDF is too heavy?? Should the sled be smaller dimensions?

If you made it this far, bless you!!

Thanks,

TJ

[Rob Russell]

Teresa (or do you prefer TJ?),

Do you have a bridge across the end of the plywood that warped? If so, it's possible that movement in the wood pulled your plywood into a warp.

If you don't have a bridge, consider that as soon as you run the sled through your saw, you'll have 2 halves of a sled.

Here's an article that shows some different versions of crosscut sleds.

http://benchmark.20m.com/articles/Cr...ledArticle.pdf

Rob

[Ted Shrader]

Teresa -

Like Rob says, you need additional support. Mine has a single layer of plywood on the "front" side of the sled (side that hits the blade first). The "back" side has a double layer with a T track embedded. Handy for attaching a stop block for repeatability of cuts.

One other suggestion - different runners. Mahogay is kind of soft and prone to splitting (as you found). The runners won't last as long as some made from a harder wood - say maple. Also, there are UHMW plastic runners available, but I think most of the friction comes from the bottom of the sled. (I use maple.)

The runners on the "front" of my sled extend beyond the sled about 3" and are tapered for about 1½". Makes putting the sled on the saw very easy.

With a little fine tuning, you will find this to be one of the handiest tools you own!

Good luck,
Ted

[Dick Parr]

The first sled I built I used the plastic runners. DON"T

They expand when you put screws into them and then they don't run in the slots. I spent half a day fighting this. I used oak runners and had a garbage can full of plastic.

When I built the next one, a miter sled. I went out and got the metal ones that are already drilled and can be adjusted. Piece of cake.

Good luck.

[Jim Hill 2]

Sorry your having so many problems. I made mine out of 1/4" birch plywood with Red Oak Runners. I ran about a 5" bridge over the front and back edges and screwed them from under the plywood. I made pilot holes in the red oak runners and counter sinked them. I like your idea of double sided tape, but at the time I just shemed the runners and used super glue then screwed it to each end. The only suggestion I would give is not to put screws near the blade. I eventually decided to use mine as a jig for cutting finger joints and the screws had to be removed to avoid the blades hitting them. Good Luck!

[Teresa Jones]

Thank you all for your comments.

I have plenty of red oak in the scrap pile, so I will start with new runners. I made mine the length of the miter slot. I think I will add the extra length as suggested.

Should I add the front and rear support bridges before I attach the runners? I was planning on using a milled down 2x6 for that application.

Thanks for the advice about the plastic, I will steer clear!!

I was surprised the baltic birch warped, but maybe with the added weight of the bridge it will do better.

Thanks again, everyone!!

TJ

P.S. - My nickname is TJ and I do prefer it, but I answer to just about anything!!!!

[Todd Burch]

Teresa, I have a 1/2" baltic birch sled that is 6 years old. I love it. The ply was a little "warpy" when I started, but once it is screwed to my 1" fences, and was cut in the middle into two pieces, it's pretty flat. And, what flat is is not, when I set it on the saw, it flattens out.

I used white oak for the runners - it's what I had in the scrap bin that was hard. Mahogany, walnut and cherry would be too soft wearing.

For the rear fence, I used a piece of red oak, a full 1" thick, 5½" tall (or so) and the width of my sled. There is no requirement to make the sled the same size of your table, it can be bigger or smaller. I have two sleds, a big one and a small one. With the big one, I can cross cut a piece 26" wide, which handles most cabinet case parts (23¼"). Also, no need to sweat making the 1/2" ply square to the table - just make sure your runners slide nice, are not snug but not too loose, don't bind anywhere front to back, and your rear fence (if that is your registration fence) is dead on square to the blade. The front fence, or non-registering fence, can be on sideways for all that matters - there is no requirement to have it square - I just eyeballed mine, which is 1" thick yellow pine.

Todd.

[Kent Cori]

TJ,

My experience with the UHMW runners mirrors Rick's. I finally scraped them down far enough to work but I could have bought several adjustable metal slides for the effort I put into the scraping.

[Bruce Page]

I guess I'll be the rebel again... I used UHMW for the runners on my large sled and I’ve been happy with it. I used several screws in each one so that I only had to snug them and not over tighten. I have zero play, they are unaffected by humidity, and they slide like greased lightning.

[Lars Thomas]

Well Bruce,that's gotta be the prettiest cut-off sled I've seen. That's better looking then the stuff I take out of my shop. Impressive.

[Todd Burch]

Boy Bruce - what a fancy sled!! Mine does not have the rails that span the distance from the rear fence to the front fence, and, I don't think I would like them either, as they would interfere with removing cut-off stock, especially on the right side of the blade.

I like your blade guard to the back - I don't have one. I do have them on my finger joint jigs though.

Todd

[John Miliunas]

I guess I'll be the rebel again... I used UHMW for the runners on my large sled and I’ve been happy with it. I used several screws in each one so that I only had to snug them and not over tighten. I have zero play, they are unaffected by humidity, and they slide like greased lightning.

Hey Bruce, really nice looking sled you got! Question: What is that brassy looking bushing or whatever over on the left side of the sled? I see it both, from the top and backside of the sled table.

[Bob Lasley]

TJ,

I have to agree with Dick on the metal runners. I like the Incra Miter Sliders. They are not cheap, but I think the adjustment feature makes them worth the money. I have several on various sleds and jigs.

Bruce,

Woweee! That is about the fanciest sled I've ever seen. If I had something that fancy in my shop, SWMBO would be hauling it into the living room for a piece of furniture!

Bob

[Dick Parr]

Bruce, very nice looking sled. I was thinking of putting the same type of runners on mine except they would be to secure a piece of plexyglass to keep the chips from flying back into the face. Is that brace piece on the bottom a stop?

[Bruce Page]

Thanks guys,

The sled is straight out of AWW, I no longer have the issue but it was the cover story 3 or 4 years ago.

John, the brass piece on the sled is a stop. If you look closely at the first pic you’ll see a brass stop on the side of the wing, it stops the sled before the blade hits the plexiglas guard.

Todd, yep you're right, the cross braces are sometimes a real PIA! I store this thing under the crosscut table and it is heavy, the braces save my back.