Just made my first MDF crosscut sled. Help!

[Matt P]

I used the technique where you put the oak runners in the miters (with cardboard shims to make them tight). Glued on the sled. Looks good, but it doesn't slide easily. Feels very tight. D'oh!
Do I sand sharp edges along the oak runners? Do I shellac and wax the bottom?
Thanks in advance! This forum really helps me.
Matt

[Bill Huber]

I used the technique where you put the oak runners in the miters (with cardboard shims to make them tight). Glued on the sled. Looks good, but it doesn't slide easily. Feels very tight. D'oh!
Do I sand sharp edges along the oak runners? Do I shellac and wax the bottom?
Thanks in advance! This forum really helps me.
Matt

I would chalk the runner and see where they are dragging and then go form there. It could be a high spot or it could be one is to wide or not spaced right.

I did put a finish on mine and then waxed it, but I will say that I have now gone to aluminum rails which I like better.

[Stephen Edwards]

I used some scraps of 100 year old hard maple barnwood that I sized to the right size. It's just a tad loose in the slot (we're talking 1000ths). I keep the pressure on the sled to the right as I'm sawing it. Perfect 90s every time. Mine is set up for the slot to the right of the blade. I put a coat of clear spray poly on it. Once in a while I'll spray a dry film lubricant on the bottom of the sled and in the miter slot on the saw.

[Denny Rice]

I second waxing the runner of the sled. It helps a lot.

[Chip Lindley]

Um....you glued the runners to the sled? Perhaps your wood runners did swell or distort just a bit with absorption of moisture from the glue? Hitting them gently with a sanding block on all sides will probably free them up in the saw's miter slots.

Remember that any finish adds a few .001s of an inch to the dimension of your runners. Relieving a binding runner is one thing. Making a runner run without play in its slot is another thing. There are many techniques to take up slack with a loose runner. Perhaps the subject for another thread, altogether.

A coat of wax should suffice on the runners and slots to allow smooth sliding, IF everything else is in alignment and not binding.

[Jeff Bratt]

You can get an idea of where any binding might be by starting with the sled mostly off the table, and as you slide it forward noticing exactly where it starts to bind. Slide it all the way off the back also. Some chalk or pencil marks on the sides of the runners can help identify where a high spot might be rubbing. A scraper, shoulder plane or sandpaper can gently trim the sides of runners. Be very careful - the difference between tight and sloppy is only a few thousandth's of an inch.

Since you glued on the runners, waiting several days to make sure there isn't going to be more shrinkage would be prudent. It's much easier to take a little off than to put it back on. Except that a finish will add some thickness to these (or any) surfaces. Once you're happy with how the runners fit, then wax on the runners and sled bottom should make it slide very nicely.

I use screws to attach runners. Put the sled on the table, runners in the slots just like you did, but then carefully mark and drill the runner to place one screw on each end of the runners. Then make sure everything is aligned. The runners are made extra long so they can be moved slightly if you have to try again. Finally, add more screws from the top or bottom of the sled as desired to hold the runner in place along its whole length.

[John Keeton]

I second all that has been said, but would add that time and use will help a lot. After finishing my sled, it was a little snug (oak runners), but before waxing, I ran the sled back and forth on my TS 40-50 times and it made enough difference to satisfy me. Since using it more, it has become much easier to use. Personally, I would give it some time before taking off wood you cannot put back on.

[Alex Berkovsky]

Matt,
This has nothing to do with solving your problem and I am not sure how new you're to woodworking, but just wanted to add something very important. Make sure you tune up your TS before making the sled. The blade must be parallel to the miter slots before making the cut in the sled. BTW, like Bill, I also bought aluminum rails for my next sled.

[Sue Wise]

I just made my first crosscut sled also using MDF. I also had the same problem, which I understand is usually what happens. (However, I screwed my runners on.) I did two things, first I took a shoulder plane and give each runner a few swipes. This loosened it just a bit and then waxed it. Now, it slides well without being sloppy.

-Sue

[Rob Cunningham]

I agree with waiting a few days before removing any material from the runners. Also, for safety, I would screw the runner to the sled. You don't want to have a glue failure while pushing your sled past a spinning blade.

[Mitchell Andrus]

I made my runners a bit undersized and use small screws to size the runners to the channel. Wear is easily made up with a slight turn of a screwdriver.

[Stephen Edwards]

The main problem that I encountered with my first Cross Sled was this: The miter slot on the right side of my blade isn't the same width the length of the slot! It's a wee bit narrower toward the back end of the table. My saw is an older Ridgid Contractor's saw. Short of removing the table and taking it into a machine shop, I don't know of a solution to that.

Someone gave me a Delta miter gauge, threw it in with another tool that I bought from them. It's one of the gauges that has the little set screws in the bar that enables one to remove all the slop between the bar and the slot. I adjusted the front set screw of the bar to perfectly fit the front of the slot. As I would push it through the slot it would stick at the back end of the slot. To test in order to be SURE that was the problem I lifted the back end of the gauge off the table with the front end of the bar still in the miter slot of the table. As I would push it through, sure 'nuff the bar would stick toward the back end of the table slot.

So, I aligned my blade and everything else...fence, sled, etc. with the right edge of the slot. I've learned to compensate for that wee bit of slop by keeping pressure towards the right of the slot when I'm pushing the sled through. Once I got used to that, no big deal and I get perfect 90s every time......even on 24" wide panels.

Thought it ain't a perfect world, there's usually a way to work around small problems; in fact, several ways!

[Greg Hines, MD]

I used UMHW plastic for the runner in my crosscut sled, and screwed it to the bottom. The plastic is slippery, but also, by tightening the screws just a hair, you can expand it to fit your miter slot perfectly.

Doc

[Alan Schwabacher]

If you have one, a card scraper can work better than a sanding block for trimming the runners to fit. They fit into the corners well, can trim off very small amounts in well controlled places, and don't leave grit that could wear the miter slots.

[Joe Chritz]

You can also undersize the runners a few thousandth's and then sink some screws in the side to act as an adjustment for the runners.

Now that I have access to a surface grinder all my future ones will have steel runners but the maple on my main crosscut sled works great.

I have noticed now that the humidity is down it is a bit easier to slide than during the summer.

Joe