# Can I ask about crosscut sleds?



## rcp612 (Mar 25, 2008)

I just built a small crosscut sled to aid me in box building. I used ½” phenolic faced plywood for the base with hard maple for the fence and Incra miter sliders. It’s only 12” deep since I never use lumber wider than 8” to 10” anyway.
My question to all the experts and users of crosscut sleds is: How precise should I expect to get this set up?
After 6 tries using the 5 cut method, I have 1/64” or .0145” difference in a 8” cut. Is that considered close enough?
I just want my boxes to come out square along with some small molding I use on some styles I build.
Thank you all in advance for your thoughts on this.


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## Hammer1 (Aug 1, 2010)

The five cut method gives you five chances to make a slight mistake. It also put five times the use on your blade. Phenolic faced plywood can be slippery and so can a plain wood fence. If your work can slip or your blade dulls, you'll never be able to be sure of the sled's accuracy. Glue a strip of sandpaper to the fence, make a cut and check the cut with an accurate square by holding up to the light and sighting for any light showing where the square blade and the square head make contact with the cut piece. Even a small piece of dust or hair raised by the blade will throw this off, so keep things clean. The edge of the work piece that goes against the fence has to be straight and this is the edge you want to reference the square to. If you can't see any light, your sled is dead on. Many folks think they have an accurate square but many are not. A good 6" engineers square is a shop must have. 

We have to assume that your saw is properly tuned, a reasonably decent saw and a quality crosscut blade in excellent shape, no slop in the miter runners. You didn't say if you are using two or one Incra slider. You can have some slight lateral movement with only one slider. You'll be chasing your tail if the saw isn't properly tuned and the blade in good shape. When making the test cuts, if there are differences between different test cuts, one or more of these issues needs to be looked at. You should be able to make cut after cut on a sled and have every one come out with no light showing. Setting up the fence should be as simple as placing the square against the blade. When simple doesn't work, there is something else at play.


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## Jory (Feb 19, 2012)

I believe you can get greater accuracy than 1/64" with a crosscut sled. You may have introduced some error if you cut the Incra slides to the 12" depth of your sled. The longer the slides are the less play they have in the slots. The way I made my sled was to put the slides in the slots put some glue on them and rest the sled on top. This was of course just temporary attachment but it did allow me to be sure that the slides were precisely aligned and the sled would not cause binding. After the glue set I screwed the slides to the sled. I agree with the comment about using sandpaper on the sled fence. Sticky back 220 grit paper does a good job holding the wood in position. Lastly it is a good idea to have the fence slightly undercut were it attaches to the sled. This slot provides a place for sawdust. Just a slight amount of sawdust can mean that the second and third pieces cut may not be quite at 90 degrees.


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## MTL (Jan 21, 2012)

Was the 1/64th the diff from end to end on the cut strip? If so your error is 1/5th of that for a single cut over the length of your test piece. That is pretty good if so. If your error was 5/64ths ene to end on the strip then you should try to dial it in a little better.

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## rcp612 (Mar 25, 2008)

Thank you for the input and, most importantly, the answer!:thumbsup:
I forgot about dividing the differential by 5, which would mean I'm only off by .0029".
And, no, I did not shorten the Incra miter sliders Jory. But I was somewhat disappointed in their design. You must have both adjustment areas in the miter slot before they will work correctly which, IMO means, that the 7 1/2" c-c is too much. So, I have them set forward by 2" to allow them both to be engaged and still keep my sled behind the blade. By the time the adjustment areas go past the end of the slots, my cut is finished. Sort of make me think the runners from Micro-Jig would be better if they were not so short.


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## H. A. S. (Sep 23, 2010)

There is no reason you can't build a crosscut sled to within .001-.002. The more accurate, the better.


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## oldmacnut (Dec 27, 2010)

I bought the incra build it kit, then bought a few other accessories for it, then got some 5/8's mdf, duplicated a few of the build it panels so I have zc panels for various blades, for miters, etc. Was the best 150.00 I ever spent.

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