double sled runners for a crosscut sled

JPG · Post by **JPG** » Tue Dec 18, 2012 12:10 pm

dusty wrote:ED, it seems to me that you have moved the dadoes 3 1/2" to the right of where they were originally located on the test sled.

What am I missing.

The distance from the right slot to the blade.

If the fence/floating table are not moved between second setup piece dado and the first sled dado cut, the sled left edge to dado(blade) dimension will be the same as the setup piece left edge to right dado(slot) dimension. i.e. the sled dado(cut) will be half the miter slot separation distance closer to the sled left edge.

Warning: Excessive thinking about this can lead to headaches!:D

P.S. BTW only the right setup piece dado/runner is 'necessary'. The left one is not actually used when cutting the sled dadoes.

Ed in Tampa · Post by **Ed in Tampa** » Tue Dec 18, 2012 2:47 pm

Does not this method assume that the saw blade is exactly in the middle of the two miter slots? That may or may not be the case with the Shopsmith.

JPG · Post by **JPG** » Tue Dec 18, 2012 2:56 pm

Ed in Tampa wrote:Does not this method assume that the saw blade is exactly in the middle of the two miter slots? That may or may not be the case with the Shopsmith.

I do not think so.

The 'setup' piece merely allows repositioning the fence an amount equal to the miter slot spacing. Any 'off center' positioning of the blade will be the same for both dados.

Ed in Tampa · Post by **Ed in Tampa** » Tue Dec 18, 2012 3:26 pm

I don't think so. Playing this on paper shows that unless the blade in exactly in the middle the dados will be off. I think???????

heathicus · Post by **heathicus** » Tue Dec 18, 2012 3:37 pm

The fence doesn't move between setting it with the jig the first time, and making the first dado is cut (which will be for the left runner).

Then, using the jig, the fence is moved left equal to the distance between the two miter slots, and the second dado is made (which will be for the right runner). Where the blade is in reference to the miter slots has no effect on the jig (unless that relationship were to change between the two cuts). So the two dado cuts will always be exactly the distance between the two miter slots regardless of what type of table this is used on.

This is one of those simple, effective, and accurate jigs that makes me marvel at other people's ingenuity!

dusty · Post by **dusty** » Tue Dec 18, 2012 5:19 pm

Please, either do a Sketchup model yourself or go to the shop and make some sawdust.

There was no slot cut in this example for the saw blade. All that Ed had done was to cut two dado slots for the runners. It is my understanding, however, that following his example, the slots will actually be only 3 1/2" apart. The slots on the Shopsmith main table measure exactly 7" inside edge to inside edge.

Once you have two runners mounted on a sled, the blade will cut wherever it is, duh. However, if the quill is fully retracted, the blade should be centered in the table insert. If it is not, the table can be adjusted to put it there.

JPG · Post by **JPG** » Tue Dec 18, 2012 5:56 pm

Ed in Tampa wrote:I don't think so. Playing this on paper shows that unless the blade in exactly in the middle the dados will be off. I think???????

'In the middle' of what? The jig only requires a single slot reference(end of setup board to slot(s)), so there is no middle between the setup 'runners'(the left jig runner is redundant).

So set yer ss up as Reible described. Measure the distance from fence to right slot inside edge. Then measure from fence to left slot outer edge. They differ by the slot separation(c-c). That is what the separation between the two dados will be if his setup board is used.

algale · Post by **algale** » Tue Dec 18, 2012 6:49 pm

The goal is to cut two dados in a sled bottom with the distance between the dados exactly the same width apart as the two miter slots.

That being one could theoretically accomplish this by creating a sled bottom of the desired size and attaching a back fence The entire sled/fence could then be clamped/bolted to the face of the miter gauge face. With the miter gauge in the right hand slot, cut a dado in the sled bottom , and then move the miter gauge (with sled/fence still attached) to the left miter gauge. By definition the two dados will have to be the same distance apart as the miter slots.

reible · Post by **reible** » Tue Dec 18, 2012 7:21 pm

dusty wrote:ED, do you actually have a dado set that will give you a dado that is the proper width for this job (47/64") or would you have to do this in two narrower cuts.

I can't get there without a bunch of shims.

I could use the adjustable dado but getting it set accurately might be an all day task.

From some years ago.

https://forum.shopsmith.com/viewtopic.php?t=2848

If you use the tables it should be pretty close on the first cut. It took me two tries to get the fit I wanted on my last project so you should have plent of your day left for other things.

Ed

reible · Post by **reible** » Tue Dec 18, 2012 7:25 pm

dusty wrote:ED, thank you for demonstrating this by using Sketchup. I have been playing again with Sketchup doing the same thing. It works really good for this.

I like to use sketchup when I want to mock something up. In this case it also made it easy to do screen captures and present the process. Once finished it also lets you make sure you didn't mess anything up. It is like woodworking without the wood.

Ed