Problem with miter sled

[SwingKing]

I've built a bomber style miter sled from a Shop Notes plan, but I'm having a problem. I've set the angles on the fences so they appear to be correct, but now the cut itself is not straight. When I put a straight edge against the cut, there's a little crown in the center (from front to back). I also seem to have just a touch of a twist in the cut, because the cut appears to be perpendicular to the face at front end and slightly off at the back. It appears to be doing this with both fences.

I'm out of ideas so I could use some help. I added the clamp because I thought the piece might be moving, but it didn't help. Could I be getting a deflection in the blade? The sled seems pretty solid in the miter slots, but I suppose that could be a problem as well. It' s just so darn consistent, so it seems like something other than random slop.

Any ideas?

Some pics of the jig:

[Sam Conder]

Just at first blush, it seems that your miter slots may not be parallel to the blade. Have you measured them to see?

[cgallery]

Try feeding very slowly. If it is deflection, feeding extremely slowly should prevent or reduce the problem.

Also, how sharp is that blade? It seems like there may be some buildup on it? If there is pitch on the blade, and it is dull, I'd suggest trying another blade.

[cgallery]

Oh, and another thing... How much of a crown are you seeing. Sometimes I'll use my Starrett square and see a little tiny bit of light under the blade. But when I hold the joint together it is fine. Have you tried making a small sample frame and seeing how it comes together?

[SwingKing]

Also, how sharp is that blade? It seems like there may be some buildup on it? If there is pitch on the blade, and it is dull, I'd suggest trying another blade.

I tried swapping the blade and and that fixed the problem. It was in worse shape than I thought but I wouldn't have expected it to have that type of behavior.

Now I need to do some searches on blade cleaning and sharpening.

Thanks for the help!

-- Ken