Again, the miter sled and a bad video

[collinb]

I was watching this video on making a 45 degree miter sled.

 

In the video he says that what matters is the 90 degrees of the two sides for your complementary cuts and their relationship to the blade is not so important.  If that center angle is off then, once you mate the outside edges, the centers will not be in alignment.  Do people take *basic* geometry any more?

The comments reflect his error.

[Tpt life]

If your jig is skewed, always cut mating pieces on opposite sides of the jig. The angles will always meet at 90°. You are correct that some striated materials or ornate stock will not look presentable this way. The issue is only that he overstated his closing argument in my opinion. The margin for error in getting as close to the line as possible is likely negligible. It is likely even less than the possible deflection of the blade. This means you should not need to freak out, but certainly don't get sloppy and think all will end well. 

[Rapid Roger]

I almost posted here yesterday and then chickened out.

I have a sled designed the same as  Steve's and have had great results

I will agree that a full one degree difference would not be good but still if the sled is off even at a half degree from 45 to the blade and you use the opposing sides of the sled in the correct manner the corner will be 90 degrees and I don't think that the width of the frame sides would be off enough to notice for the most part.

The real secret is to get the fences at 90 to each other and cutting one end of each piece on the left fence and the other end on the right fence will ensure that you get a good fitting miter and the corner will have to come out at the same 90 degrees as the fence.

Obviously the closer you get the fences to 45 degrees from the blade the better it is but, the important part is the 90 degrees to make sure you get a tight fitting miter joint and that the frame corners are at 90 degrees to each other.

I think it is MUCH better than relying on a normal miter gauge to get a 45 degree angle and expecting a good fitting 90 degree joint on a frame.

 

Rog

[Tpt life]

A lot of guys work adjustability into square sleds. It would not be a huge deal to do some work to get the miter sled dead nuts with a little engineering. I know exactly how big a deal one degree can be. I mitered a four foot wide porch twice across five feet for a door set on the 45° of an inside corner. I spent a whole day shaving bead board back several feet to blend beads over to meet properly in the bead board ceiling. I earned a lot of respect from my boss, but my neck really hurt.