Varible width dadoe

[Andrew Fleck]

I was cutting dadoes in both ends of a cutting board today and got an interesting result. I normally use a dadoe stack to cut them on the tablesaw but I thought I would try something different this time as I wanted my dadoes perfectly centered in the ends of the cutting board. The dadoes are 3/8" wide and 2" deep. This time I just used a single Forrest blade to make them. I made my first pass as close to center as I could get it and then rotated the board 180 degrees and ran it through again. I continued this rotation method making small adjustments to the fence until I reached my desired width. Everything seemed to work well until I measured the width with my calipers so I could plane a piece of cherry to the correct width. This is to be inserted in the dadoe. The center of the board measures .318 while the ends are .310. It slowly tapers from .318 in the center down to .310 on both ends. I'm racking my brain trying to figure out what is causing this to happen, but I can't figure it out. Anybody have any ideas? Hopefully I explained this well enough.

[Myk Rian]

Thin kerf blade?

[Andrew Fleck]

Thin kerf blade?

Standard kerf blade. I can't figure this out and it is irritating me. I might run a test with a different blade tomorrow, but I suspect something else.

[Anthony Whitesell]

Does the thickness of the board vary (tapered)? Is the outside measurement of the board the same at both ends? If the board was thicker at one end than the other, it would result in the dado being wider at one then the other because the reference face changed when the board was turned for the second pass. It could also happen if it wasn't kept against the fence during the cut.

[Matt Day]

Blade flex since you have a blade cutting with wood on one side only?

[Andrew Fleck]

Does the thickness of the board vary (tapered)? Is the outside measurement of the board the same at both ends? If the board was thicker at one end than the other, it would result in the dado being wider at one then the other because the reference face changed when the board was turned for the second pass. It could also happen if it wasn't kept against the fence during the cut.

Thanks Anthony. You are spot on. I just measured the outside measurement and it is indeed .008 thicker in the center. It didn't occur to me that my board was not as flat as I thought it to be. Now to figure out how this happened.

[Anthony Whitesell]

I was expecting a single taper, but the triangle shape (being thick in the center) would have the same effect.

How was the board "thicknessed"? Prebought S4S or S2S stock or did you joint and plane it?

[Andrew Fleck]

I was expecting a single taper, but the triangle shape (being thick in the center) would have the same effect.

How was the board "thicknessed"? Prebought S4S or S2S stock or did you joint and plane it?

I did the jointing and planing. After glue up the board was too wide for my planer so I went at it with a hand plane to flatten it out. I guess I got a little agressive on the ends.