Mike, this could be caused by a couple of things. Let's try the simple one first; measure the diameter of the dovetail bit and make sure it is actually the correct diameter. Bits are often undersized from sharpening or poor quality control. If your bit checks out ok then what you are seeing is an improper depth adjustment. By raising the bit slightly the wedge shape moves up and eliminates the gap. If your joint had been too tight you would lower the bit to loosen the fit. It is important that the wood you use for setting up your joints is the same thickness as the stock you will be working with. Any change in thickness throws off the geometry. Once you have your bit set to the correct height and are getting good cuts you should make a set up block as BJ suggested. This should be a piece of hardwood or HDPE; simply make a partial cut into the material. The next time you do your set up you slide the block onto your bit and use it to set the height... perfect in seconds every time.
If you are near the Detroit area send me a PM and I will give you directions so you can join us for our next "Sawdust Saturday".
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Mike |