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I recently completed a project which required lap joints to be created which were 3" wide. I was using 2x4 stock. I used a dado set to accomplish the cut.
The question is the surface of the cut is rough and I was wondering if there is a method to cut lap joints as efficiently as with the dado set that produces a smoother surface. Perferrable using a dado set rather than a router or band saw?

I don't know how to get it very smooth, but I personally found that when I upgraded to a more professional (which also means more expensive ) dado set, the result was much better. My dados look better than rough sawn, don't have any grooves and are generally flat but do not look like a planed surface. But, I did not experience these results until I bought the better dado.

I'm anxious to hear what others say. I have no comparison point.

Paul

mlettini wrote:I recently completed a project which required lap joints to be created which were 3" wide. I was using 2x4 stock. I used a dado set to accomplish the cut.
The question is the surface of the cut is rough and I was wondering if there is a method to cut lap joints as efficiently as with the dado set that produces a smoother surface. Perferrable using a dado set rather than a router or band saw?

I would have thought it would be easier using the table saw and using a tendoning jig. I'm not a big fan of dado sets. Frankly I get real tired real quick trying to set the right width. I would make a cut with my saw, and cut the piece free on my bandsaw or stand the wood upright using my tendoning jig and cut the mortise. Last resort for the mortise that big would be the router. In fact I would probably make repeat cuts with my tablesaw and chisel out the waste before I messed getting my dado blades out.

But the answer to your question is the more expensive the Dado set, usually the more teeth on the chippers and the smoother the resulting cut. Also size of the blades plays a part since the tips move faster the manufacture usually builds better teeth on the blade as it get bigger.
Ed

A while back someone posted about having the dado blades and chippers all ground to exactly the same diameter for a smother cut. If you call your saw blade re-sharpener for the price let us know how much, it may be worth having my dado blade reground.

Like Paul, I get much better results from my Freud 6" dado set than my first dado set. But they are spendy.

Ed's idea of using a tenoning jig would give very smooth results. If you don't have one, you'll have to purchase or make one.

I'm sure you have a block plane in the shop. You can knock of the high spots easily which should give you half laps a better fit.

Thanks everyone. I had considered the band saw and router options. Bu:) t the tenoning jig would work if the cut were not as deep. I will check the price of a better set of dado blades

mlettini wrote:Thanks everyone. I had considered the band saw and router options. Bu:) t the tenoning jig would work if the cut were not as deep. I will check the price of a better set of dado blades

There is a tread on the Dadonator a few months back, check it out.

I'm sorry to disagree with those thoughts that an expensive dado set gives smoother surfaces than all cheaper ones. For X shaped half laps or half laps inside the length of a workpiece, I have very successfully use my 6" wobble dado, set to 3/4". With speed "O". Very smooth cuts! I always use a backer board with the dado blade. I have to admit that exact width of the joint is difficult to set. I like to scribe and if I can - use miter guage stops, and always make a practice cut on scrap.

I've made quite a few half laps. Occasionally, I have even made them for the purpose of lengthening a board. (That's easier than a scarf joint)

The other method I use, for corner half laps or board lengthening is: I use the table saw and the rip blade (SS of course) and a tenoning jig (Home made). I've found the most successful method is to first saw the long with grain cut a saw width short of the cross cut - then make the cross cut, using a crosscut blade, into the kerf of the first cut.

When making the first cut, I make it to leave just a wee tad more of the wood than half. Then if the joint is proud, I can go back to the tenoning jig and do a very small (nibbling) cut taking only a fraction of a saw kerf. During this nibbling cut leave a little wood at the top of the saw blade. It can be easily removed with a chisel.

I have yet to make a half lap with a router, but with the OPR and sliding table this should be a snap!