Dado Blade Accuracy

[Joe Austin]

I have never used a dado blade before and just bought my first. It is a Freud 8" SD208
I set it up according to the chart that came with it for a 3/4" dado. (both outside blades and 4 - 1/8" chippers, no shims)
After making a test cut I found the dado was 1/32" light.

Is this common and I just need to add a shim or is something wrong with my setup or the blades themselves.

Also, there are no sizes marked on the differnt size shims and the chart really isn't clear about which ones (even if they were marked) should be used for differnt sized dados.

Is this chart supposed to be accurate or is it just a basic guide and it is expected that adjustments will need to be made.
Thanks, Joe

[Brian Kent]

One of the chippers is 3/32" thick instead of 1/8 or 4/32. I followed another Creekers advice last year when I got mine and used a dial caliper to measure each one and write the size on the chippers with permanent black marker. I was surprised how accurate it was.

[Tom Veatch]

...
Is this chart supposed to be accurate or is it just a basic guide and it is expected that adjustments will need to be made.
...

The chart is a guide. Adjustments will very likely be necessary to get "perfect" fits.

I believe I have the same or, at least, a very similar dado set, but mine cuts much closer to the chart measurements. If your's is the same as mine, note that the chippers come in two different thicknesses. One is 1/32 thinner than the others and is intended to be used for cutting dados to match the 1/32 undersize plywood that has been supplied for the last several years.

It almost sounds like your stackup contained the thin chipper so the resulting dado was properly sized for "3/4" inch plywood.

[Brian Kent]

Correction on my last post.:rolleyes:

I just realized I had the 508 set instead of the 208.

The 208 has both 1/8" and 1/16" chippers, so the increments should be in 1/16", not 1/32".


I'd still measure and mark, but there might be something else going on that makes it 1/32" off.

[Tom Veatch]

Just went and looked at my set. Model number isn't shown anywhere, but the case is labeled "Freud Super Dado". A Google search turns up a Model SD508 that seems to be the one I have. It contains 6 chippers, one 1/16", one 3/32", and four 1/8" referred to in the chart as, respectively, C, D, and E. The chart refers to the outer blades as A and B.

Joe, the product descriptions for the SD208 shows it with 5 chippers (4 @ 1/8" and 1 @ 1/16") and doesn't have the 3/32" chipper. If you have the 208, I have no explanation for the undersized cut. Mine cuts very close to the dimensions given in the stacking chart. But, shimming is still necessary in some cases to tweak the dado width.

[George Bregar]

This is why I always stack less than I need, and sneak up on the cut testing it each time.

[Bruce Page]

The Freud SD508 is a very good dado set. That said, I always use a pair of dial calipers when setting up my dados.

[Ed Peters]

to know the exact width of cut you will get from just the two outside blades. After you know that, everything else is just simple math. For instance, on my current set, the two outside blades produce a dado that is .2" wide. To get the proper size dado stack, I just subtract that from the actual thickness of the wood I want to fit into the dado and I then know how much to add between the blades with a combination of chippers and shims. A little tip here. I always add another.02" to the stack total so that it is a nice slip fit and not a press fit. Still just as strong but not as frustrating. And, yes I know that the novices will ignore this tip until they have hammered a few line on line dados together or hammered them to smithereens. The light is slow to come on sometimes (I was also a perfectionist about the correct dado stack once upon a time) but it will eventually.

Ed

[scott spencer]

You can dial it in using the shim stock.

[Todd Burch]

Even if it was perfect, it won't be after you sharpen it for the first time, so get on with cutting your dados.

Todd

[Todd Burch]

Think of it this way. Perhaps it makes a perfect sized dado for plywood. ;)

Todd

[Jim Kountz]

I always end up using shims to get a perfect fit, even if they do cut a perfect 3/4" dado its not always the case that your stock will fit anyway so I just got used to using shims. Depends on how picky you are about fit I guess. I like them tight but yet just loose enough to assemble by hand without having to beat the crap out of them with a hammer!

[Steve Dewey]

lee vally makes a nice colored set of dado shims. Very easy to pick the right one.

[Gary Keedwell]

I always assemble my stacked dado purposely small. I run the stock through the blades and measure the dado. I then simply move my fence and run the stock through again. Perfect. I'm a hobbyist so the extra minute it takes to do it twice is nothing. This method would be perfect for the people who have recently installed their new digital fence read-out.
Gary

[Greg Cole]

As per Gary's instructions... works for me too.
Also anyone with an incremental positioner on the TS fence can do so very accurately too, not just ones with digi-readouts.;) My TS fence for example is adustable .reference block with various common size dado's and write the chipper & shim combinations in the bottom of the dado... works til ya get the blades 'n' chippers sharpened, then ya will need another one. Easier than trying to remember I need 3 of the 1/8" chippers, this shim, that shim... cut, measure, readjust, cut again, re-re-measure.


Greg