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  1. #1
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    Freud SD508 Dado Set Accuracy

    I am using an undamaged and sharp Freud SD508 dado set (on a 3HP General 350 cabinet saw). I use it now and again for 1/2" box joints in ¾’ stock and for off-sized plywood. It has worked fine in those applications. The other day, for the first time, I needed to plough for some T-track extrusions. To be safe, I first measured the Lee Valley T-track material at 3/4” wide. As such, I stacked the dado set accordingly. The result was an exceedingly sloppy fit. It was an easy 1/64” too wide.

    I went to work making the strips needed to fill the gaps and save the drill press table fence I was making. With the fence saved, I moved on to discovering why the dado set was unable to plough a clearly standard width. Suspecting first that I had a blade or a chipper cockeyed on the shaft or debris in between blades, I removed the setup, cleaned the mating blade surfaces and arbor face and remounted the stack. No change. A 3/4” setup (A-E-E-E-E-A) produced a groove that was an easy 1/64” too wide. I then looked at the saw. My arbor and flange runouts were about +-.0015 as best as I could measure. Moreover, my saw has been preforming quite well with my other Forrest and Freud blades.

    Freud is telling me to use the supplied shims to achieve desired widths, but I’m having trouble understanding why an obviously standard with cannot be achieved without the tedium of shimming. Sure, I've used the shims for plywood and other off-sized material thicknesses, but 3/4" x 3/8" extrusion seems a standard width that would not require odd chippers and or shims for a snug fit.

    Has anyone else had a similar experience and/or can anyone shed any additional light on this? Are my expectations out of line?

  2. #2
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    Re: Freud SD508 Dado Set Accuracy

    You may wish to check to see if there is any wobble or runout in your arbor — either due to a bent arbor or because of debris on the arbor flange — as that slight wobble will result in an enlarged dado slot as well even if the stacked set is otherwise accurate. Also check that the dado blade is perfectly parallel to your fence as, again, any error will result in a wider than expected dado. If the dado set itself is off then carefully measuring the distance between the two outside teeth should reveal that same error if it is the dado set at fault and not another cause (ideally you should use a nonferrous or composite caliper for this measurement to ensure that you can not accidentally chip a carbide tooth, but a steel caliper is fine so long as you are careful and gentle while measuring).

    That said, test cuts should always be performed first with any dado set, and then the set adjusted and shimmed accordingly to achieve the desired final fitting — this avoids the poor fit issue by tailoring the dado width to the task precisely versus a specific measured value.

    However, in my own experience the Freud dado sets are usually pretty close to exact as-is, but it still pays to make test cuts first to verify fitment. Do also be aware that not all the chippers are the same thickness (there are also 1/16” and 3/32” chippers) as you will only want the 1/8” chippers for 3/4” based upon the nominal stacked widths.

    Best of luck and let us know what you discover the cause to be.

  3. #3
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    Re: Freud SD508 Dado Set Accuracy

    I don't think you can say "1/64" here. People get upset.

    Just kidding. Sort of.

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    Re: Freud SD508 Dado Set Accuracy

    You should be using 2 x 1/8" outside blades and 4 x 1/8" chippers = 3/4" (A-E-E-E-E-A).

    I have the Freud SD206 dado set and have never experienced the inaccuracy that you're experiencing. I have to remove the inside arbor washer and replace it with the thinner outside arbor washer nut to get a 3/4" stack set up with enough threads on the outside of the arbor shaft for the arbor nut and a tight fit (no outside washer now). Without the nut being fully engaged on the arbor shaft you can get some wobble in the setup.

  5. #5
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    Re: Freud SD508 Dado Set Accuracy

    Thank you all for your input.

    My arbor and flange runout is well within General’s specsaccording to my dial indictor. There is no damage to the arbor shaft. According to my TS Aligner’s dial indicator, my fence and a 10" blades are parallel to my miter slots. Cuts with other blades are clean and free of burn. I fully grasp the issue of varying chipper widths. For a 3/4” groove, Freud calls for the two outside blades and (all) four “E” (1/8th) chippers, which is what I stacked. This is easy to confirm, as the remaining chippers are clearly differing (smaller) sizes.

    I fully agree with and prescribe to test cut procedures, but I certainly expected very close to 3/4” from a 3/4” stack. Instead, the 3/4” extrusion slops around in the resulting plough.

    I suspect now that:

    • One or more of the outer blades and/or chippers is something less-than-flat
    • One or more of the teeth on one or more of outer blades and/or chippers is fat


    I will continue my investigation and will be grateful for additional thoughts.
    Last edited by Ed Fasano; 09-13-2018 at 01:37 PM.

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    Re: Freud SD508 Dado Set Accuracy

    MIKE the track, being everything is made in china,most likely mm.

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    Re: Freud SD508 Dado Set Accuracy

    Quote Originally Posted by Skymaster View Post
    MIKE the track, being everything is made in china,most likely mm.
    What is that cryptic post supposed to mean? Freud Dado sets are made in Italy I thought.

  8. #8
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    Re: Freud SD508 Dado Set Accuracy

    Jeff, I believe that Jack was referring to the Lee Valley T-track, but the OP stated that he measured it at 3/4".

    My suspicion is that one of the inner E chipper plates (or more than one) was mis-aligned with a tooth from an adjacent plate touching a tooth on that plate, or a tooth adjacent to the outer plates was not in a gullet on the outer plates. Either of those conditions will cause the stack to be wide. The OP should measure each chipper's teeth and I'm sure he won't find a wide one in the bunch. The plates must be aligned so no teeth are touching, but they are designed with overlay so the bottom of the dado is flat. I have an SD608 dado set and it cuts exactly on the money. JMTCW.
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    Re: Freud SD508 Dado Set Accuracy

    Quote Originally Posted by McRabbet View Post
    Jeff, I believe that Jack was referring to the Lee Valley T-track, but the OP stated that he measured it at 3/4".

    My suspicion is that one of the inner E chipper plates (or more than one) was mis-aligned with a tooth from an adjacent plate touching a tooth on that plate, or a tooth adjacent to the outer plates was not in a gullet on the outer plates. Either of those conditions will cause the stack to be wide. The OP should measure each chipper's teeth and I'm sure he won't find a wide one in the bunch. The plates must be aligned so no teeth are touching, but they are designed with overlay so the bottom of the dado is flat. I have an SD608 dado set and it cuts exactly on the money. JMTCW.
    Thanks Rob. I have the same suspicions about misaligned blade teeth. The Lee Valley T-tracks are usually 3/4" w as stated by them.

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    Re: Freud SD508 Dado Set Accuracy

    Are the teeth on the outside blades off set? If so you may have them reversed.

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    Re: Freud SD508 Dado Set Accuracy

    Quote Originally Posted by JohnnyR View Post
    Are the teeth on the outside blades off set? If so you may have them reversed.
    Bingo, ladies and gentlemen, we have a winner. I mark my outers as to which is right and left. They come off the stack in the order they go on the saw. Always make a test cut when using dado set.

  12. #12
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    Re: Freud SD508 Dado Set Accuracy

    I have the Freud SD608 dado set and the teeth on either face of the blade appear to have the same offset. Right and left blades aren't marked but you can tell by the direction of the teeth and rotation of the blade when installing onto the arbor shaft.

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    Re: Freud SD508 Dado Set Accuracy

    I suspect that John hit the head on the nail but I'm curious. Have you actually measured the width of the dado stack? Or are you just measuring the dado it creates? Might be worth comparing them. If the dado is wider than the stack measures, I would be looking at run out or possibly an out of square situation.
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    Re: Freud SD508 Dado Set Accuracy

    FYI, I put my Freud SD608 dado stack on today out of curiosity. It mic'd at 3/4" and a 3/4" w dado in a piece of wood also mic'd at 3/4" wide along its length.

    I'm curious to hear from Ed Fasano and what he's found with his Freud dado set.

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