I have the 8″ Freud Super Dado set and a 10″ Jet Contractors table saw. I am trying to cut a flat-bottomed 1/2″ dado with the two blades on the outside and two 1/8″ chippers in the middle as recommended. The problem is that the outside chipper cuts deeper than the inside chipper. I tried switching the chipper offset from 90 degrees to 45 degrees, switching the two inside chippers, and replacing the two inside chippers with my remaining two 1/8″ chippers (the set comes with four). Nothing worked. In each case, the outside chipper cut deeper than the two blades and inside chipper. Any idea what might be going wrong and how I can fix it?
– Lyptus
Replies
measure
I'd try comparing the diameters of the chippers by putting them on the shaft (saw unplugged, of course). If they don't match, a call to Freud customer service would be in order. But, since you've swapped the chipper positions, they are probably OK. So, I'd check the arbor to see if you might have a damaged area at the location of the outer chipper blade. You mght be able to solve the problem by putting an extra washer on the shaft before the blades are mounted, thus moving the entire assembly over a bit.
My guess is that the outside blade is riding on the threaded portion of the arbor shaft. This threaded portion is probably slightly thinner than the inner portion of the shaft which may be unthreaded. This means that the outside blade in not spinning in a concentric circle--it's sort of wobbling. There is not much that can be done about it. Any blade resting on the threads will hang down slightly when you first install it and will be locked down when you tighten the nut. No matter where you place the blade in its rotation, gravity will cause it to hang in its lowest position. As similar situation was very common on older Craftsman saws.
If you have access to a micrometer, you can check this out by gauging the shaft next to the bearing and then at the point where the outside blade rides on the threaded portion of the blade.
How old is your saw? Is this something new? You may be able to buy a new arbor shaft.
My guess is that the outside blade is riding on the threaded portion of the arbor shaft. This threaded portion is probably slightly thinner than the inner portion of the shaft which may be unthreaded. This means that the outside blade in not spinning in a concentric circle--it's sort of wobbling riding up and down as it cuts. There is not much that can be done about it. Any blade resting on the threads will hang down slightly when you first install it and will be locked down when you tighten the nut. No matter where you place the blade in its rotation, gravity will cause it to hang in its lowest position. A similar situation was very common on older Craftsman saws.
If you have access to a micrometer, you can check this out by gauging the shaft next to the bearing and then at the point where the outside blade rides on the threaded portion of the blade.
How old is your saw? Is this something new? You may be able to buy a new arbor shaft.
My saw is around 10 years old. Just to clarify, the outside chipper (the 3rd or four placed on the arbor to make a 1/2" dado) is riding high. The outside saw blade, the inside chipper and the inside blade are all level with each other. I agree that given all that I've tried, it must be a problem with the arbor in the particular location of the outside chipper. I own an electronic caliber but not a micrometer and I wouldn't trust the caliper given the tolerances were discussing.
Aside from purchasing a new arbor, the only other option I can think of is adding a blade stabilizer or large washer on the inside of the arbor so that maybe the anomolly in the arbor would fall between two blades and therefore not effect them that much. Alternatively, is there a thin durable fabric or tape I can wrap around the arbor to perhaps tighten the fit? What do you think?
- Lyptus
Good dados are manufactured with close tolerences on the arbor hole. Any "play" will cause blades or chippers to rotate in non-concentric paths. This will cause a non-flat bottom to the dado you cut. Wrapping tape around the shaft will prevent getting the dado components on the shaft at all.
If the anomoly occurs at the same position no matter which blade or chipper is at that spot, it indicates that there is a problem with the arbor. Have you tried with each of your chippers?
Is this a recent problem? Have you used other dados and not had this problem?
Problem solved
Howie, you were right. I removed the dado blades and the initial thread on the arbor adjacent to the unthreaded section was not machined flat and flush with the other threads. Any dado blade in this position exhibits play and therefore revolves in a non-concentric circle- as you suggested. I tried placing spacers on the inside of the arbor hoping to shift the dado set enough to the outside of the arbor so that no individual blade would be resting dead center over the problem spot. That didn't work so then I tried loosening the arbor nut slightly, moving the blade in the problem position up and down by hand and then letting the blade rest where neither the bottom nor top of the arbor hole in the blade made contact with the arbor (finding the center through feel). Then I tightened the arbor nut and whalla... a smooth dado was produced.
Embarrassingly, all this trial and error took about 3 hours and my dados only took 15 minutes to cut. However, at least I'll be able to correct the problem in the future. Ideally, I would like a new arbor but I think installing a new arbor would require taking the saw completely apart so for now I'll see if I can get along with my current fix and save up for a cabinet saw purchase one day in the future.
Thanks for your help.
- Lyptus
Somthing to try
One way owners of older Craftman saws dealth with the problem was to fill in the depressed area with a two part epoxy putty like JB Weld. Thoroughly clean the area with lacquer thinner. Tape off both sides of the area you will be applying the putty to. Mix the putty well and apply it to the area. Let it dry completely (an infrared heat lamp or a hair drying will speed things up). Once hard and cured use 120 grit sandpaper on a flat piece of wood (Remember the doctor's tongue depressor?) and sand the area even with the arbor section that is unthreaded.
It is likely that the threaded area is slightly smaller in diameter but there is nothing you can do about that. At least the above will eliminate the most unevenness.
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