Dado Blade Question - Help

I just purchased a Freud SD508 8" super dado set for my Delta contractor's saw.
There is a compression washer (cupped) that normally sits between the nut and the blade. However, with this washer installed, I cannot come close to fitting the entire stack on the arbor. Even at 3/4" stack, the nut just not have any thread exposed on the outside (it seems to be snug but I would feel better if it had some thread exposed).
Is that washer necessary when using the dado blade? I would use it when it fit but if I used the larger stacks without it do you think it would be a problem?
Thanks for your help.
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That is normal. My table saw manual specifically tells me the washer will have to go when using a dado blade.
Joey

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I leave it out when making a wide stack. It has not been a problem. Ed
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You've probably noticed that the dado blade is thicker than a normal blade, anyway, so don't worry about it on any stack. On my saw it's a task to pull the blades off, since any tilt binds them on the shaft.

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Concerning Dado Blades, what does the group recommend as a good choice? For example, how does the Forrest DK08244 8" compare against the Freud SD508 8"? Is the large cost differential worth it?
Philly

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In virtually all the comparisons in magazines, the Forrest has come out on top. It has a negative hook which makes a cleaner dado, eve in plywood. Since I already have two old Freud dado sets that do a reasonable job, it will be a long time before I will find out if it is worth the extra price.
Preston

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