Dado advice needed

Hi Everyone

I'm thinking about setting up my vintage RAS as a dedicated dado machine. I know some of you have done this.
My question relates to power and choice of a dado head. The old saw is rated at 9 amps, .75 hp and hasn't seemed overly powerful in the small amount I've used it for crosscutting hardwoods. Should I go with the 6 inch dado, or do you think it will handle an 8 inch setup?
The most common use I can think of would be cross cutting shallow dados for shelves etc.

Any advice is much appreciated, as always.

I have an 8" on mine{2hp 12amp}, but the 6" would work just as easy and be a tad easier on the machine...Quality of cut is dependant on the blades themselves. I've never used mine for deeper cuts than 3/4 -7/8", so no real advantage on that front one vs the other...my 2 cents FWIW.

a couple of more thoughts...the 6" may require the saw body to be lowered so much, as to allow the fence height to become a problem...
and a safety point...be aware of the dado lunge as I like to call it...biting a lot more lumber can cause the blade to jump towards you, just be alert and pre-parred to pucker up if it catches you off guard

I used an 8 inch dado on my ancient Sears RAS until I got rid of it to make more shop room. Worked fine; not an extraordinarily powerful motor. Remember you are doing a climb cut with a RAS, and a Dado blade takes a big bite, so be prepared to control the saw.

Did this very thing a few years ago. Also an old saw. Learned a couple of things. Have an 8" stacked dado cutter set. Tried it. It was very grabby and hard to control. Switched to a 6" set.

Link here. http://www.freudtools.com/index.php/products/product/SD206

It has the safety tooth set. Huge difference in the grabbiness. Reduced the height of the fence to 1". Plenty high enough. No interference with the fence. All that and less an US$100. Now it is a pleasure to use, and feels much safer.

I had that same type saw, and used it with a dado often (8"). It wasn't too bad, but a 6" set would have been less of a struggle. I do think Ken's point about how low the motor may be is something to consider. Maybe using an 8" set with a smaller cut (say, 1/2") and making multiple passes might ease the load. You could also consider getting an Irwin Dado set, it uses fewer chippers, hence less weight (the chippers have 1/4" wide teeth, and you put an 1/8" spacer between them...I'm sure this is done for cost reasons).

I have the Ridgid saw that comes with a folding table. Sounds like I should get a 6" blade, as I cant see myself making a really deep dado?

The 6 inch blade doesn't have a lot of distance from the arbor to the teeth, and with a large arbor nut/washer, large RAS motor, or fence, the depth of cut can be far less than you expect. Remember the dado blade is often used to cut tenons and other things that are deeper that a simple shelf dado. I expect that is why 8 inches has become the "norm" for most dado blades.

I have never heard of a power problem with dado blades that couldn't be fixed with a slower feed rate.

The larger diameter (in theory) would give a smoother bottom to the dado.

Thank you all, for the thoughtful comments and advice.
I bought the 8" Freud set this week, Carol's comments notwithstanding. If it's too nasty I can use it in the TS.
I played with the setup a little, but I'm sourcing some different arbour washers and nut (current brass one, probably not original and abused by Visegrips for 60 years, is thicker than it needs to be)
I'll post some pics and a comment over the weekend, hopefully, once I've had a chance to get it set up for a test.
Thanks again.
Peter