Dado Blades on Table Saw

[George Bokros]

My dado set will go to 3/4". My arbor though will not let me go that large and use the outside washer that goes between the outer blade and the arbor nut. Is it safe to use it that way or should I not omit the washer and make 3/4" dado's on two passes? Could I use a regular grade 8 5/8" washer that would be thinner than the one that came with the saw?

Thanks

George

[Grant Wilkinson]

You don't need the washer, in my experience. YMMV, but I've used my set without a washer for years without incident. Others may have other thoughts.

[Lee Schierer]

My dado set will go to 3/4". My arbor though will not let me go that large and use the outside washer that goes between the outer blade and the arbor nut. Is it safe to use it that way or should I not omit the washer and make 3/4" dado's on two passes? Could I use a regular grade 8 5/8" washer that would be thinner than the one that came with the saw?

Thanks

George
All of the above will work just fine as long as you get the nut tight. I can't use the washer on my Craftsman saw with my dado blade either.

[George Bokros]

All of the above will work just fine as long as you get the nut tight. I can't use the washer on my Craftsman saw with my dado blade either.

My saw is a Craftsman also. Darn short arbor.

George

[glenn bradley]

I skip the washer as well . . . unless it will fit. The outer plates on my stacks are quite thick and i have had no problems running wide dados without the arbor washer in place. Please do be sure that the nut is fully engaged (threads all the way through the nut).

[Jim Fay]

My saw is a powermatic and the maker of my dado blade says no problem to omit outside washer. I agree that threads should be thru the nut however.

[Joe Kieve]

Same on my 10" Unisaw...no outside washer. Works fine.

[Rich Enders]

On the theory that you cannot be too safe... Limit the width of the dado set to the saw manufacturers recommendation. They made that arbor just so long for a reason.

Having said that, it seems like people (including me) are always trying to stretch machine capabilities. If you are going to do it anyway, I have two suggestions for doing it better. If you are going to use a wider dado set you may still have room for using a blade stabilizer instead of the saws arbor washer. This is like a 4 or 6 inch diameter thin washer but it is a "precision" product that will more uniformly distribute the clamping forces further out on the dado blades. Stabilizers are available from Forrest, and others.

Another approach for short arbors is to make an extender. This would be a 1 inch diameter sleeve that is threaded internally to screw over the 5/8 inch arbor, and to extend the required distance beyond it . The 1 inch OD is threaded to accept a 1 inch arbor washer and nut. The blades will need to be rebored to 1 inch which Forrest and others offer. I used this technique on an original short arbored Euroshop (now MiniMax) before they got the message and built their machines to accommodate 3/4 inch wide dado sets.

Beyond safety the question remains whether adding an oversize dado set with or without an extender will over tax the motor. The load on the motor during start up and the load during a cut will tax the motor's windings, and bearings. And how many manufacturers are using over size motors? Hmmm.

The start up load is fixed by the torque required to get a dado set turning. The cutting load can be reduced by making shallower and slower cuts, but then you have to ask just what you have saved using a wider dado.

[Vince Shriver]

Seems like a solution looking for a problem. No outside washer needed.

[David Kumm]

Rich, good points. It's not just the motor and bearings but the strength of the arbor assembly and trunnions that need to be considered as well. While the tip speed of the 8" is better than a 6", I'd err on the side of the smaller dado with a light duty saw. There is a lot of spinning mass on a full dado. Dave

[jack forsberg]

the problem as i see it is that the washer/ arbor flange have re leaved centers and only bare on the outer edge of the washer flange. If you only use the nut you will distort the the saw plate. Is this a big deal on a small dado plate of 8" or less? Not likely.

Dave How is it you think a 6" stack is best for lighter saws? Do you reason that the cuter of that size uses less force to cut a trench? on a 10" saw that typically runs 8900 SFPM a 6" stack will run way to slow at 5400 SFPM. or are you talking about little 8" saws?

jack
English machines

[David Kumm]

the problem as i see it is that the washer/ arbor flange have re leaved centers and only bare on the outer edge of the washer flange. If you only use the nut you will distort the the saw plate. Is this a big deal on a small dado plate of 8" or less? Not likely.

Dave How is it you think a 6" stack is best for lighter saws? Do you reason that the cuter of that size uses less force to cut a trench? on a 10" saw that typically runs 8900 SFPM a 6" stack will run way to slow at 5400 SFPM. or are you talking about little 8" saws?

jack
English machines

Jack, I've no scientific proof. Just cautious of build quality of contractor saws or portables like the Bosch. If the arbor is short it tells me the manufacturer doesn't want a dado in the first place. It is the weight of the spinning mass and the force on the arbor that concerns me. I've been around old iron saws so long that new saws look kind of anemic to me underneath. Just me. I do run a 6" Forrest on my Knapp slider, but that is because i would have to remove the dust shroud every time and that is a pain. I don't see any difference in cut quality from my 10" Forrest so the tip speed has never been an issue. I'm also a used guy and 6" show up for a pretty good price. Trying to find a 12" for the Whitney is a tough go, used. Dave

[George Bokros]

Finally found my saw manual. It states I can go up to 13/16" dado and do not have to use the washer (they call it collar). It does not say what diameter dado set is acceptable. I have a Freud 8" set. The saw manual does say the dado max cut depth is 1 3/8". I do not know if that is the max cut on a 6" set or an 8" set, any one know?

Maybe my set diameter is too large for my saw. I do not have any load issues cutting a dado 3/4" wide 1/2" deep in one pass.

George

[jack forsberg]

I do run a 6" Forrest on my Knapp slider, but that is because i would have to remove the dust shroud every time and that is a pain. I don't see any difference in cut quality from my 10" Forrest so the tip speed has never been an issue. Dave

Dave does the Knapp have a 3 speed drive? if so what speed are you running it at? Saws can run a fare bit faster up to 18000 SFPM on large direct drive 18" saws( mind you the blades blows your hair back). I have a tag on the Wadkin PK that states to tension the blade for 3600 RPM. Mind you not many saw shop hammering blade plates any more.;) Optimum seem to be around 10000 SFPM for good cut and tool life. What I posted for a 10" saw is close to that. It looks as if the chop saws(light plastic toys)have taken this and are running much faster than the TS some 5500 RPM , most likely for a better cut in finish work.I would agree that the smaller saws do seems a bit light and i would never go beyond what the manufacture recommends. That being said My general 350 is a solid kit for a 10" saw and its arbor does not fit a 3/4 stack with the washer.

anyway food for thought.

jack
English machines

[David Kumm]

Jack, I might be overly cautious so everyone needs to make up their own mind. My Knapp is single speed, about 4500 rpm I think. The General 350 is a great old saw and light years stronger build than many saws out there. I have a Hammond Trim saw that I speeded way up due to it's 8" blade and since it only crosscuts I like it fast-5500-6000 rpm. When I get the Whitney running, the Hammond will likely go. No dado capability or tilt on the Hammond. Dave